A/C control unit question...

[brynden29]

I have searched all over and can not find an answer to my simple question. Where are the relays located for the A/C? My mechanic told me that there is a relay that is out because if they bridge past the relay the A/C blows cold air. Now I need to replace the relay. They told me that they would have to get into the dash to do it. Is that true? Any help would be greatly appreciated.

 

[brynden29]

They gave me a wiring diagram that showed the relay, but I don't have it. It is in the car and the car is still in the shop.

I guess I am really wanting to know if there are any A/C relays in the dash?

 

[S_Ranger]

Well have you checked the free-on? Get a gauge and check to L port which is under the intake manifold. If it reads ok then you can advance to the next step like checking the compressor which is under the master cylinder.

To check that just turn the ac on and listen for a click and the compressor in action. If that passes then keep moving up. I think all the relays in the fuse box are the same part number so try taking the headlight relay out and use that to temp. replace the ac one. It's a good way to test. LMK the update.

 

[Defiant]

Your mechanic doesn't have a shop manual?

 

[Raph]

If the low side has enough freon,check the compressor-- if you turn on the ac and the clutch doesnt engage,check the wires that connect to the compressor.. if theyre ok,chck the resistance of the compressor clutch.. should be 3 ish ohms .


The easiert way to check your compressor is to do the following(very dangerous..dont do this alone!)

1.Turn on your ignition, have a friend do this .

2. Hold a boxend wrench close to the compressor clutch (where the belt runs)

3.Have your friend turn on the ac switch and ventilator..the clutch will magnetize and pull the wrench out of your hands.. dont loose your fingers trying this..just hold it very very loosley. if the clutch magnetizes,the wrnch will stick to it and your compressor is fine.

 

[brynden29]

I forgot to add in my original post that I just replaced the compressor and everything else that goes with it (spent over $1200) about 2 months ago. The A/C worked fine, then it got cold here and I did not need it. I tried it last week and it did not work. I took it back to them and they checked the freon level and all the mechanical parts. All is fine. They said it was electrical and gave me a wiring diagram that showed where they thought the problem was.

I told them that if it was electrical that I could do it. They said they would need to get into the dash and that is where I told them to stop. I do not think there is anything in the dash that would need to be replaced. Is there?

 

[brynden29]

So here is the update. The schematic the mechanic gave me says that the 12V power to the A/C control unit is not getting there. Does anyone know where that 12V source comes from? Is it a relay? Or a fuse? Thanks.

 

[daves06r1]

Power has to come from one of the fuse or relay boxs under dash or under hood.

 

[Defiant]

The AC also has its own control unit, on the evaporator.

 

[brynden29]

Ok, so it is not the condenser fan relay. I replaced it and it still does not work. The counter guy mentioned that if the dual pressure switch is not working that would cut power to the A/C control unit. Can anyone tell me where the A/C dual pressure switch is located?

 

[Defiant]

On the receiver. But that's not it, it's probably the control unit on the evaporator.
When they did all this replacing, did they change over to 134a, or is it still a Freon system?

 

[MarkAngelo05]

Hey, Definitely check the A/C control unit. I had 2 blow out on my 2nd gen, its what makes the a/c system cycle on and off from the evaporator core temperature sensor. After I blew the 2nd one, I found out that my wiring had a short somewhere in the harness, Luv2Rally hooked me up with a wiring diagram and I saw that the Positive trigger went straight from the a/c control unit to the pressure sensor, and the condenser fan, then through the ecu, and the ecu triggers the compressor clutch(ecu cycles the clutch when you're above a certain RPM, it disengages the a/c compressor clutch). So what I ended up doing was just by passed the whole a/c control unit, and connect a wire straight from the Positive wire from the a/c switch, to the dual pressure sensor, then that way it still will function safely and shut off if need be.

Good luck! It's a PITA tracing all the wiring, but once you get it working, you'll love it!

I wish I had the diagram for you, but if you have the CD manual for the 1st gen, I'm sure it's in there. It'll make your life much easier.

Oh ya.. TELL THE SHOP your car has an A/C Control Unit. When mine was blown, I could by pass the relay and it turns on the fans and triggers the a/c switch, then the system gets cold...

Good luck!

Mark

 

[brynden29]

Hey, Definitely check the A/C control unit. I had 2 blow out on my 2nd gen, its what makes the a/c system cycle on and off from the evaporator core temperature sensor. After I blew the 2nd one, I found out that my wiring had a short somewhere in the harness, Luv2Rally hooked me up with a wiring diagram and I saw that the Positive trigger went straight from the a/c control unit to the pressure sensor, and the condenser fan, then through the ecu, and the ecu triggers the compressor clutch(ecu cycles the clutch when you're above a certain RPM, it disengages the a/c compressor clutch). So what I ended up doing was just by passed the whole a/c control unit, and connect a wire straight from the Positive wire from the a/c switch, to the dual pressure sensor, then that way it still will function safely and shut off if need be.

Good luck! It's a PITA tracing all the wiring, but once you get it working, you'll love it!

I wish I had the diagram for you, but if you have the CD manual for the 1st gen, I'm sure it's in there. It'll make your life much easier.

Oh ya.. TELL THE SHOP your car has an A/C Control Unit. When mine was blown, I could by pass the relay and it turns on the fans and triggers the a/c switch, then the system gets cold...

Good luck!

Mark

Thanks for the advice. Yesterday I pulled the A/C control unit and I noticed that there is one wire (green with a red stripe I think) that had power when I turned the A/C switch on. I then noticed that there is a Green with a White stripe wire coming out of the unit that did not have power. I jumpered across the two and *poof* A/C worked. So I am assuming it is the A/C control unit. I ordered a new one but it will take a few days to get here. Do you think it is ok to leave the two wires connected so my A/C works?

 

[brynden29]

On the receiver. But that's not it, it's probably the control unit on the evaporator.
When they did all this replacing, did they change over to 134a, or is it still a Freon system?

It was converted when I bought it. If the A/C control unit does not work I will check the evaporator control unit.

 

[MarkAngelo05]

Thanks for the advice. Yesterday I pulled the A/C control unit and I noticed that there is one wire (green with a red stripe I think) that had power when I turned the A/C switch on. I then noticed that there is a Green with a White stripe wire coming out of the unit that did not have power. I jumpered across the two and *poof* A/C worked. So I am assuming it is the A/C control unit. I ordered a new one but it will take a few days to get here. Do you think it is ok to leave the two wires connected so my A/C works?

Hey Bryden,

COOL! Good deal! Well, since I blew 2 a/c control units, I decided to try and just hot wire those wires together, but it did not work for me, since my problem was a SHORT somewhere in the harness from the cabin into the engine compartment. SO I ended up routing a wire directly from the cabin to the engine bay and followed the wiring diagram and bypassed the short.

Hard wiring it will be fine for now, but YOU gotta cycle your a/c on and off by your self.. The evaporator core freezes easily, and you'll here a LOUD WOOOOSH sound while barely any air is coming out of your A/C vents... That's my problem right now, so I just keep the Blower on HIGH and cycle it on and off once it gets REALLLLLY Cold...

Well, I'm glad you've solved your problem. How much was a new one?

Take care!

Mark

 

[brynden29]

Hey Bryden,

COOL! Good deal! Well, since I blew 2 a/c control units, I decided to try and just hot wire those wires together, but it did not work for me, since my problem was a SHORT somewhere in the harness from the cabin into the engine compartment. SO I ended up routing a wire directly from the cabin to the engine bay and followed the wiring diagram and bypassed the short.

Hard wiring it will be fine for now, but YOU gotta cycle your a/c on and off by your self.. The evaporator core freezes easily, and you'll here a LOUD WOOOOSH sound while barely any air is coming out of your A/C vents... That's my problem right now, so I just keep the Blower on HIGH and cycle it on and off once it gets REALLLLLY Cold...

Well, I'm glad you've solved your problem. How much was a new one?

Take care!

Mark

Wow, that is kind of scary. I will be getting the A/C control unit tomorrow so maybe I will just not use my A/C until then. I used it on the way home from work today and it was very cold. I hope I didn't mess anything up.

Edit: the new one from Satan is $63.00 or so, not too bad if that is the problem.