# ac not working



## skramer360 (Aug 14, 2005)

My ac system is fully charged, but it isn't working. I started the truck pushed the button on the dash and turned the fan on. The light did not light up on the button. I left the truck running and put power to the plug on the compressor and it started running and cooling the air in the truck. Where should I start? Is there a common failure in the electrics of the ac system like the dash switch? Its starting to warm up here and any help would be appreciated.


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## smj999smj (Jan 1, 2006)

Year and engine?


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## skramer360 (Aug 14, 2005)

Ah sorry, its a '95 v-6 4x4.


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## smj999smj (Jan 1, 2006)

First, take a 12v test light and check all of your fuses. If it's not a fuse, we have to assume no power is getting to the compressor clutch since it works when you apply 12v to the clutch. Next you would need to check for power to the thermal protector, aka "thermal amp." I believe you may need to remove the glove box and metal panel behind it to access the plug. IIRC, there's a small, white, 2-pin harness connection for the thermal amp on the side of the AC evaporator case (the thermal amp itself is inserted into the evaporator core inside the evaporator case). If you have power to the thermal amp, you'll then need to check the circuit between the thermal amp and the compressor. If the circuit is good, replace the thermal amp (which means discharging the system and removing the evaporator case). If the circuit is open or shorted, repair the circuit. If you have no power to the thermal amp, then you'll need to check the AC Relay and circuit. At this point it's going to start getting complicated, so I would suggest you consult the factory service manual for the rest of the diagnostic procedure and wiring diagram. If you can't find one online, let me know and I'll see what I can dig up for you. Send me an e-mail at [email protected] if you get to the relay and it's still not working. Something else you may want to do is to check the AC switch for continuity when it's in the "on" position using an ohmmeter or continuity tester.


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## Ding1 (Dec 7, 2012)

I suspect the dash switch,it may be faulty or the plug harness just came off but it may just be a faulty switch.


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## TheRepairMan (Jun 30, 2009)

Ding1 said:


> I suspect the dash switch,it may be faulty or the plug harness just came off but it may just be a faulty switch.


Well, if we are just going to throw out there some wild guesses, I'd say it's the AC relay. 

But guessing at bad parts isn't the way to do this. I'd follow smj's suggestions in his previous post and test everything out.

-R


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## Ding1 (Dec 7, 2012)

Just my way of saying check it is all,after the fuse checks etc,guess I didn't clarify that..He did ask for any help.I am by far no expert.I replaced a switch twice that were the culprits in two vehicles and plugged one back in in mine, what he described fit the problem(s).The no lighting up symptom.My apologies.


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## TheRepairMan (Jun 30, 2009)

Ding1 said:


> Just my way of saying check it is all,after the fuse checks etc,guess I didn't clarify that..He did ask for any help.I am by far no expert.I replaced a switch twice that were the culprits in two vehicles and plugged one back in in mine, what he described fit the problem(s).The no lighting up symptom.My apologies.


No problem. Not busting on you, Ding1. You could be right, but I like to see owners test systems out, or learn test basics before jumping to conclusions. I know I do come across a little coarse sometimes, but like you, I actually am here to try to help, too.

It pays to pay close attention to smj's posts. He knows his stuff!

-R


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## Ding1 (Dec 7, 2012)

Didn't think you were R and SMJ has opened up many insights to my truck problems and some I have been pondering upon and then some from his posts.I did bookmark those links ya posted in another post for future reference FWIW.I read posts for hours to glean knowledge and ideas and sometimes I might think I know something or have experienced it and pass it on.I always wish for the easiest way to fix something for everyone,even me.LOL.With all the knowledge here I am sure he will find the problem.


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## skramer360 (Aug 14, 2005)

I haven't had time to do anything yet. Both my kid's cars needed repair. I've got my son's car done, and still need to work on my daughter's car. I will update this thread when I get it fixed. I'll probably start by checking the relay and the dual pressure switch. 
@ ding, I did take the switch out of the dash and checked it as well as I could with an ohm meter. 
I do also have a FSM, so hopefully that will be helpful.


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## foker (Jul 8, 2015)

Where is the switch located on my 95 Nissan hard body ?


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