94 850 Turbo. Been reading up on thread but still not able to figure out what is wrong. Both buttons light up on starting car. Blower motor does not blow air at all. No hot or cold. Pulled the blower motor and it's fine. Switched out the blower motor resistor and still not working. Any ideas?

 

Buttons light up or buttons flash? Buttons flash because there is a self diagnostic code/s stored in the climate computer. Common is the fan motor uses too much current to start up, the CCM will then store a code and turn the power off to the motor. Check the self diagnostic codes in the CCM.
If the over-current code is stored - even though the motor works - the solution is to replace the motor.

A work around - sometimes this works. Start with the Climate system off when starting the car. Then slide the fan switch over to a lower speed to turn the system on. .

 

When you mean the fan motor, you are talking about the blower motor? Also, I do see a port front of the shift lever that looks like an OBD port, should a reader tell me what the codes are?

 

DefaultWhen you mean the fan motor, you are talking about the blower motor? Also, I do see a port front of the shift lever that looks like an OBD port, should a reader tell me what the codes are?

 

Yes the fan motor for the heat/ac system. There's a self diagnostic box under the hood that will talk to various systems. This page gives info


https://www.matthewsvolvosite.com/read-codes-volvo-850/

Looks like Climate is terminal #1 in the b (grey) diagnostic box and 411 code is fan overcurrent.

 

Unfortunately I do not see a box under the hood to plug the OBD Scan tool into. Only the one by the shifter and it does not show any codes present.

 

It's not a normal OBD port, that's in the console and PRE 1996 cars does very little. It looks like this, plug the loose wire into the port you want, push the button in a specific fashion and the light blinks codes. or use the old volvo scan tool. What year is your car?

 

Found. Thanks! I was looking for something different. Got a chet load of codes

 

Codes 417, 418, 419 relates to the blower motor but not sure where it tells me to look. Gonna Google on.

 

Nothing yet but power is going to the blower. Might be a ground possibly? Also if the ECC unit has to be replaced I see that it must be brand new and not a used one as it's programmed to the car?

 

maybe a bad fan resistor (power stage) The right temp sensing fan won't turn off the heater fan.

417 Passenger’s side interior temperature inlet fan seized
418 No control signal to blower fan power stage
419 Faulty diagnostic signal from blower fan power stage

The resistor varies the ground , there's + 12v to the fan all the time. The CCM is not coded to the car, a used one should be plug and play. However the CCM in 99 + cars are tied to the VIN and require a download to make a new one work or possibly a used one from the same year and part number might work.

 

I had replaced the blower motor resistor but the blower fan still wont run.

 

How about your code

"418 No control signal to blower fan power stage"

Is there a control signal to the power stage? If not you may have a bad connection or bad climate module.

 

It was a bad AC control module. Installed used one and seems to be working again. Thanks for the help!