posted by
someone claiming to be JaredB
on
Thu Aug 24 00:43 CST 2006 [ RELATED]
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'93 940 with MCC
Recently I had a failure of the blower motor resistor pack AND the wire from fuse 16 to the fan speed control switch. After fixing that, my compressor will no longer engage. I'm getting no voltage at the pressure switch. Possibly the temperature control is not work either.
Can someone confirm if the power wire off of fuse 16 feeds anything other than the blower switch?
And are there voltages I can check at the MCC?
If I don't fix this tonight I've got a 500mi+ trip with no A/C
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Dear JaredB,
May this find you well. According to a table on p. 21 of Volvo Tech Manual 3502201 (Lighting, Instrumentation, and Other Electrical Equipment - 700/900, 1982- ), Fuse 16 (30A) supplies:
(a) Heater fan standard heater
(b) Heater fan AC MCC
(c) Electronic AC ECC
The terms used in (a)-(c) are exactly as printed in this manual.
In short, this circuit is dedicated solely to climate control.
According to the 93 940 wiring diagram (Volvo Tech Manual 32208/1), p. 156, a black wire runs from the ignition, to Fuse 16, and then to the climate control module. That is mounted above the radio, in the front center console.
The black wire branches: one leg runs to the fan selector switch on the climate control unit, and the other leg runs to the main connector, on the climate control unit.
I'd guess that the blower motor is failing/has failed. It could be drawing more power than it should, overloading the fuse, and causing it to "blow". Has the blower motor made any noise, other than its normal "whirring" sound (low pitch, smooth and even)?
Hope this helps.
Yours faithfully,
spook
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posted by
someone claiming to be JaredB
on
Thu Aug 24 02:41 CST 2006 [ RELATED]
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Thanks! that mostly answers my question.
Does the wiring diagram show which connection on the CCU harness it goes to?
What I had found is that the power wire from fuse 16 to the fan selector switch would hold 12v until there was a draw. But if I ran a new wire from the same fuse (using one of the availabe 2 remaining connections), it would work. The fuse was not blowing.
So, if this wire also feeds the CCU then it also is probably experiencing the same problem, hence why my A/C doesn't work.
Does the wiring diagram show which connection on the CCU harness it goes to?
If I know which one it is, I should be able to test it, and try tapping in a new wire there as well.
Thanks again! You might have just saved my life this weekend
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Dear JaredB,
Good a.m. and may this find you well. The black wire, when it leaves Fuse 16 goes through Connector-19, after which it branches.
One leg goes to position 1, on the fan selector switch (when you look at the Climate Control Unit (CCU), from the back [with the knobs facing away from you], the black wire attaches to the left-hand small connector, below a Red/White wire).
The other leg goes straight to position 12, on the CCU's main connector (which has 14 pins). The even-numbered pins are on the lower row. Pin No. 12, is second from the left, as you look at the back of the CCU, i.e., with the knobs facing away from you.
I suspect the relay, inside the CCU, has somehow shorted. Unfortunately, these relays are not available as a spare part.
Hope this helps you to keep your cool!
Yours faithfully,
spook
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posted by
someone claiming to be JaredB
on
Thu Aug 24 06:13 CST 2006 [ RELATED]
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Thanks, that's what I needed. I'll check it all tonight
I have already started looking into getting a rebuilt MCC if patching a new wire doesn't work.
If you have reccomendations as to where to get one if that ends up being the case, let me know.
Thanks
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Dear JaredB,
Good p.m. The first thing to try, in regard to the MCC CCU, is to re-flow the solder joints, where the relay is affixed to the circuit board, and where the main connector is attached to the circuit board.
These joints develop micro-cracks, some of which are too small to be seen with an unaided eye. Touching the tip of a soldering iron to each joint (for 1-2 secondfs), so that the solder liquefies, closes the crack and so restores power flow.
This requires removal of the unit, the circuit board cover (shiny metal, held by four small tabs) and four screws, so you can access the underside. The ribbon connector need not be detached.
Best of luck with this.
Yours faithfully,
spook
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posted by
someone claiming to be JaredB
on
Thu Aug 24 14:25 CST 2006 [ RELATED]
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I got lucky
I took it all apart again and was testing the wiring. And what do you know, it started working.
What I believe it was, was the single wire connector behind the glove box just next to the console (C19). Until someone on VS sent me a wiring diagram I did not realize it was part of the MCC electrical system. This connector had some black "tar" inside of it, and I think by re-seating it got a solid connection. After confirming everything kept working, I just cut the connector and soldiered the wires together. The wiring was fused to the sheath in places.
Anyway, it's all working. Nice to have an A/C and blower again. :)
Thanks for all the help!
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