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940 Climate Control Unit problems

N

niquemarshall

New member
Joined
Sep 20, 2012
Location
Ohio State Univ
As title states, I've got a 940 with mcc problems. I realized this when I did not get 12v at the pressure switch but the compressor engages when 12v is applied directly to it. I took it out, and spotted what appeared to be very very small dark circles. They didnt look like they would cause a problem but I touched them up anyway. I have 3 different units and none of them are able to give me 12v at the switch. I dont see how all three of them have bad relays. I even looked up the Takamisawa relay and I cannot get it anywhere not even Ebay. Is there another part that can cause the ac circuit to not engage? I have 2 with AC OFF button and 1 with the snowflake icon. I'm assuming the ac is supposed to engage when the button is pressed? Or does it engage with the button is unpressed?
 
I have fiddle with these with no success. As you know they loose the a/c circuit. Maybe a member has the answer. It was a lot easier to add a switch for compressor control. The green wire is the compressor .
 
You must have minimum pressure in your accumulator (low side pressure leaving the evaporator). For a test, jumper the low press. switch leads with a paper clip. If this gets your 12V at the green wire, success is yours.

If NOT report back.
 
DET17 said:
You must have minimum pressure in your accumulator (low side pressure leaving the evaporator). For a test, jumper the low press. switch leads with a paper clip. If this gets your 12V at the green wire, success is yours.

If NOT report back.
Click to expand...
As far as I know, I'm not getting any voltage at the pressure switch. The only way to activate the compressor is to apply 12v directly to it. Also there is no pressure in the ac system but that's a whole new problem; I'm trying to solve the electrical portion first. Afterward I'll replace my ac lines and condenser
 
Years vary the equipment; I don't know what year/model you have.

So far as trouble shooting your control side failure, you must have the schematic for your year/model. Some 7/9s have a relay behind the glove box; later don't have this relay, just the main one in the fuse block. Is your fuse good to the AC system?
 
DET17 said:
Years vary the equipment; I don't know what year/model you have.

So far as trouble shooting your control side failure, you must have the schematic for your year/model. Some 7/9s have a relay behind the glove box; later don't have this relay, just the main one in the fuse block. Is your fuse good to the AC system?
Click to expand...

I'm not sure where this ac fuse is located on a 93 940 wagon. As far as the relay goes, I've seen that the only relay is the one integral to the CCU
 
From memory, the 92+ has no relay behind the glove box.... I think perhaps 91 only. Fuse is in your main fuse area right behind the ashtray.

Do you have the manual for your 93? It will show you..... or try Google images. Should be 15A I think for the AC
 
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DET17 said:
From memory, the 92+ has no relay behind the glove box. Fuse is in your main fuse area right behind the ashtray. There is a relay also in the white block which contains fuses and the primary AC relay is there as well.

Do you have the manual for your 93? It will show you..... or try Google images. Should be 15A I think for the AC
Click to expand...
I used to, but someone broke into my car once and stole it
 
Correction! Pulled my PDF this morning to show the actual schematic for AC control..... and there is no relay.

Either MCC or ECC (figure out which your 93 has, go to the 700/900 Maint. Pages courtesy of Volvo Club UK).... the rest simply HI press. switch in series with LOW press. switch, then the compressor. There are different fuses listed dependent upon the type of controller; will be listed on your fuse cover pullout.
 
DET17 said:
Correction! Pulled my PDF this morning to show the actual schematic for AC control..... and there is no relay.

Either MCC or ECC (figure out which your 93 has, go to the 700/900 Maint. Pages courtesy of Volvo Club UK).... the rest simply HI press. switch in series with LOW press. switch, then the compressor. There are different fuses listed dependent upon the type of controller; will be listed on your fuse cover pullout.
Click to expand...
Took a look at the fuses, number 6 and 16 looked fine. Will take a look at the schematics although they can be a bit overwhelming haha. Any way what component rests between the ccu and the low pres switch?
 
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I just shot the second pin on low pressure harness all the way to the compressor and I've got continuity. Gonna pull the mcc and check continuity from pin 10 to ground. Will check back
 
Once you confirm your schematic, find the power supply to your MCC. If you've got 12V there, and nothing being outbound to your AC clutch, use a larger paper clip or jumper wire, and bypass both LOW and HIGH press. switches. The AC output I believe is delayed by the ECU for startup, so don't just key the ignition on..... you may continue to get nothing.

READ the 700/900 Volvo Club UK maint. pages I continually refer to.... better explanations there than you will ever find on TB.
 
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