Hey guys, I appreciate so much how so many people share their ideas and fixes for problems. I learn a lot here and save a bunch of money. Now it's time to give back.
I recently started having my AC compressor just stop working – vents started blowing hot air. I could turn off the AC button on the dash control and then turn it back on and sometimes the compressor would stay on for hours, sometimes just for a few seconds. It's in the 90's in GA and that got real dang old real dang quickly. I did what everyone does and checked the freon, even added a bit. It was fine of course but had to try. Also jumped voltage straight to the compressor from battery and things were great. Hooked it back to the wiring harness and same old problem reappeared.
Then, I started reading here on the forums and some other places and realized that it was my compressor clutch solenoid. Specifically, when they start to get worn, the electrical current (amperage) required to engage it goes up. At some point, it exceeds the 3 amp maximum output of our TIPM (overglorified current sensing relay) and our computer just says it's pulling too much amperage and just stops trying. Then, the system starts blowing hot air again. Since the compressor clutch itself is not serviceable, everything indicated that I would have to buy a new compressor and go that route. August 24, 2011. See note at end of post. Replacement now available!
Two things bothered me about this. 1. My compressor was still sealed just fine, not leaking Freon, and provided very cold air when it worked. 2. It really peed me off to have to buy a new compressor just because sometimes the clutch coil pulled a little more current than my computer thought it should.
In thinking about this and sweating profusely, I thought “ya know…I don’t have a compressor problem, I have a clutch amperage problem. And if I provide heavier current to it and it ultimately craps out, who gives a rip? It’s already kinda crapped out now!” So in that light, here’s what I did. 7 months later…it’s working like a champ. Might die tomorrow but it worked today!
I installed a separate current path for the clutch coil via a 30 amp relay and then used the truck’s factory wiring to trigger this relay. This way, the TIPM never sees more amperage than it takes to pull in a relay (about .1 amps) regardless of what’s going on in the compressor coil. Now, the computer never sees the increased load that my clutch sometimes pulls and therefore never tells it to turn off.
This is how I did it:
1. Disconnect the vehicle wiring harness from the compressor connector
2. Identify the positive terminal in the vehicle wiring connector – this can be done with a multimeter or test light
3. Crimp a terminal to a piece of insulated wire (16 gauge or heavier – about 3’ long) and then modify the end of it to push into the positive terminal on the vehicle connector
4. After connecting the wire to the vehicle connector, I wrapped the joint heavily in black tape to seal it and also to hold the wire/terminal in the connector
5. Next, I repeated this wiring scenario for the compressor side connector except that this one has to have two wires – one for ground and one for 12V+ from the new main relay – about 3’ long each – you can cut if needed later. The second wire for the ground is important as the clutch will NOT ground through the compressor body/chassis. It MUST have a separate wire run from the ground terminal in the connector to a chassis ground.
6. With the positive wire run from the vehicle connector and the positive and negative wires run to the compressor, I then installed a 4-terminal relay from Autozone near the battery and air intake. Two terminals of the relay pass the heavy current from the battery to the AC compressor wiring harness. The remaining two terminals serve as the “trigger” part of the relay and connect to the wiring harness of the vehicle.
7. I bought a fuse holder/wire (10 gauge) from Autozone and attached it to the positive terminal of the battery with a ring terminal. I crimped a blade terminal to the other end and plugged it into the relay. The 12V+ wire from the compressor plugs into the terminal exactly opposite the supply voltage.
8. The remaining two terminals are the trigger part of the circuit. One of these terminals uses a short wire to the negative battery post or chassis ground. The last terminal receives the 12V+ wire from the vehicle side of the wiring harness connector.
9. With all of the wires attached, the system is now intact except for the empty fuse holder. I originally plugged in a 5 amp fuse. After a few minutes of use, it blew. So, I replaced it with a 7.5 amp fuse which lasted longer but finally also blew. I then said “screw it” and installed a 15 amp, auto-reset breaker in place of the fuse. These plug in exactly as a fuse does. Should the current ever exceed 15 amps, the breaker will trip and stop passing current. Then, I will simply cycle the AC switch on the dash to automatically reset it.
I can’t say that this will work for everyone but it worked for me. My compressor was working fine but the clutch was sometimes pulling more current than the TIPM wanted it to. In my mind, it was already screwed up so I didn’t really care if put a little more current on it than Dodge thought prudent. So far, it has worked and I am extremely thankful for that. I’m sure that I’ll get around to replacing the compressor when the clutch eventually craps out. In the mean time though, it cost me about $20 of crap, 1 hour of my time, and I have AC in my 2006 Megacab and that’s all that matters to me!!!
UPDATE TO POST: June 5, 2011
Several other folks have used this fix and it has worked for them - yay! However, we have seen another variable in the mix. Once we jump the compressor and determine if it is good or not, the relay system can be installed. IF the TIPM is not totally screwed up, then it will trigger the relay and all will work as described. HOWEVER, we have seen a couple of times where the TIPM showed voltage at the connector but dropped out (turned off) just as soon as ANY load was placed on it - even milliamps for a relay. This totally sucks. If this is the case, then a stop-gap measure can still be taken to get AC until you can have the TIPM fixed, etc. In this case, find a 12V+ signal on the fuse box that only comes on when the key is in the "run" position. Connect this signal to the "trigger +" on the relay. Then, take the "trigger -" (ground) wire and run it into the cab. Mount a simple toggle switch in a handy place and connect this ground wire to one side of the toggle switch. Run a second wire from the other side of the toggle and connect it to a chassis ground (metal) under the dash somewhere. Now, when the truck is running and the switch is activated, it completes the ground for the trigger on the relay and the AC turns on. When the truck is turned off, the compressor turns off too.
USE CAUTION AND DISCRETION if you do this mod!!! It should work fine when you are running on the road and have good airflow across the radiator. If you get stuck in traffic and have little airflow, then the pressures can go high in the system as the pressure switch is no longer part of the circuit. You may want to cycle it manually from time to time in this condition. Good luck!
I hope that this is helpful. Any questions, just post them and I’ll try to get back to you. I have pics that I will post when I figure out how!
Update to post: August 24, 2011
My original clutch coil lasted for about a year after I did this "fix." Then, my clutch coil had just basically weakened/burned up to the point that is was no longer reliable. I ordered a replacement
from Sunair and replaced the coil. This was about 7 weeks ago and mine is working great. I'm still running the external relay and have no plans to change anything. This is also good insurance against taxing my TIPM.
Update to post: September 24, 2012
Relay and AC still working great. My original coil made it an additional year before totally crapping out but some are only lasting a little while longer after the relay mod - we've seen hours and a year and everything in between. When you install the relay, I STRONGLY suggest that you get your replacement coil on order. They are cheap and not bad to install. Just an fyi, the relay will probably buy you some time and it's good to get the load off the TIPM but once your coil starts to break down, it's days are numbered so plan accordingly. Wish you guys the best.
PS the replacement coils were running about 8 weeks lead time. Not sure now. It's cheap insurance to order one. About $70 or so. CC-401
PS Links for high res pics are below:
NOTE: The photobucket link above is for the wiring schematic for the relay if needed.