850 Heat Fan, High Speed Only

clay roby · Post by **clay roby** » 06 May 2006, 10:23

I have a '96 850 and heater/ac 4 speed fan only works on the high speed. I changed out the fan resistor network (no fun !) but the fan still only runs on high speed. I checked the fused and it seems unlikely that it's the switch. Anyone else seen this problem and have a suggestion what I should check next?

vibbase · Post by **vibbase** » 06 May 2006, 15:12

Yes, I have the same problem..........

However, when I dim the panel lights, the fan goes back to normal operation and the backlights of the control unit itself are not working. Hmmmm

I have replaced the power supply unit located in the air box (it had a short) This stopped the fan from running all the time but I'm now in the panel light conundrum. I plan on taking the car to a Volvo guy for some additional diagnostics. By the way, I get the 18 flashes thing on the control unit from time to time and also I have removed and inspected the cabin sensors. (both working fine)

I have posted my issues on this board and on Volvospeed with very little luck. It's a odd issue I hope to resolve soon.

pigpete · Post by **pigpete** » 02 Jun 2006, 09:14

let me know I have the same problem and have tryed so many things. Thanks

Post by **mom** » 02 Jun 2006, 09:42

Have a look at this, maybe it could help.
https://www.matthewsvolvosite.com/chat/p ... ght=#22359

pigpete · Post by **pigpete** » 03 Jun 2006, 19:16

I have disconnected all relays etc. Bought all new parts from scrap yard and still have the fanl running on full speed. Even changed the auto control unit.(hmi)

Going to pull the dash apart and look for fused wires in the wiring loom now!

procare · Post by **procare** » 03 Jun 2006, 20:40

Hi, you should check fan swhich. See if it works properly.
Good luck.

pigpete · Post by **pigpete** » 04 Jun 2006, 12:26

I changed the whole switch unit with spare one no luck thanks though.

Post by **MadeInJapan** » 04 Jun 2006, 15:03

Did you check the preostat (spell?) under the glove box with the knee bolster off? There is a "swich" like connection in there that can go bad near the fan itself...I seem to recall it has to do with the lower fan speed.

pigpete · Post by **pigpete** » 05 Jun 2006, 07:12

I will try this.Im unsure which "switch like " connection you mean as there are alot of wire around there. I have the knee bolster out and see lots of connecters etc. i will try thanks.