Blower Fan Stuck On - Burned Electrical Smell - 1993-850

Paul-93-850 · Post by **Paul-93-850** » 16 Feb 2010, 21:21

1993-850 non-turbo

Suddenly, my cabin blower fan is stuck full on. There was a click and it started blowing. There was a very strong burned electrical smell. The fan controls have no effect. Blowing stops when I turn off engine but it starts blowing again when I turn the key on. It happened tonight so I noticed the console lights for ac, air, etc are now out.

Post by **Ozark Lee** » 16 Feb 2010, 21:36

Your power stage (blower resistor) shorted out. In the short run all you can do is remove fuse number 5 to keep the blower from running your battery dead.

...Lee

Paul-93-850 · Post by **Paul-93-850** » 16 Feb 2010, 21:57

Ozark Lee wrote:Your power stage (blower resistor) shorted out. In the short run all you can do is remove fuse number 5 to keep the blower from running your battery dead.

...Lee

OK I'll remove the fuse, then what? Solder a new resistor?

Post by **Ozark Lee** » 16 Feb 2010, 22:05

On the ECC it is actually a MOSFET transistor, it really isn't a resistor at all. The bad news is that the original part is made of a rare substance called UNUBTANIUM - you can't source the original component. There is a thread on Brickboard where a guy scared up a new part from an internet supplier that seemed to be close enough to work.

Fortunately for me I have not yet had to replace mine so I don't know how well the brickboard fix works.

...Lee

Paul-93-850 · Post by **Paul-93-850** » 17 Feb 2010, 13:27

I saw the email joke about "unubtanium".
Seriously, this has to be a common enough problem that someone knows the options - new part, used part, fix part. At this point I don't even know how to remove and inspect the part. There was a strong burning smell so I worry that when this part failed that it could have burned out other parts. I removed the fuse so the fan doesn't blow, but my window could fog up dangerously.

Post by **Ozark Lee** » 17 Feb 2010, 14:59

How did the blower motor sound before the failure? Were you getting any squeaks from it (particularly on turns)? The usual scenario is that the blower bearings dry out and the blower motor itself starts to draw excessive current.

Buying a used power stage is a real crap shoot. Some are good and some are bad and there is no real good way to test them with an ohmmeter since the failures tend to be around 50/50 between a shorted out unit like yours or one that is open and the blower never runs.

You might want to try Darrell Waltrip Volvo for a new one if you decide to go that route, the have terrific pricing on OEM parts. (800) 689-0021 and ask for Jamie or Don.

...Lee

Paul-93-850 · Post by **Paul-93-850** » 17 Feb 2010, 15:37

Ozark Lee wrote:How did the blower motor sound before the failure? Were you getting any squeaks from it (particularly on turns)? The usual scenario is that the blower bearings dry out and the blower motor itself starts to draw excessive current.

Buying a used power stage is a real crap shoot. Some are good and some are bad and there is no real good way to test them with an ohmmeter since the failures tend to be around 50/50 between a shorted out unit like yours or one that is open and the blower never runs.
...Lee

I didn't hear anything out of the ordinary and it still blows. My friend says to go to junkyard and get 2 relays and 1 rheostat with fins behind glovebox. He also says there are 2 fuses - one for speeds 1-3 and other for speed 4. He says to test the fan if it turns freely - if it doesn't get a used fan too. It's easy for him to say, but this is all unfamiliar territory for me. You mention a power stage but he did not. Maybe you are talking about the same thing using different terminology.

Post by **Ozark Lee** » 17 Feb 2010, 16:35

The proper term for the ECC "blower resistor" is a power stage in Volvo vernacular. It is functionally the same thing but the implementation is quite different. The blower resistor is quite literally a wire-wound resistor pack and the "power stage" is a MOSFET transistor. The two fuses, one for speeds one through three and another for speed four is valid but only on the MCC units.

As I re-read the original post I don't think that we ever determined what type of climate unit you actually have. The ECC has settings that say AUT and the temperature settings are marked in degrees. The MCC has speed settings from zero to four and the temperature settings are graduated in varied width red bars.

If you have an MCC and the blower is stuck on with the key then the high speed blower relay is bad. I have never had one go bad but the smoke would not be unexpected if it back fed from the blower resistor.

Have you checked fuse number 31?

...Lee

Paul-93-850 · Post by **Paul-93-850** » 17 Feb 2010, 17:42

I have ECC - says AUT and settings are marked in degrees. Fuse 31 is good.

Paul-93-850 · Post by **Paul-93-850** » 17 Feb 2010, 18:36

I removed the lower dash panel on the passenger's side but now Glovebox won't come out. Forum post said "Next to the glove box door side of each of the arms there is a small hole. Slide the screwdriver into the hole and it will release the arm." This didn't work. Instructions don't say how far and how hard to push. I certainly don't want to poke all the way through. It's a very narrow hole by the way. Am I supposed to feel something, hear a click or what? Are 93's different?