850 fan alternate variable resistor—let's get creative!

[JimBee]

A couple of years ago I bumped into a guy who had a beater 850 with actual working a/c but a bad ecc. He direct wired the fan with an on/off switch, not ideal but it kept him cool.

My 93 850 ecc dash fan control isn't working. I haven't given it a lot of diagnostic time and it's too cold now to mess with it (and my 96 base does have a working mcc, so I have that option to drive).

I suppose the dampers on the 93 can be manually adjusted to pass heat to the cabin if they're not already in a proper position.

Reflecting back on the beater 850 guy's solution, could I just cut in a heavy duty variable resistor for the fan and eliminate the complexity of all the sensors?

Maybe something like this:
https://www.amazon.com/RioRand-9-60V-Mo ... 7893&psc=1

Let's get creative!

[Clemens]

I'd try a used ECC first, but I think there were different parts numbers available. I think they have to match. I had a broken ECC years ago and got a used one. Been working ever since.

[scot850]

Been a while, but I think Clemens is correct. I think there was a possible change in 95 or 96 on the units numbers.

From this link, although they are now long NLA, if you scroll to the bottom where the retired/discontinued numbers are, just look how many part numbers there are!! I count 15!! Yikes. Some state the part number replaces another on the list, but not all. This does not include MCC.

https://www.volvocarstorontoparts.ca/a/ ... 69096.html

Neil.

[JimBee]

I know the blower motor fuse is good, but I suppose I should determine if the ecc unit is actually being powered and if there's power in am I getting power out. I don't have a schematic for probing the various pins; the main lead to the resistor is easy enough to probe. I just ran out of time for this project and then it got too cold.

If it warms up a bit to the 30's around here, I'll probably look at those circuits closer. The only codes that I got were for the driver's side door-top sensor fan which I cleaned out (that code went away), and the outside temp sensor shorted to ground. From reading up that temp sensor doesn't seem to be a circuit breaker, but I'm not sure.

I bought a new resistor pack from Volvo which they told me was now generic, so supposed to work with any of the 850 ecc's. That didn't change anything. The fan had been working okay, though I had gone inside that one and cleaned it up and regreased the bearing, so although it turns by hand easily it could be binding a bit but it's not taking out the fuse.

So questions remaining: If there's variable power out from the slider to the resistor. then is there power out of the resistor to the fan?

That Amazon variable resistor is looking awfully tempting as a short term fix

[Clemens]

I have no idea, but I wish I could be of more help. Please keep us updated.

[DennisCA]

I had an issue with my blower and it turned out the issue was the connector, it had melted before and was making really bad contact. I replaced the connector with some abiko connectors and now it works fine again, wires or connectors don't get hot.