Cooling Fan / Air Conditioning [wiring?]

[Clay Nemitz]

Hey! I have a 1994 Volvo 850 Wagon (non-turbo) that I've had for about a year and a half. This site has been immensely helpful with various things for my car. I am having a problem with my air conditioning, as well as my cooling fan I think. I fear this may be a long post, but I mean to be thorough about what I know.

The problem:
My A/C had not blowing very cold due to low refrigerant pressure, so I decided to recharge it. Just to make sure everything was good, I replaced various o-rings as well as the accumulator. I hooked everything back together, vacuumed it out, and tried to charge it with a can of R-134. Refrigerant would not flow into the system and the compressor did not engage, so I unplugged the low pressure switch and jumped the connector, but the compressor did not engage. Last summer I jumped that connector which engaged the compressor which allowed refrigerant to go into the system (though I messed something up and was only able to get it up to ~20psi, thus my need to recharge it now). (As a side note, last year when recharging it, I shimmed the compressor clutch with a few guitar picks with help from things on here). I tested that connector and I did not have any power there. From what I read, if I don't have power at that connector, either my A/C relay is bad, or the wiring between the relay and the pressure switch is bad. I also read that my A/C relay might not work if there is a problem with my cooling fan switch. Recently it seems that my cooling fan has not been coming on, so I thought I would try to fix that (I replaced my cooling fan, fusible link, and relay last summer which got it working then). The fusible link from the starter to the relay is fine, and I have power from that at the relay. If I unplug the thing in the middle with the yellow and yellow/white wires and connect power to either plug on the relay, my fan comes on with either high or low speed, as it should. If I test either of the wires that go to the middle of the relay, I don't get any power. But I don't know for certain if there should be power there, because I would think that there would be only if the fan needed to be on, and I'm not positive if my car is warm enough to cause it to come on. To make the fan come on, I tried turning my A/C on and checking if I have power there (or if my fan comes on with it plugged in), and there is not. But my A/C is not working at the moment, so I don't know if my fan will come on if my compressor is not engaging. And thus I feel like I am starting to go in a circle to figure out what is wrong with the A/C and cooling fan.

Various info that may be relevant:
My A/C had been working, albeit not very coldly, prior to me messing with things. In trying to troubleshoot things I connected power to the A/C compressor clutch and it clicked, which apparently means it is fine. Another thing to note is that since attempting to service my A/C [and encountering these problems], my engine seems to be running a bit strangely. Prior to messing with things, my engine ran fine and idled smoothly. Since messing with things, it idles somewhat roughly. The tachometer stays right where it did before, but it sounds rougher. It runs like this when the car is idling in park, drive, or reverse, but when in neutral it runs smoothly and normally. Also, my temperature gauge occasionally ceases to work. It usually works (and when it does it stays right around 3:00), but sometimes it just drops as if the car were shut off.

Since I've found myself in somewhat of a circle going between my A/C and cooling fan as I mentioned above, I don't know where to start or what to ask. My thoughts are: how do I test whether or not my cooling fan is or is not working properly? Should I have power to the middle connector of the fan relay, or rather, when should I? Would my cooling fan not working properly indeed cause my A/C relay to not work properly, and thus my A/C pressure switch might lack power?

Any thoughts or comments are welcome. I thank you for your help in advance.

Clay

[Ozark Lee]

Welcome to MVS,

The fan will not come on until the A/C system reaches normal operating pressures. One can of R-134A will not get you there but it will get you close. About half way through the second can the fan should start to operate correctly.

As far as tracing the electrical stuff down you need to download the factory service manual which is hosted here.

https://www.matthewsvolvosite.com/downlo ... vo_850.zip

Once you unzip it see the file named System Wiring Diagrams.pdf. There are differences between the electronic and manual systems as well as between turbo and n/a engines.

We have some other, more detailed, schematics but they are a real bear to use since you need to keep flipping back and forth to the decoder ring to figure out what the component is.

...Lee