13 replies to this topic

[Square]

1996 Volvo 850.
Blower motor is stuck on high. Switch doesn't change speed or turn it off. Blower goes off when I pull either the speed fuse (30A) or the 1-3 speed fuse (25A). (Or turn the car off)

_No_ lights on the control (Recirc/AC). I believe it may be the automatic AC version as the fan speed selector has an AUT option.

Should I replace the stage or is it likely something else?

[BEJinFBK]

If you have a 4 speed fan control, it's the basic manual system ( MCC ).

The MCC has a "Full Speed" (speed 4) relay that overides the speed control
resistors that give you speeds 1-3. You'll find it next to the blower, behind the
glove box. It's marked as # 2/24 in the diagrams. That relay gets energized by
putting the speed switch in position 4. If fuse 31 shuts it down, you probably
have a monkeyed up speed switch. Check for 12 volts at pin 86 on that relay.
If it doesn't drop off when you take the switch off of speed 4, get a new switch.

 96 850 MCC Diagrams.pdf   297.27K   2 downloads

 96 850 MCC Component Locations.pdf   419.4K   2 downloads

[Square]

Well, now I know for sure it's an ECC not a MCC.

This car is North America OBDII - no diagnostic unit. (Not that I could get a code with the REC and A/C lights not working.)

Seems most other users with a blower problem have a functioning ECC. There is only fuse 5 and 31 before the ECC, right?

[BEJinFBK]

Just to be sure - Which one of these:

 850 MCC panel.jpg   110.62K   12 downloads
Does the fan control have 4 speeds?

 850ECC panel.jpg   146.21K   14 downloads
Or is it continuously variable, with a setting marked "AUTO"?

[smokin' T5M]

My suggestion is change the power stage first. ECC doesn't usually fail in that manner. Power Stage is what regulates variable speeds. "5" (top speed) is 12V from the battery.

[maple017]

I got the same problem last summer... blower stocked on high speed... I had to remove fuse of turn off the car to get the fan off...
Just change the power stage/blower resistor and you will be fine ! If you need one for cheap, PM me, but I'm in Canada...
It is the one for the ECC : http://www.fcpgroton...limate control)

easy to change... under the glove box !

[BEJinFBK]

Square, on 19 January 2012 - 12:48 AM, said:

1996 Volvo 850.
Blower motor is stuck on high. Switch doesn't change speed or turn it off. Blower goes off when I pull either the speed fuse (30A) or the 1-3 speed fuse (25A). (Or turn the car off)

_No_ lights on the control (Recirc/AC). I believe it may be the automatic AC version as the fan speed selector has an AUT option.

Should I replace the stage or is it likely something else?

It can't have both.
If it's ECC, you probably do need a new power stage.

[Square]

It's ECC. I'm pretty handy with the soldier so I'll try replacing the with a STW80NE06-10 (A bit closer match than the STP140NG55 to the original 2SK1423)

[BEJinFBK]

Good luck with that. Hopefully, it'll save you some cash.
But the stages usually go because the motor kills it.
Check that out, too.

[maple017]

BEJinFBK, on 19 January 2012 - 11:50 PM, said:

Good luck with that. Hopefully, it'll save you some cash.
But the stages usually go because the motor kills it.
Check that out, too.

True, mine was loose on the blower motor bearing and it was doing some noise... changed both and it's now good !

[DVolvoguy850T5]

If your fan makes noise and you have ECC, get a new fan motor. +1 to the other comments. Your bad fan motor will kill your power stage. You can get after market parts on eBay for 63 bucks. Just installed a fan and power stage on my ride.

Also, I read a thread at Matthews Volvo site about overhauling an ECC power stage. It may not work. There is also a thread about the MCC resistor/speed control and the diode in it can be replaced rather easily.

[BEJinFBK]

FWIW, it's not a diode.
It's a thermal fuse.

[DVolvoguy850T5]

http://volvospeed.co...-guide-850sv70/

You are correct and my bad... Thermal Fuse... FWIW means what?

[BEJinFBK]

For What It's Worth.

( And , FWIW, I used to know the value of
that fuse, but I have dun fergot... )