1998 S90 blower replace when replacing blower resistor?

jefflamonica · Post by **jefflamonica** » 11 Mar 2016, 14:05

I've seen differing opinions on whether to replace the blower motor when replacing a failed blower resistor. Some have said a failing motor could take down the resistor, and I don't want to kill the new part. Any help is appreciated.

lummert · Post by **lummert** » 11 Mar 2016, 20:36

Seeing how easy it is the replace the blower motor I'd leave it for later.
A note: the blower motor is GM and is the same as used on many GM cars. I installed a blower motor from a 90's Cavalier/Sunfire in my 1988 760 Turbo Wagon.

93Regina · Post by **93Regina** » 11 Mar 2016, 22:30

jefflamonica wrote:differing opinions on whether to replace the blower motor when replacing a failed blower resistor. ...

Just pull fan-motor, and examine...bearings shot...no brainer...replace.

jefflamonica · Post by **jefflamonica** » 22 Mar 2016, 11:54

Finally got around to this this past weekend. Motor okay. Installed used replacement blower resistor acquired by previous owner. Fan blows constantly while key on, as with last resistor. Do I have another bad one? This is an MCC climate control system. Fan switch has no effect on the blower. Questions:

- Is it possible to test the resistor to see if it's good? If so, how would I accomplish that with my little digital multimeter?
- How do I eliminate the possibility that my climate control unit (switches, etc. in the center of the dash) is malfunctioning?

Really hope to resolve this, as AC season in the South is rapidly approaching. Speaking of which, compressor does not seem to be engaging.
- Insufficient charge and a low-pressure switch is preventing the compressor clutch from engaging?
- AC compressor relay bad?

Thanks for your help!
Jeff

93Regina · Post by **93Regina** » 23 Mar 2016, 08:15

jefflamonica wrote:MCC climate control system

Download and save this Q&A

I know little of ECC/MCC...I'll poke around later today

lummert · Post by **lummert** » 23 Mar 2016, 13:01

Should be able to check the resistor circuits using a DOM after reading up on the ECC wiring diagrams. Greenbook should have the best wiring diagrams.

93Regina · Post by **93Regina** » 23 Mar 2016, 13:21

jefflamonica wrote:MCC climate control system.

Here's Volvo's tech info

If your fan is running all the time, and if that schmatic on page 10 is the same as yours, then at Max Fan socket, either determine if pin-2 is hot all the time in all fan switch positions, and if not, replace the MAX Fan relay

jefflamonica · Post by **jefflamonica** » 23 Mar 2016, 14:08

Thanks for the input. I think our cars may be different. This appears to be an ECC system on an 850. When I was behind the glove box this weekend, I didn't see any resistors, like shown in your document. This diagram for a 97 960 looks more like mine, except shows ECC Control Module on the left side of the diagram (instead of MCC?). https://docs.google.com/folderview?id=0 ... xZDRhZTVk.

93Regina · Post by **93Regina** » 23 Mar 2016, 15:12

jefflamonica wrote:ECC

Which system do you have? Resistor means in physical reality, resistor. MCC has them, but ECC does not.

Automatic Climate Control Problems? Try This!!

jefflamonica · Post by **jefflamonica** » 23 Mar 2016, 16:49

Mine is an MCC system. To describe, three knobs from left to right: 1.) fan speed, 2.) air flow direction control, 3.) temperature. Below that are, left to right, buttons for recirculate and AC compressor on/off (snowflake icon). In the 98 system, does the blower resistor unit in the plenum of the fan -- in addition to stepping the various fan voltages -- also perform the function of the Max Fan relay?

93Reg, I looked at that posting, but mine is a manual system. No codes flashing. But ultimately, I am trying to diagnose the blower resistor versus the control unit. May have to take the wiring diagrams, figure out what should be hot when, at the resistor. How do I know? The diagram I referenced above shows 3 of the four just coming from the control unit, not what's happening inside the unit. If I'm reading it correctly, black is definitely ground. Blue/Black appears to be ground to the fan motor. That leaves orange at the fan motor, which I assume is hot coming from the control unit at pin A2 (could this be the max fan relay output?). I've read there's a relay soldered to the board on of the control unit. At the blower resistor, the diagram shows violet (4B) and pink (6B) connecting to control unit pins A8 and A19, respectively. What do I look for where? Sorry to be a PITA.