I've been trying to fix a problem with the ECC fan in my '94 964 for a few months now. The problem started one misty day when I was driving the car and the fan just quit. I thought the fan had finally kicked the bucket (had been making a little squeek when it stopped). So, I put in a good fan out of an '88 765. That didn't work and that's when I realized the 30A fuse for the fan was blown (oops). So, I replaced the fuse and the everything was fine.....For about 2 minutes. Every time I put a new fuse in and turn the fan on, the fuse blows (with an noticeable snap) in about 2-5 seconds. I tried replacing the ECC control unit (dials) with one out of the same 765; Nothing changed. So, I looked up the wiring diagram (http://caunter.ca/volvo960/xg14802.pdf) and went from there. I looked next at the "ECC Power Unit" and surrounding wiring. I discovered a wire (pink/white) that had been repaired at some point and still had a bare spot, so I covered the bare spot with electrical tape; No luck. Next I tried disconnecting the fan from the ECC Power Unit; Still no luck. The fuse still blew with the fan turned on at the dial, but without the actual fan connected. Therefore I unplugged the ECC Power Unit; Then the fuse didn't blow. That brings me to today when I replaced the Power Unit with another out of a '93 965 (what a pain to replace!). I plugged in the new power unit and, after the fan being on for ~5 seconds.....POP goes the fuse. I felt like driving the car off a cliff!!! AGH! One thing I've noticed is that when the fan dial is at "0" and I install a new fuse, I get a spark at the fuse plug and the fan comes on briefly. I don't know why the fan would come on with the dial set to 0. Anyway, I am SO open to suggestions. I'd really not like to take it to a shop and spend a ton of money looking for this problem. In fact, I'm not even sure where I would take it as my mechanic has already looked at it once and I can't think of any other Volvo mechanics in the area who I think would be able to solve this problem. I don't think our local Volvo dealer would have much luck with it either as they mostly service newer Volvos. So, ANY HELP would be VERY MUCH appreciated!
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Chris. Halifax N.S. '98 V90 > 198K km, '94 964 > 90K mi. SOLD: '91 745T and '91 745 NA (I miss both of them!).

You might want to unplug the connector at the a/c low pressure sensor on the accumulator in the engine compartment and then replacing the blown fuse. By disconnecting this plug you have eliminated the compressor circuit load from the ecc power unit. If the wiring or compressor clutch is bad it would blow the 30 amp fuse #28 in the fuse panel. Let me know what happens when you disconnect this circuit. John
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"It's hell to get old!"

Hi John,

It worked! Today I finally got a chance to try disconnecting the A/C low pressure sensor. I pluged in a new 30A fuse and now the ECC fan seems to work great. Progress! Now, I just have to figure out what's wrong with the A/C. The yellow and black wire to the sensor has been cut and male and female connectors installed. I don't know why someone would do this, the wire appears fine otherwise and the connectors look to be in good shape.....
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Chris. Halifax N.S. '98 V90 > 198K km, '94 964 > 90K mi. SOLD: '91 745T and '91 745 NA (I miss both of them!).

I am glad you are on the way to figuring out what is wrong with your 960. You might want to disconnect the compressor clutch connector, reattach the low pressure sensor and then see if the fuse blows. My 940 clutch had a bare spot on the wire leading into the coil and blew the fuse. I was able to remove the clutch and coil and put some heat shrink tubing over the bare wire and the a/c has been working great for a few years now. Good luck! John
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"It's hell to get old!"

Ok John, that's the next thing I'll try. Thanks for the help!
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Chris. Halifax N.S. '98 V90 > 198K km, '94 964 > 90K mi. SOLD: '91 745T and '91 745 NA (I miss both of them!).

Thanks John, I'll try that.
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Chris. Halifax N.S. '98 V90 > 198K km, '94 964 > 90K mi. SOLD: '91 745T and '91 745 NA (I miss both of them!).

Bad ground (wire? wires?) behind the relay box.

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alex

Yeah, that's what I was kind of thinking since it didn't make any difference when I changed the ECC Power Unit which I thought was the problem. I'll have to try to follow the ground for this unit if I can.
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Chris. Halifax N.S. '98 V90 > 198K km, '94 964 > 90K mi. SOLD: '91 745T and '91 745 NA (I miss both of them!).

Dear CW,

May this find you well. When you use the term "fan", do you refer to:
(a) the blower, under the dashboard, that moves air inside the passenger cabin?
(b) the auxiliary cooling fan, in the engine bay, that comes on to help cool the engine, when the outside temperature is high?

Does the term "power unit" refer to:
(a) the ECC controller (located above the radio, in the front center console)?
(b) the blower motor (located under the dashboard, above the passenger's footwell [USA/Canada models])?
(c) the the auxiliary cooling fan (in the engine bay)?

Have you opened up the ECC and re-flowed the solder joints that:
(a) connect the relay (switch) to the circuit board?
(b) attach the main connector to the circuit board?
These joints develop micro-cracks over time, cracks usually too small to be seen with the unaided eye. Usually, these cracks will cause intermittent operation, or keep the system from working.

The fact that you refer to "repair work" - and found a partly un-insulated wire - suggests to me, that someone may have worked on the circuit board or wiring, and inadvertently damaged it. If you changed the ECC, and the problem persists, then the problem is likely to be in the wiring.

It may be necessary to trace each wire. Plainly there's a short circuit. A conductor is touching metal, either the body, or another wire.

I'd start at the area where the "repair" was done, and go from there.

Hope this helps.

Yours faithfully,

spook

Hi spook,

I am referring to the Electronic Climate Control (ECC) system and the operation of the ECC fan (blower fan for the interior). The fuse that blows is #28 "ECC, Air conditioning" (marked ECC fan in car) and it's a 30A fuse. The term power unit comes from the ECC wiring diagram (see the last page here: http://caunter.ca/volvo960/xg14802.pdf) refering to a component mounted on the top of the climate system air box just above and left (from inside) of the ECC blower fan. When the blower fan is disconnected from this unit the fuse will still blow, but when this unit is disconnected the fuse will not blow.

I have not opened the ECC control unit and re-flowed the solder joints. I can't see how this can be the problem though as I tried a totally different unit out of another car and nothing changed. When you refer to the "relay" and "main connector", are you talking about components which are inside the ECC control unit?

The only repair work that I found in this area is on the pink/white wire that runs from the ECC Power Unit to the Motronic (MFI) System Control Module. This wire had a break that had been repaired in the past and it's insulation was stripped in one area (which I covered with electrical tape). Other then that I have not noticed and wiring problems. I've checked the wires as close as I could without opening the loom.

I'm really not very experienced in tracing shorts, so I'm not quite sure where to start. This is why I was thinking about trying to find someone locally who is experienced in working with this ECC system.

Anyway, thanks for the help so far! I'd really like to get this fan (and therefore the A/C) working again!
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Chris. Halifax N.S. '98 V90 > 198K km, '94 964 > 90K mi. SOLD: '91 745T and '91 745 NA (I miss both of them!).

Do yourself a huge favor and buy the Volvo OEM wiring diagram book for this car, which will save you hours of headaches in tracing circuit faults. Your problem appears to be a short in this "power unit". Look there first.
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See the 700/900 FAQ under 'Select Link' button on the top right.

Hi Steve,

I may just have to do that. I was under the impression that the one I have been using from that website is pretty good. Will the book show me more? Yeah, I figured the short was in the power unit too, but the fuse still popped when I put another power unit in.....
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Chris. Halifax N.S. '98 V90 > 198K km, '94 964 > 90K mi. SOLD: '91 745T and '91 745 NA (I miss both of them!).