1995 850t no blower code 418

[waybux]

Hello,

I need some assistance diagnosing this volvo I am working on.

Here is what I have: 95 volvo 850 with eec climate controls.

I have no blower function on any speed. I retrieve the codes and had a few for damper motor resistance but the main issue is the 418 blower motor signal.

The blower motor is wired for constant power and is good. I jumper a ground to the plug and blower takes off like a jet. Now according to mitchell on demand the signal wire from eec to power stage (brown/black I believe) is supposed to have min 6 volts and max of 8 volts when the fan is switched on. Mine only has 4.01 volts and doesnt increase or decrease regardless of fan on low,med,high.

I have swapped the power stage for a used from local junk yard, made no difference. I swapped 3 different eec, no difference.

I am at a stop. Any suggestions or assitance?

a little side note craziness: if I jumper B+ to signal wire doesnt work, however If I turn off key, jump b+ to signal wire then turn on key blower motor works on high speed. My logic is this means the power stage for a split second is receiving a jumper signal of approx 6-8 volts and closes ground circuit to blower. Thus the issues is the low voltage signal from eec to power stage. But can it be I have 3 p.o.s. eecs with low output signal??? Or is there something else controlling or limiting the eec signal??

[atucker1]

I doubt this is it, but worth it to double check. I had a similar problem and replaced the power stage since the motor tested good. When I put it all back together, it still didn't work. Turned out there were some wire connectors mounted ON the fan (didn't plug into the fan, just mounted on the case) that I had unplugged and not noticed since they just plugged into each other, not anything on the fan. That was it. The difference was when those were unplugged the whole ecc unit was dead, no codes, no lights, nothing.