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heater fan inop 900 1993

Hi, I'm new to the sight. Hoping someone can assist me in trying to get my heating & ac fan to work. Hot here in SC this time of year>

Anyone know anything about problems along this line or have access to a good schematic? My '93 940 wagon's interior fan fails to function - working fine one minute - dead the next. Fuse (#16)is good, fan is good (12vdc directly to fan input & fan runs fine, switch is good (sane thing, 12vdc to switch input & fan runs fine and is speed controlled by the different positions).

The fuse list by the box also lists fuse #6 as being for the fan but I think this is only used on cars with automatic climate control - there are no connections to this fuse on the back of the fuse block. Fuse is good at any rate.

I thought it must be a relay but Volvo says no relay for the fan exists in this model. Tried tracing the wire (looks to be about 12 ga solid black both at the fuse and at the switch. Somewhere between these two points things get interrupted.

I have a Haynes manual & the schematic sucks - no real info. Help!!!








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heater fan inop 900 1993

First check the ground located on the right side.

I am looking at a 1993 Volvo wiring diagram. No relay. The resistor pack looks as if there is a fuse symbol with a diagonal line drawn through it. I have never seen this symbol and would think it is self resetting.

The following discusses a 740 but may apply to the 1993 940

FROM the 700/900FAQ
I believe a 92 has this feature but it might not have occurred until 93, anyway, the resistor may have a temp fuse integrated into it that will go open if the blower resistor has debris around it or if the blower motor drags. Either of these two will make the resistor get hot enough to trip the temp fuse. If the resistor has the temp fuse it will be a green ceramic covered resistor and the temp fuse will be adjacent to ceramic core. It is a silver 3/16" cylinder with tapered ends , one of which is white. In either case i can tell you w/o too much doubt that you will have to go behind glove box as the relay is there and the resistor is stuck into the blower case in that area also.

The MCC fan operation is independent of the heater and the A/C and shouldn't be too hard tracing the circuit. The fuse is #16 and you are correct about the black wire to the switch having 12V. Output side, look for 12V, fan position 1 on a yellow-blue wire going from the fan switch to the resistor pack.

Tom








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heater fan inop 900 1993

Thanks, but I don't think there is anything wrong with the resistor as everything fan related works perfectly if I put 12 vdc into the switch. The switch controls the speeds which go through the resistor pack and then to the fan so I know everything is ok downstream of the switch.

The problem is that no voltage reaches the switch though it is present at the fuse. I have run a temporary wire from the output of the fuse to the switch and the fan is now running normally. However, now my ac compressor does not engage.

There is something else going on between the fuse and switch. I've tried to trace the wire - it heads through the big bundle behind the fuse panel and looks like behind the dash. I've had the dash out (took that opportunity to re-flow all the solder joints on the dash panel and, wonder of wonders, I now have a fuel gauge - thanks to other posters for that advice)but can not locate the black wire behind it. took all the below dash stuff out - still no luck though it is difficult to get to everything down there.

I did notice that the ac on/off switch is not electrical. It instead controls a vacuum line. I put voltage to my compressor clutch and it operates normally.

Somewhere in there is something where these functions come together and its bad. Oh, for a schematic that actually shows this part of the electrical/vacuum circuit. Not in Haynes or Chilton. A counter person at the auto parts store recommended that I buy a CD from them that gives me access to info on a car of my choosing online at a site called "TotalParts" (I think that was it) Costs almost 30 bucks but you supposedly get access to better manuals and schematics. Has anyone had any experience withg a service like this?








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heater fan inop 900 1993

From fuse 16, there is a single wire going to a connector, C19, located to the left of the MCC A/C controller. After this connector is a branching point, a single wire splitting to two wires. This split may be on the output side of the connector, C19, but I am not sure. This split feeds two black wires, one going to the fan switch and the second, the A/C controller. Does the AC work? If so you are nearing the open circuit.

If there is no AC, you may have to pull the fuse/relay tray out and start tracing the open circuit from the load side of the fuse. Only one black wire exits fuse 16. The photo is from a '95 turbo.

Tom









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NMI 900 1993








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NMI 900 1993









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heater fan inop 900 1993

The only thing I can think of as a problem spot is a resistor pack, which I have on my 740, but I don't know about the 900's.

Other than that, the connections could be flakey. Honestly, I'd start smacking connection points when it's not working and see if it helps.

At the worst, you can kill an ant with a cannot and run new wire for the whole fan system. You may never find the circuit fault. It's the only way I ever got my driver's side taillights working.

Good Luck
William
--
1990 740 Turbo, on its way to stock specs, maybe beyond








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heater fan inop 900 1993

Yeah, that's kind of where I'm at too. Mine does have the resistor pack but it runs fine if I connect the output side of the fuse directly to the fan switch so I assume its fine. Guess I'll just route a new wire. I just wanted to make sure there was not some other something that was keeping it from working.








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heater fan inop 900 1993

I cut the black wire at the black 2-wire connector on the switch, fed the switch with 12volt from an additional wire attached to fuse 16. Now the ac compressor doesn't engage. If I would disconnect the original fuse 16 output and feed the AC circuit by connecting 12 volt to the wire I cut at the switch, do you think that would allow the ac to engage?
Marlin








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heater fan inop 900 1993

My '93 is doing the same thing today. I'm getting about 2.5v at the black wire in the black 2-wire connector at the fan switch. Does your ac compressor engage? Mine engages, but cycles every 10sec. and doesn't cool as much as it should. Were you successful at running another feed wire from the output of fuse 16 to the switch? If I run a similar wire, should I connect it to the black wire at the switch? Thanks.
Marlin








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heater fan inop 900 1993

Marlin

See my post to your message about this.







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