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Old 09-12-2002, 06:37 PM
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Join Date: Dec 2001
Location: Rocklin CA
Posts: 65
W140 AC Problem

96 S500. AC blower stopped working. Just replaced the blower regulator. Blows again except now the "auto" function is erratic.

Let me give you the symptoms.

98 Degrees outside Inside both driver and passanger set to 73% and auto. AC barely blows. If i move the temp down to "low" on both(only doing one doesn't work" the AC blower goes on full throttle. If I go down in temp but not quite to low, no change. I can also hit the little blue button in the center vents and set the fan manually and the blower goes correctly. What could be the problem, the temp sensor?

I had the blower regulator changed at a shop, but I took the cowling and stuff off when I was troubleshooting. I didn't know what I was doing and there looks like there is a vacuum operated flap over the blower that is probably activated by the recirculate button on the center console. I took off the vacuum connector to this flap and when I put it back on I may have done it wrong. I don't think this has anything to do with the problem of temp activation, but thought I mention it.

Any ideas would be much appreciated.

I can give you the troublehsooting readout using the rest button if you need them.

Anyone want to start me in a diagnosis direction?

Ken G
96 S500 79K (great white whale)
98 E430 80K Sports Package (gray ghost)
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Old 09-12-2002, 08:11 PM
JimF's Avatar
'94 S500: only 793 sold!
Join Date: Mar 2001
Location: San Diego, CA
Posts: 1,925
Well, no expert here. . . .

because I've never had a problem with the A/C (tnx God!).

But does sound like a temp sensor problem. In my car, there's a differential temp that when you rotate the wheel(s) to a colder temp that exceeds this inside temp differential, the blower then picks up the fan speed.

So in your example, of 98F outside, I would think that setting the temp wheels lower than 70F or so, should send the blower into high(er) speed operation.

Need a pro hear that knows for sure but you can list the code(s) from the A/C diag readout for info.
Regards . . . . JimF
'94 S500 Cpe

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