HELP!! A/C compressor!

[RichardLSU]

When I purchased my car the PO went on and on about how he spent all this money upgrading the A/C system in the car. I have all receipts to prove this. However, the compressor was getting no power. My tach wasn't working originally either. Over time the tach began to work and still does. I'm still not getting any power to the compressor though. From what I understand there is a series of sensors that control them both. I thought though that if one goes out they all went out (kinda like xmas lights). But now that the tach is working shouldn't the a/c compressor be getting power too? I'm perplexed and don't know where to begin. Any thoughts or tips would be greatly appreciated. Thank you.

[pimpernell]

Originally Posted by RichardLSU

When I purchased my car the PO went on and on about how he spent all this money upgrading the A/C system in the car. I have all receipts to prove this. However, the compressor was getting no power. My tach wasn't working originally either. Over time the tach began to work and still does. I'm still not getting any power to the compressor though. From what I understand there is a series of sensors that control them both. I thought though that if one goes out they all went out (kinda like xmas lights). But now that the tach is working shouldn't the a/c compressor be getting power too? I'm perplexed and don't know where to begin. Any thoughts or tips would be greatly appreciated. Thank you.

Don't know what kind of work was done to your car, but I would first check any fuses that are associated with the AC. The other thing is that if the AC system is low on gas, the clutch on the compressor will not power up. There is a pressure switch that will not allow the clutch to engage if the AC charge is not up to snuff. If your AC charge is low, and if the compressor is activated, you can burn it out.

[RichardLSU]

Well, I'd imagine that its fully charged. To him, it seemed like a major selling point on the car so it was severely stressed. How would I check to see if it was charged?

[tobybul]

Originally Posted by RichardLSU

Well, I'd imagine that its fully charged. To him, it seemed like a major selling point on the car so it was severely stressed. How would I check to see if it was charged?

IIRC, I jumped the pressre sw terminals to chk if the comp works.

[mdisav]

check overvoltage protection relay on 85's and up. Drop passenger panel under dash and look right just above the kick panel. There should be a silver relay with a red top and a 10A fuse. See if it is blown. This usually affects the tach too. If it is not blown make sure the fuse is getting a good connection.

[OlBrenner]

Originally Posted by tobybul

IIRC, I jumped the pressre sw terminals to chk if the comp works.

I concur... take the the two spade style connections on top of the dryer connected to the pressure switch and with the car running tap them together, the compressor clutch should engage. Then you are either low on freon or the pressure switch is bad, probably low on freon which means you have a leak... time to take it to an a/c mechanic if you don't have the knowledge to fix it.

[Scott98]

Originally Posted by OlBrenner

I concur... take the the two spade style connections on top of the dryer connected to the pressure switch and with the car running tap them together, the compressor clutch should engage. Then you are either low on freon or the pressure switch is bad, probably low on freon which means you have a leak... time to take it to an a/c mechanic if you don't have the knowledge to fix it.

+1. That switch activates the compressor clutch. You need to start there.

Scott

[jbach36]

Originally Posted by pimpernell

Don't know what kind of work was done to your car, but I would first check any fuses that are associated with the AC. The other thing is that if the AC system is low on gas, the clutch on the compressor will not power up. There is a pressure switch that will not allow the clutch to engage if the AC charge is not up to snuff. If your AC charge is low, and if the compressor is activated, you can burn it out.

I have no idea if it's the fuses, but even if your fuses look good, replace them ALL with the new, copper type. The old metal type become pitted, and can build up resistance, creating excess heat on the electrical components, then short stuff out. I might have my terminology wrong, but the bottom line, change 'em all.

jeff

[mdisav]

If the overvoltage protection relay fuse is blown you will not be able to jump the pressure switch. This is only on 85 and up.

[hangit]

Originally Posted by tobybul

IIRC,

What does this mean? Thanks.

John

[OlBrenner]

Originally Posted by mdisav

If the overvoltage protection relay fuse is blown you will not be able to jump the pressure switch. This is only on 85 and up.

True, but start with the easiest and work back. Check fuses first then jump the wires at the pressure switch, if the compressor doesn't engage then check voltage at one of the wires, one should have 12v when the climate control is on min and NOT on EC. If you're not getting 12v at the pressure switch then work your way back to the relays, no switching voltage at relays then go further back to the climate control panel. Tis the beauty of very basic electrical circuits, get a diagram (http://pauldrayton.com/uploadfiles/merc/Service/W123/Index/Groups/83ClimateControlSystem.html) and methodically work your way through it until you find the fault. Similar to tracking down vacuum leaks but a bit easier if you ask me...

Oh yeah, IIRC stand for "if i recall correctly".

[mdisav]

Also there is a Klima behind the blue flying saucer. Pull the black top off and jump KL and 87 to engage the clutch. Both the klima and over voltage protection relay on 85's must be working properly to give continuity to the pressure switch on the receiver drier.

[rrgrassi]

Originally Posted by hangit

What does this mean? Thanks.

John

If I Remember Correctly...IIRC