Trying to Get My A/C System Through the Summer (Part II)
A few weeks ago, I wrote a piece about “the good kluge.”
Just so we’re clear, what I describe below is not one of them.
Last week, I talked about the A/C in my 2008 Nissan Armada having a leak that was small enough that I could keep topping it off with a can of R134a about once a month. The leak, discovered by using dye and a U/V light, was in the condenser, a part that costs about a hundred dollars but is a non-trivial amount of work to replace due to the way that the radiator, condenser, transmission cooler, and fans are packed in the nose. Unfortunately, the A/C also would mysteriously switch off. It was unclear to me whether or not the two problems were related. I wanted to defer the condenser replacement until fall, but I also wanted working A/C.
When the shut-off problem initially cropped up, it was a mid-level inconvenience. I was barely using the truck anyway. It had been mostly sitting at the end of the driveway waiting for me to use it to snag and tow home some cool car, which has more to do with my self-image than actual reality or need. But then a good friend of mine had some personal issues that resulted in my loaning him my daily-driver 2003 BMW 530i. While I have several air-conditioned vintage cars, keeping them out of traffic and rain and in compliance with the terms of my Hagerty policy has meant that the Armada and its wonky A/C system has been pressed into service.
![Hack Mechanic AC System 635 csi](https://hagerty-media-prod.imgix.net/2024/07/Hack-Mechanic-AC-System-IMG_8923-scaled.jpg?auto=format%2Ccompress&ixlib=php-3.3.0)
I ran the system multiple times and verified that, when the A/C worked, the reading on the red high-side gauge increased and that on the blue low-side gauge decreased, validating that the compressor was doing its thing. The high-side reading, though, appeared to be slightly lower than what the A/C section of the Nissan factory service manual (FSM) listed it should be for 90° temps, likely indicating that the system was slightly undercharged. Unfortunately, it’s not really feasible to drive with the manifold gauges attached and placed where you can safely see them. You need to instead infer the operation of the compressor by the vent temperature. This seat-of-the-sweat-glands method told me that, when it got toasty in the car, the compressor wasn’t, uh, compressing. This was confirmed by stopping, popping open the hood, looking down at the compressor, and seeing that the magnetic clutch wasn’t engaged (the pulley was spinning but the nose that pokes through it was stationary).
Usually, as part of this test, you’d verify that voltage is reaching the compressor, and maybe hot-wire it to the battery to make sure that the clutch engages and it comes on. Unfortunately, the connector on the Armada’s compressor is very difficult to reach, and is one of those little Japanese puzzles where you need to depress a tiny tab with a fingernail while you pull the halves apart. I eventually managed to separate it, but instead of finding a standard flat quick-connect terminal, there was a tiny pin with no easy way to connect to it. So instead, I used one of those wire-insulation-piercing splice adapters that are often used to tap into key-on accessory wires to install a radio. Really, I recommend that you not do this, and I strongly recommend that you not drive a vehicle this way, as you’re defeating sensors that are in place to protect the compressor and the A/C system as a whole. But I found out what I needed to, which was that with the compressor running, the system began blowing cold again.
So, something was shutting off the compressor. But what? Last week I showed a couple of diagrams from the factory service manual and quoted the description of the complicated relationship between several control modules and half a dozen sensors that results in compressor turn-on or its failure. I read a cluster of posts on the Armada forum implicating the evaporator “intake sensor” and listing symptoms identical to mine that went away with its replacement, but swapping it out ($60 and ten minutes) made no difference.
The next-most suspect sensor was the pressure sensor screwed into the receiver-dryer, which on this vehicle is an integral part of the condenser. On older vehicles with A/C, these are simple, easily-bypassed switches that cut off voltage to the compressor if system pressure is too low, indicating a big leak, or too high, indicating a blockage. But on newer vehicles like the Armada where the compressor is managed by a control module, they’re sensors, not switches—that is, they report actual system pressure back to the control module which then makes the decision regarding whether or not to send voltage to the compressor’s magnetic clutch. The one on the Armada is a three-wire sensor with the wires being ground, a 5V reference voltage, and the signal from the sensor. You can’t simply bypass the sensor with a jumper wire, as either doubling back the 5V pin into the signal pin or grounding it at best sends the control module an out-of-range pressure reading, and at worst risks damaging the module that’s reading it.
But what you can do is fool the system by sending it a reading that the vehicle’s electronics interprets as a valid A/C system pressure between 17 psi and 292 psi. The trick is to use two 1.5-volt batteries in series, as a 3-volt reading corresponds to a pressure within the acceptable range. I don’t recommend that you do this because if you get the wiring wrong, you can blow up the a/c control module, but I was willing to take the risk. So after spending $5 for a battery holder, carefully using a multimeter to verify which of the three pins on the connector were 5V, signal, and ground, tinning the ends of the leads with solder, carefully inserting them into the signal and ground sockets on the connector, and hitting the switch on the battery box, the compressor engaged and the condenser fan turned on. I used a sloppy wrapping of electrical tape to temporarily hold the leads in place while I test-drove the car.
![Hack Mechanic AC System relay](https://hagerty-media-prod.imgix.net/2024/07/Hack-Mechanic-AC-System-IMG_8797-scaled.jpg?auto=format%2Ccompress&ixlib=php-3.3.0)
Let me interject here that there’s a distinction between the compressor short-cycling, which is the pressure switch turning the compressor off when the refrigerant level is low because the low-side pressure drops too low and then turning it back on when it rises, and the A/C turn-off that my Armada was experiencing. And, yes, I admit that the refrigerant was, or could have been low, as the system definitely did have a slow leak. Short-cycling, though, tends to repeat at intervals more like several times a minute, whereas what I was experiencing was the A/C shutting off and not coming back on again until I did something like parking and restarting the car. Do-it-yourselfers like me often bypass the pressure sensor, or hot-wire the compressor when filling an empty system to speed up the delay caused by short-cycling.
But as far as fixing my shut-off problem, my AA-battery-box pressure sensor bypass made no difference. After driving for maybe ten minutes, the vent temperature gauge rose, and stopping the truck and popping the hood verified that the compressor wasn’t engaging. The same thing happened on repeated tests. So it appeared that the shut-off was neither due to short-cycling due to the system being low on refrigerant from the leak, nor from some other pressure issue being flagged.
I wondered if perhaps it was as simple as the relay controlling the compressor clutch having some heat-related problem. The relay is drawn in the A/C system layout as if it’s a separate part. Unfortunately, when I searched on the Armada forum to determine the relay’s location, I learned that it’s an integral component of the Intelligent Power Distribution Module (IPDM). Strangely, whereas the IPDM is a collection of fuses and relays, the compressor relay is a non-removable part of the module and is not independently replaceable. If the relay is bad—and I didn’t know if it was—you need to replace the entire module. New, it’s about $500. Used ones are available on eBay for about $100, with no guarantee that they don’t have the same issue. The same was true of the A/C control module (the oddly-named “A/C amp”), which was also widely postulated as “maybe it’s this” on the Armada forum.
I delved back into the forum and saw numerous posts where others experienced similar A/C-shuts-off problems similar to mine (absent the slow leak), analyzed it with scan tools, replaced the IPDM and/or the “amp” or had the dealer do it, and it made no difference—some sensor was still causing the amp to shut down the compressor, but they could never figure out which one.
I thought about it carefully, as I do most things (I’m not the unhinged whack job that I sometimes appear to be).
While I’ve run my vintage cars with the compressor hot-wired, I really didn’t want to do this to the Armada, as it’s a complicated system and bypassing everything felt like disabling all the safety interlocks on a train. The risk in driving a car with the compressor hot-wired is that you run it low on refrigerant and/or oil and seize the compressor, which typically causes it to throw metal and rubber debris into the system. To resurrect a system after this happens, the compressor, parallel-flow condenser, and receiver-dryer all need to be replaced, and the remaining components (hoses and evaporator) need to be flushed out. But since there’s an expansion valve in line with the evaporator that you can’t flush through, it means that the evaporator core needs to be removed to be flushed. And this vehicle has rear air, so there are two evaporator cores. So if I was keeping the Armada long-term and needed the A/C to work, risking compressor seizure for short-term usage was foolish.
On the other hand, there was no way I was going to bring the vehicle into a dealership and pay them for a full A/C diagnosis and repair, as the cost could easily approach the vehicle’s value. This is a 182,000-mile Armada with a non-trivial amount of undercarriage rust and a whole variety of quirks and needs. I’ve already admitted that buying it was a mistake. Even with all the work I’ve done on it since buying it last winter for $3250, I doubt I’d get three grand for it. I’ll probably quasi-justify its existence by using it to tow my 1973 BMW 3.0CSi to and from a paint touch-up, and dragging my barely-running ’75 2002 back from storage, then sell it in the fall. It’s difficult to imagine that, if I seize the compressor, that will be the single thing that torpedoes the vehicle’s value.
Decision: For now, hot-wire the damned compressor. Well, wire it to a switch so you can directly turn it on when the Armada’s internal climate-control Skynet fails. And check the system pressure before you use it.
The switch part of it turned out to be a bit tougher than I thought because passing wires through the firewall on a modern vehicle is a lot harder than doing it on a 50-year-old car with saggy grommets that you can see light through, and where the challenge is keeping engine smells out of the vehicle. Fortunately, there’s a whole class of remote-controlled electrical relays (which is ironic because relays are, my definition, remote-controlled switches). For $16, I found a little remote-controlled switch box which I could mount in the engine compartment, wire with input voltage from the battery and chassis ground, connect the output to my spliced-in wire to the compressor, and turn on from the inside of the truck with a little key-fob-type remote.
![Hack Mechanic AC System switch](https://hagerty-media-prod.imgix.net/2024/07/Hack-Mechanic-AC-System-IMG_8904-scaled.jpg?auto=format%2Ccompress&ixlib=php-3.3.0)
My mounting scheme is currently having the relay in a Ziplock bag taped to the lid of the fuse box. It’s just enough to be functional. And yes, it’s wired with a fuse.
![Hack Mechanic AC System electrical tap](https://hagerty-media-prod.imgix.net/2024/07/Hack-Mechanic-AC-System-IMG_8908-scaled.jpg?auto=format%2Ccompress&ixlib=php-3.3.0)
I took a little break from the compressor problem to look at the “woodpecker under the dash” issue. Like many modern climate-controlled cars, actuators move the flaps on the Armada that control the blend of hot and cold air and its distribution through the front-facing, defrost, and footwell vents. It’s common for something—a gear inside the actuator, or a piece in the linkage between it and the flap—to break. The result is often the actuator motor continuing to spin when it shouldn’t, causing the teeth on plastic gears inside it to skip and make a sharp clicking sound. The Armada has three of these actuators on its climate control box. If the clicking is coming from the one in the center, the FSM directs you to remove the entire dash, with YouTube showing a variety of workarounds to avoid such an invasive job. Fortunately, the one that was clicking on mine was the easy-to-reach one for the passenger-side blend door. The fasteners are accessible if you have a 5.5mm ratcheting wrench. I yanked it out and found that the problem was that the little triangular plastic stop tab that sits on the cam-shaped plastic plate between the actuator and the lever had broken off. Multiple posters said they tried to epoxy the broken-off stop, only to have it immediately snap off again, so went to order the part. Oddly, the actuators are fairly inexpensive and available from dozens of manufacturers and vendors, but this particular intermediate lever is a Nissan-only item that had gone out of production, meaning that I had to hunt around for a dealership that had one in stock. $40 and a one-week wait from California got it here. It didn’t help main A/C problem, but at least it got the woodpecker to shut up.
![Hack Mechanic AC System wrench nut](https://hagerty-media-prod.imgix.net/2024/07/Hack-Mechanic-AC-System-IMG_8917_equalized_annotated-scaled.jpg?auto=format%2Ccompress&ixlib=php-3.3.0)
![Hack Mechanic AC System black plastic cover](https://hagerty-media-prod.imgix.net/2024/07/Hack-Mechanic-AC-System-IMG_8912_annotated.png?auto=format%2Ccompress&fit=crop&h=480&ixlib=php-3.3.0&w=640)
I learned that there was a fourth actuator on the heater control valve against the firewall under the hood. This is supposed to shut off the flow of hot coolant to the climate control box when the a/c is on high. I drove the truck and then laid my hand on both the box and the hose exiting the valve, and could tell that it they were staying hot, so I pulled the cover off the actuator. It’s designed so that you can remove the rod connecting the motor to the valve and rotate the valve by hand. The valve felt sticky. For now, I simply rotated it closed and left the control rod out. I verified that the climate control box no longer had a little furnace running inside it. When the a/c was running, this may have made the vent temps a degree or so colder, but it had no effect on the compressor shutting off.
![Hack Mechanic AC System flow sensor](https://hagerty-media-prod.imgix.net/2024/07/Hack-Mechanic-AC-System-IMG_8907_annotated.png?auto=format%2Ccompress&fit=crop&h=480&ixlib=php-3.3.0&w=640)
So, one unforgivable kluge (the remote-controlled compressor switch), two pretty decent ones (the battery-powered pressure sensor bypass and the manual closing of the heater valve), and one absolutely correct repair (replacement of the intermediate actuator plate). It averages out to be almost defensible. But I feel that what I’m doing with the remote compressor switch is taking data. I can continue to drive the Armada with the normal climate control, note what’s going on when the cabin temperature rises even though the A/C light is on, shut the A/C off so I don’t risk back-feeding the relay with voltage, then remotely turn the compressor back on.
But seriously, on a car that you value, don’t do what I did with the compressor.
***
Rob’s latest book, The Best Of The Hack Mechanic™: 35 years of hacks, kluges, and assorted automotive mayhem, is available on Amazon here. His other seven books are available here on Amazon, or you can order personally inscribed copies from Rob’s website, www.robsiegel.com.
“almost defensible” seems better than “hot & muggy” I guess. LOL
This got to the point where a modern scan tool with live data would be key.
You could check if the IPDM is commanding the compressor to engage, and if it did then I’d crack the module open and solder in a new relay. If not then you could read the live data from all the A/C input sensors and try to find the culprit.
I agree, but I don’t have one, and am unsure if I’ll be keeping the truck long enough to justify buying one.
I get it, probably too much investment for this particular case.
The one thing you could do on the cheap with a DMM is to probe the relay on the board, checking whether the coil is being energized when the compressor fails to engage.
But then again, this is likely way easier said than done 🙂
“I am not the unhinged whack job that I “sometimes” appear to be.”
Never change, that is why your loyal readers come here weekly to see just how far you stretch the unhinged part…..
Thanks Helen!
Ditto to Helen C. When one of my various car challenges seems to get to me, I take a break. Find an older Rob Siegel column to read. After awhile, I think my problem doesn’t even come close Rob’s, let get back in. Please never ever change, Cheers
Have you cracked open the IPDM? As Federico mentioned it is highly possible that the relay is a through hole component that can be relatively easily de-soldered and replaced. My favorite cars Ford’s Panthers use a Lighting control module that includes a relay soldered to the board which many people have replaced on their own, some even get a standard relay socket run wires to it and mount it externally. I’ve also done it on GM’s wiper modules and even on the control system for my friend’s wheel chair lift. They almost always have a part number on them and even if you can’t get an exact replacement there is always running wires to an external socket.
I only see one major mistake in all of your actions here: the friend should be riding around in the Armada, not the BMW! 🙂
Curious if a live scan tool will tell you the sensor that trips the compressor? Seems like (from what I dimly remember) the PCM gets a signal from many sources, so theoretically the PCM should tell you which one is tripping it. This may be worth the shop time just to diagnose?
Why diagnose it properly, when you can spend 100’s of dollars guessing at it. Makes perfect sense if you’re an idiot
This vehicle and attempts to repair is like watching ritual Seppuku you can’t stop.
Honorable but not really worth the cost.
Hmm at least you did not buy a Sameri.
Those inexpensive remote controlled relays are handy for a lot of things. When the receiver on my vintage 1976 garage door opener died, but the opener itself was fine, I bought one of those relays and three transmitters for $24. A half hour’s work and my opener is ready for another 48 years.
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Even though it would be unforgivable on any decent car, hey, it’s a Nissan. I’d have gone with cheap air, too.
You have to admit that this Armada is the gift that keeps on giving! (stories)
Thank you for once again reminding me why my DD is a 34 y/o 245
I would step back and punt. A loss of this truck and some dough would be worth my sanity.
My 1963 Rambler kludged together system is much simpler! Basically it’s wired like the 63 system… no safety pressure switches at all. I should probably wire a binary switch into it. There are switches that screw onto the service port, so really no reason not to (just lazy…). If it were a daily driver I probably would (and may still…), but it was retired from that around 2013 (after 10 years of it). I have the 63 evaporator and expansion valve, 1990s Sanden compressor (engine is a combo of AMC/Jeep 4.0L parts of various years), universal drier, and 1990s Chrysler LH parallel flow condensor. It all works well together, connected by custom hoses since the 63 parts have flare connections and everything else has O-rings. Had to cut the line tubes on the condensor and have fittings soldered on due to the way the factory lines connect. The electrical controls are all 1963. The blower switch also switches on the compressor. There is a temp control but that is shot — I really need to fix that “one day”. I haven’t because the 63 designed system isn’t like a modern one. The evaporator in the station wagon is just big enough to keep you from sweating when outside temps get over 90 (with SC’s 40-90% humidity in summer!). Not exactly as comfortable as you’d like (and I have tinted windows all around, darker in the cargo area), but not uncomfortable either. So it’s on high cooling pretty much all the time from late May to mid September. I have considered using an aftermarket evaporator, but the couple companies I talked to said they don’t have anything that would cool that wagon much better (if any) than the factory setup. Too much work if little to no gain!
The Rambler’s ventilation system has enough airflow to keep the car comfortable without AC (as long as you’re moving) if the outside temp is under 80. That is if you know how to use it — trying to flip the vent windows around so they become “air scoops” IS NOT the way they are intended to work!
My Dad had a 63 Rambler Classic I can’t remember if it had A/C or not but why wouldn’t you flip those wing widows around? That’s what they are there for and his next car was a 65 Marlin had the same setup since it was a Classic body
A wise man told me once, “If you buy _ _ it, it probably is going to stay _ _ it, until you put a ton of time and money in it.” Thanks, Rob for reinforcing that message. However, it sure is entertaining to read your stories and the rationalizations on why you buy these gems. I learn something every time I read your articles or trials and tribulations you encounter along the way.
Hmmm
I often enjoy reading about folks here on Hagerty that tackle odd vehicle repairs whether for fun and satisfaction or just to save money. Most are entertaining and educational.This however was a bit painful to read.
Here, a lot of “jerry-rigged” modifications that have yet to solve the issue. Rube Goldberg yes, problem solved, no. I wonder if borrowing a high end, quality OBDII scanner, purchasing a Nissan Factory shop manual or paying someone to do that scan, may have shed light on the exact culprit. Even a visit to a Nissan dealer or a Nissan focused independent repair facility or an A/C specialty shop for no more than a diagnosis charge, would have made a world of difference. Let someone diagnose and you do the fix. Shot gun replacement of parts today is quite expensive and very defeating. Offering band aids here at best but good fodder for this article, yes? Since you probably get paid to write this, maybe use some of that money to help diagnose it and let others know what the actual issue is? That would be helpful. Oh, and for heavens sake, replace that condenser, it is leaking and adding a can of refrigerant every month that just escapes into the atmosphere is not prudent nor a solution.
I think we all like to putter around with our cars but when the puttering is clearly failing, repeatedly, it is no shame to ask for or search for qualified help. Would all of the time lost on this A/C issue so far, (now on Part II and counting) have been better spent with family?
I mention time because of an older gentleman’s pursuit of the perfect restoration of a Corvair convertible that played out on another blog. This man was the definition of obsessive-compulsive as regards his restoration. The time he spent doing and then re-doing and then re-re-doing almost every aspect of this restoration was enormous by his own accounting and mind boggling to his readers, not to mention the money factor. It made for fascinating reading and folks were anxiously awaiting the next long chapter of his exploits. After so many starts and failures and re-do’s and do overs, he admitted being down at times but he pressed on and pressed on. Every part had to be NOS or as perfect as he could possibly get, often buying duplicate parts to find the best among them. Absolutely amazing energy and focus for an older gentleman tackling this restoration, pretty much on his own.
At one point I commented to him online, asking how his wife was handling all of this restoration and re-do’s along with his high’s and low’s and I suggested he go purchase a decent used Corvair convertible just to take her for top down spins now, as a reward, as he mentioned he would do “someday”. He replied in the blog that he planned to finish “his” Corvair to do just that with her and to win an award at a local Corvair Club and that she was fine with his project. As it turns out, he did not quite finish his Corvair but from the last pictures presented, it was a very beautiful car. A few months later, that Corvair was featured on the same blog’s “cars for auction” site. In the description about the Corvair, it was disclosed that “illness” forces the sale. I don’t know if he or his wife became ill, if his car was ever entered at his Corvair club and I can only hope, that his wife got to ride in this Corvair with the top down before it was auctioned off. Extremely sad.
This gentleman and his amazing venture into the restoration of that Corvair happened to change how I view my priorities. Reading everything he posted and seeing what eventually transpired, struck a chord. I look at life a bit differently now due, in part, to this man. I hope he and his wife are well.
Life is much shorter than we all realize.
How valuable is your time?
Sometimes, we just need to accept the benign choices someone makes, in which purpose is expressed, however poignant. I’m beginning to learn, we all eventually experience, age relentlessly limiting opportunities, and levels of activity, narrowing the available avenues of pursuit.
well now i have a good idea of what happened to my actuator on my hhr when i changed the cabin filter a few years ago that prob had never been changed…. doubt it’s easy to replace it.
your troubles with the altima in disguise is another reminder of why most newer cars suck big time being overly and unnecessarily complicated and basically designed to be short lived trash. Incredibly wasteful. It’s all about greed imo. not at all about pride in workmanship of the product.
humanity needs a radical shift in mindset back to when people cared about making something built to last