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Thread: i gotta ac problem /:

  1. #1

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    i gotta ac problem /:

    the compressor wont kick on unless you run a wire from the clutch to the battery,we tried jumping the pressure switch and that didnt work,its charged up all the way,but it really doesnt blow that cold. is there a common problem with the ac in these trucks?? what else can i look for to get it to come on??

  2. #2


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    The 86 dealer manual calls out this:
    Compressor clutch inoperative:
    temperature sensing unit defective,
    Clutch coil burned out, or disconnected,
    Defective pressure switch/ replace,
    Defective solid state temperature control/ see component section for diagnosis and repair…



    I’m guessing here, You should be able to check the sensing unit with a ohm meter. It should read out something while warming in your hand.
    You jumped it and some cool air came out, My second guess is the sensing unit.

  3. #3



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    Is the high side real high and the low side at zero - it could be the expansion vale is plugged. Has the drier ever been changed - the dessicant beads can break down and turn to mush and clog the expansion valve. Also if the system has been converted to r-134, too much oil can cause problems
    Pennyman1
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  4. #4

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    i probably shouldve said its a 95 and came 134,im not sure whats been changed but i havent messed with it since i got it,is there a high pressure switch?

  5. #5



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    It might have one - depends on the manufacturer of the compressor if it had just a low pressure only switch or a combo hi/low switch. Since you jumped out the switch and it still didn't engage the clutch, it does sound like the A/C module is the culprit. If you have a volt meter, unplug the pressure switch and check across it for continuity, if the pressure is within range, it should be closed and reading continuity.
    Pennyman1
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  6. #6

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    I had a similar problem with mine. It would sometimes work, then just quit. It turned out that it was the relay under the hood. It had rust in it, meaning that at one time it had water in it. The problem with that was water should have never gotten in it, since it had always been in it's holder, and right-side up, never upside down. It didn't make any sense.

    However, before my dad and I found it, we had used jumper wires also. It worked that way, but in the process it shorted-out the a/c module. After we replaced the relay, we wired it so the a/c would at least work, although the clutch wouldn't disengage, and the engine would bog down going up hills. Plus, you couldn't leave the a/c on while the enginge was idling. The pressure would build up 'til it would blow the pop-off valve on the compressor. That happened once, and it completely blew out the rubber seal on the valve. So, to solve the problem, I had to find another a/c module.

  7. #7

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    You'd think that it wouldn't be too hard to find an a/c module, but, for me, it turned out to be a hassle. People at parts stores and salvage yards looking at you like a monkey staring at a math problem. "Do you mean the a/c controls in the dash?" "No, dumbass, the module is under the dash, mounted on the evaporator core housing." "I ain't never heard of that." *facepalms*

    And the ones that did understand, didn't have it, or couldn't order one. I finally lucked out, and found a salvage yard that had one. I think I paid around $28 for it, which is a darn good deal, I think. My a/c works like a dream now. (By the way, my dad has admitted that he shorted out the old module, when he accidentally touched the wrong wire to the wrong place. Make sure you don't do that, too.)

    Man, I hope what's ailing your truck is something simple and easy to fix. I wish you nothing but the best of luck finding it.

  8. #8

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    thanks bro
    but wheres the relay? and i had no idea there was an ac module,i probably couldve kept that off of my parts truck

  9. #9



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    If its like the 1st gen, its on the top of the evap box on the pass side - pull out the glovebox to get to it. The temp sensor in the evap box may or may not be hardwired into the module.
    Pennyman1
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  10. #10

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    well i spent today trying to figure it out,and it isnt the pressure switch,relay,controle module,or the switch,its got freon ans it still wont work,im going to be pulling the dash out soon to get a good look back there,hopefully its simple

  11. #11

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    anyone knows there the thermostat is? im going to try to swap that out,also the wiring diagram in the haynes book doesnt show the ac control module for some reason,anyone know of some FSMs online?

  12. #12



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    On my first gen the temp control is the little ring around the outside of the fan speed control knob.
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  13. #13


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    I'm reading through my factory repair manual, reading through the steps knowing you have jumped the clutch. I got to here and it said to check the clutch relay with an ohmmeter, check continuity per wiring diagram which it calls out for blue (1.25 mm wire to the relay). (1st gen manual). The relay is the ground.
    I don’t know where mine WAS located? When you find it, turn the ac on and off having some one touching it. They should feel it clicking. Pull the plug clean it and plug it back in and try it again.

  14. #14

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    Quote Originally Posted by onelozu View Post
    thanks bro
    but wheres the relay? and i had no idea there was an ac module,i probably couldve kept that off of my parts truck
    The relay is under the hood, on the driver's side. It's mounted on the fender, actually, the holder for the relay is. It's mostly rubber, with a metal mounting tab. Both the relay and the holder are round (at least on mine it is), so it shouldn't be hard to miss. I'll look at mine in the morning to double-check, and if I can find that crap camera of mine, I'll take a pic of the relay and post it here for you. If I have time, I'll try to get one of the module, too.
    Last edited by Stunner; 07-07-2011 at 11:06 PM. Reason: Brain fart. There is no strut tower. :shakehead:

  15. #15

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    Quote Originally Posted by onelozu View Post
    well i spent today trying to figure it out,and it isnt the pressure switch,relay,controle module,or the switch,its got freon ans it still wont work,im going to be pulling the dash out soon to get a good look back there,hopefully its simple
    You might get away with just removing the glovebox. You'll have a pretty good view of the evaporator housing and the blower housing. Like pennyman said, the a/c module is mounted on the evaporator housing. It can be a pain to get to the screws, thankfully only two hold it on. If you need to remove anything, say, the blower motor housing, don't forget to remove the bar the glovebox mounts to. You'll need it out of the way. I decided to clean the evaporator and the blower motor, plus the housings, before putting the replacement module on, and that's what I had to do. I also had to replace the foam on the inside/outside air vent door. One side had rotted, and the other had a spot where mice had chewed on it.

  16. #16

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    And as far as manuals go, I may have a few wiring diagrams that might help you out. I also had a hard time finding anything on the a/c modules, but maybe these might do you some good. I'll have to go find them first, but I should have them on here tomorrow.

  17. #17

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    My camera isn't working right, ' cause it's a piece of crap, so I won't be able to post any photos. Sorry about that. I still plan on posting the wiring diagrams when I find them, though, so maybe I can help you out a little.

  18. #18

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    It might be a long shot, but I fixed mine with the same symptoms by spraying electrical contact cleaner into the A/C on/off switch in the dash. Going on a year and a half since that with no problems.

    RD

  19. #19

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    Finally found them, although there are only two. They are for a '92 Ram 50, but maybe they'll be of use to you. I also have two for an '88 Ram 50 that I'll post. They won't help you that much, but maybe they can help someone who has an '88 model, or close to it.

    Click image for larger version. 

Name:	92 Ram 50 Column Switch, Cruise Control, AC System.jpg 
Views:	4382 
Size:	46.9 KB 
ID:	917Click image for larger version. 

Name:	92 Ram 50 AC-Heater Wiring Diagram.jpg 
Views:	2638 
Size:	37.8 KB 
ID:	919Click image for larger version. 

Name:	88 Ram 50 Fuse Block.jpg 
Views:	2013 
Size:	46.3 KB 
ID:	916Click image for larger version. 

Name:	88 Ram 50 AC-Heater Wiring Diagram.jpg 
Views:	3643 
Size:	29.4 KB 
ID:	918

  20. #20

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    how do i blow up the pics?? i zoomed but it got blurry lol
    i was testing wires to see where i have power and the fan stopped working and every fuse is still good
    also one thing i was getting a lot while checking wire is if you ground the wire on the test light,theres a lot of wires in the ac circuit without power,but if you go from the positive of the battery(like testing grounds) almost all of the wires have power,whats up with that??

  21. #21

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    Hmm... Sorry about that. I uploaded them to my Photobucket account, so you should be able to see them now, full-size. Here is the link. As for the remaining questions - I'll try to have some answers for you tomorrow. I'll ask my dad, who's forgotten more about working on vehicles than I'll ever know. He has close to 40 years of ASE certified experience, so if I can't get some answers from him, then I don't know what to tell you.

  22. #22

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    thanks bro! i really appreciate all the help im getting on this site!

  23. #23



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    you might have a bad ground to your A/C system hence the funny readings with your test light

  24. #24

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    To check the blower motor out, you need to unplug the connector that plugs into the blower resistor, located on the bottom of the blower housing. The connector has 4 wires that go to the resistor, each one corresponding to a different fan speed. Take your test light, connect it to a good ground source, and with the key on, start with the low speed setting. Touch each wire in the connector with your test light until you find one that makes it light up. If you do, continue on with the next speed setting, repeating the process until you go through all the speeds. If each wire lit up on a different speed, your fan switch is good, and it's time to move on to the resistor. Plug the connector back into the resistor. There are 2 wires coming from the resistor, the hot wire that goes to the blower motor, and the ground wire. Check the ground wire first, making sure that it is secure, and properly grounded. I moved my wire, and fastened it directly to the body, ensuring I had a good ground.

  25. #25

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    During reinstallation of everything, my blower wouldn't work until I did this. Now, if your key is still on, along with the fan switch (on any speed), and your blower starts working, then problem solved. If it doesn't, then it's time to check the hot wire coming from the resistor. With your test light grounded, and key and fan switch still on, touch your test light to where the hot wire connects to the blower motor. If it doesn't light up, your resistor is bad, and needs to be replaced. If it does light up, your resistor is good, and your blower motor is bad. You might get the blower working again by lightly tapping on the bottom of it with a hammer. This is in no way a permanent solution, as the blower will still need to be replaced. This should help you solve your blower problem. As for the rest...

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