94 850 turbo wagon- new blower/power stage- quit working

Turbolena · Post by **Turbolena** » 24 Nov 2014, 10:14

I have read and re-read numerous threads and topic on blower motor and power stage trouble shooting. So I decided to replace power stage and blower together. Did the replacement and then connected battery and tested on acc power- fan adjusted with controller and turned off with car this seemed like success.
Later, after putting it all back together and I start the car and I get nothing! Just the 20 seconds of blinking on the ecc.
Fuse is not blown- but there is no power at the fuse box (no sparks when I replace the fuse).

The original problem was that the fan was stuck on high (well actually some mid range position at first, but then later stuck itself on high) and that it didn't turn off or adjust with the ecc control and the blower didn't turn off with the car.

What happened??? Do I need to replace the ECC unit. Did I fry the new power stage ??

Post by **Ozark Lee** » 24 Nov 2014, 22:50

You likely didn't cook the new power stage (blower resistor).

Did you check both fuses? Fuse 5 is the fuse that powers the blower motor.

Since you have a '94 it is very easy to read the diagnostic codes from the OBD-I port under the hood. The ECC codes are read from port B-1. If you don't have it you should download the factory service manual and then, after you unzip it, see the file named ac heater system auto.pdf. It will give you the troubleshooting procedures for any codes you pull. The link is here:

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

You may have numerous old codes that were from your original failure so I would suggest that you read and record all of the codes and then erase them. Any code that crops back up will be a current code.

...Lee

Post by **BEJinFbk** » 25 Nov 2014, 01:30

And check for power with a meter, not by looking for sparks.
That's in no way a conclusive method to determine if there's voltage.

Turbolena · Post by **Turbolena** » 25 Nov 2014, 21:11

Alright checked the B1 port codes: Reset them and got the 3 same codes.
They are as follow
4-1-1, 4-14-, 4-1-8. - 1st- siezed fan or excessive current, 2nd- Driver’s side interior temperature sensor inlet fan seized , 3rd- No control signal to blower fan power stage-

Would a broken wire on the big connector of the power stage cause such a failure? I would think that the excessive current would have been an old code but it came back. It has been cold here and I have not had a heated garage to get back into the dash board. Wondering if I should try a replacement ECC unit for the dash?

Post by **Ozark Lee** » 26 Nov 2014, 00:19

Try installing a jumper wire between the blue wire and the black wire on the large connector from the power stage. The fan should run full speed and there shouldn't be any "bad" noises from it.

...Lee

Post by **BEJinFbk** » 26 Nov 2014, 08:29

Turbolena wrote:Alright checked the B1 port codes: Reset them and got the 3 same codes.
They are as follow
4-1-1, 4-14-, 4-1-8. - 1st- siezed fan or excessive current, 2nd- Driver’s side interior temperature sensor inlet fan seized , 3rd- No control signal to blower fan power stage-

Would a broken wire on the big connector of the power stage cause such a failure? I would think that the excessive current would have been an old code but it came back. It has been cold here and I have not had a heated garage to get back into the dash board. Wondering if I should try a replacement ECC unit for the dash?

Sometimes an overheated connector at the fan motor
can cause excessive current draw. The contact can get
hot, loosen up and just not make a good connection.
Does the metal part of the connector appear discolored
or is there any sign of heat in the plastic or wire insulation?