Hey Everyone,


I've been doing a lot of searching on this topic and wanted to do a quick check before I continue to throw parts at the problem.

1994 850 Turbo Wagon, Automatic Climate Control, 232k (I've owned for almost 8 years, since 140k)

Issue: About a month ago the blower motor stopped working, this was after years of slow decline where it would work but make noise, then after hitting a bump the noise would go away. At highway speed it would still allow cool or hot air into the cabin depending on the temp selection, but at a low flow rate. I pulled the codes and got a bunch (126, 417, 418, 419) including the failed passenger cabin temp sensor over the door which has been an issue for a while but hasn't affected the system noticeably.


Current status: Last night I replaced the blower motor (new OEM Behr) and blower resistor (new Volvo OEM) and still have no fan. There is 12VDC at the blower plug, and when you turn on the car the blower runs for about a second then turns off. I tried the blower with the car running, not running, all key positions and fan positions, no luck. I cleared and pulled the codes again with these coming back:

126, 417 (passenger temp sensor shorted, pass temp fan seized)
419 Faulty diagnostic signal from blower fan power stage

Next steps: From what I can tell the ECC control unit needs replacement but I wanted to see if there was anything else I may be missing. From my research the blower motor fails, it draws more current from the resistor which eventually fails, then at some point it takes out the ECC control unit. Not sure if this is accurate, hence me asking. I removed the ECC and haven't noticed any burned up smells but who knows.


Any tips would be greatly appreciated. I'll most likely go with a ebay ECC unit for $60 so I have something to work with this week.

Thanks,













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Zack 94' 850 Turbo Wagon (232k)

Update 10/13/14

New (used) ECC unit arrived in the mail today so I plugged it in hoping for a miracle...

No such luck. Same symptoms as before, codes 126 (Pass. Side Temp. Sensor
Circuit Open Or Shorted To Power) and 419 (ECC Power Stage Emitting Faulty Diagnostic Signal). Started troubleshooting the wiring and did not find any shorts, there was continuity between the wires on the back of the ECC and resistor, etc where there should have been. I would have liked to go further with troubleshooting but without the test unit (981 3190) and adapter (981 3194) I'm not sure what else I could do.

The blower still runs for about a second when starting the car, and when the ECC power stage (resistor) terminals are shorted the blower runs on high and pulls about 17A of current (engine not running). I tried the old power stage and it threw code 418 (No Control Signal To ECC Power Stage) and the fan did not run for one second when the ignition was turned on.

I guess the next step is to replace the passenger side temp sensor to clear that code, but I'm doubting it will do anything to help the blower situation.

Has anyone seen a a power stage DOA? I bought this one new from IPD, it's Volvo OEM and has the exact same part number as the previous unit.








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Zack 94' 850 Turbo Wagon (232k)

Did you clear the codes with the new unit? What troubles me is that the blower works during system checkout and then everything fails. More like a wire to the power stage is shorted.

It is quite possible that the new power stage is inop.
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My back feels better when I sit in a Volvo seat

When I first plugged in the new ECC unit there was a whole list of unrelated codes. After clearing those I did some troubleshooting (trying the old power stage, etc..) creating some new ones but re cleared those as well.

For now I'm back to 126 and 419. I'll dig back into the wiring between the power stage and the ECC to make sure there aren't any shorts. Some of those wires are under foam insulation which I'll need to open up for inspection.

I'll also see if I can source another known working power stage to try out, I'd hate to have received a DOA brand new unit.

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Zack 94' 850 Turbo Wagon (232k)

After hours of checking wires and troubleshooting the conclusion was that the brand new power stage was DOA. I ordered a used one from ebay, installed it and the blower is now working.

Thanks for the suggestions, and take this as a lesson that even brand new OEM parts can be bad out of the box.


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Zack 94' 850 Turbo Wagon (232k)

http://www.partsgeek.com/catalog/1996/volvo/850/climate_control/a-fs-c_control_unit.html


here is a rebuilt ecc......spensive........

Did you get the correct power stage, resistor? Not the cheaper one for the MCC.

It sounds like the ECC unit is still good. Don't trash it yet. The fact that the blower runs for a second at start up means the ECC unit is going through the system checks. The blinking lights means there is an error.

Get it fixed before it gets cold!!

You do realize that the 'auto' function will not work until you replace the cabin temp sensor. This has nothing to do with the current problem, just getting ahead of myself.

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My back feels better when I sit in a Volvo seat

Klaus,

I ended up ordering a replacement ECC from ebay yesterday ($60) and plan to try it out upon arrival later this week. The replacement resistor is the same as the previous (volvo oem, specific for automatic climate control) so I think we are good there.

I'll also order the cabin temp sensor so that once this is all said and done there will be no more flashing lights and my wife can stay warm when the snow starts falling.

Thanks,





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Zack 94' 850 Turbo Wagon (232k)

Why not visit a bone yard: and get a new blower motor, and the dead sensor, and start by replacing known bad parts? Those codes are telling you something?

Willie