Blower Fan won't stop -1994 c280(w202)

[Mike2010]

I just bought a 1994 C280, price was right. This is my third C280, I bought it at a low price and knew that it had problems. Worse case its a parts car, but it only has 120,000 mi. Here are my problems.

1.The blower fan starts running as soon as you turn on the key, and it eventually blows hot once the car is hot. It also continues to run a few seconds after you turn the key off. It doesn't matter what you do with the ACC system buttons, it runs at what I think is wide open.
2. It idles poorly.
3. The previous owner removed the Duovalve and bypassed the aux coolant pump below the air filter housing.(Not sure why)

My code reader says:
P0116 - Engine Coolant Temp CKT Range/Perf
P0101 MAF VAF Range/Perf.

Granted, the poor idle is probably the MAF.
I suspect the coolant temp sensor is telling the ACC that the car is overheating and is running the heat at full speed to dissipate the overheating. Or maybe I have a bad relay or a bad ground.

Any ideas?
Thanks in advance.
Michael Towns

[whunter]

Originally Posted by Mike2010

I just bought a 1994 C280, price was right. This is my third C280, I bought it at a low price and knew that it had problems. Worse case its a parts car, but it only has 120,000 mi. Here are my problems.

1.The blower fan starts running as soon as you turn on the key, and it eventually blows hot once the car is hot. It also continues to run a few seconds after you turn the key off. It doesn't matter what you do with the ACC system buttons, it runs at what I think is wide open.
2. It idles poorly.
3. The previous owner removed the Duovalve and bypassed the aux coolant pump below the air filter housing.(Not sure why)

My code reader says:
P0116 - Engine Coolant Temp CKT Range/Perf
P0101 MAF VAF Range/Perf.

Granted, the poor idle is probably the MAF.
I suspect the coolant temp sensor is telling the ACC that the car is overheating and is running the heat at full speed to dissipate the overheating. Or maybe I have a bad relay or a bad ground.

Any ideas?
Thanks in advance.
Michael Towns

It appears the aux cooling fan is the bad sensor = P0116 - Engine Coolant Temp CKT Range/Perf
I agree on the MAF diagnosis.

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[Mike2010]

WHunter, Thanks for the post.
The dealer said there were two temp sensors, both in the thermostat housing. One for Gauge, and one for Climate control. I plan on reinstalling the duovalve Saturday, and doing more troubleshooting afterwards. I am not sure if the aux fans are coming on or not. Didn't want to let it get too hot.

[whunter]

Originally Posted by Mike2010

WHunter, Thanks for the post.
The dealer said there were two temp sensors, both in the thermostat housing. One for Gauge, and one for Climate control. I plan on reinstalling the duovalve Saturday, and doing more troubleshooting afterwards. I am not sure if the aux fans are coming on or not. Didn't want to let it get too hot.

If you where talking about the climate control cabin blower motor?

The most common issue is a failed blower REGULATOR MB# 2028202510

FYI
The temperature sensor for the aux fan should be MB# 0115425117


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[Mike2010]

Sorry for the extreme delay in posting. Installed duo valve. Turns out previous owner had removed thermostat. BAD. Overheating was caused by failed aux fan, which blew fuse on relay located behind fuse box, casuing neither fan to operate. Also by not having thermostat installed. Over heating problems solved.
Heater Fan blower problem caused by regulator. Replaced it, problem solved.
ALso repalced Mass Air FLow, which helped idle. Now have poor cold starting. Perhaps it is the Engine Coolant Temp sensor? Hmmm.