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Old 11-18-2002, 05:37 PM
pmizell's Avatar
Benz Zealot
 
Join Date: Jun 2001
Location: Houston, Texas
Posts: 838
No blow blower diagnosis

My blower motor has been working off and on for the past couple of months. From previous threads I'm trying to diagnose whether the push button control unit is faulty or if its the blower regulator. I've tried the jiggle-the-ignition-switch trick and have ruled that out.

When I voltage test the 3 wire firewall connector I'm getting 12v power from middle wire and 7v from control wire ALL the time whether PBC is turned off or on, and at any setting. (when it is not working) Of course I can't get it to run today, so I haven't been able to test current when blower is working.

When blower won't respond to PBC input I can hear the blower on a very low setting and it blows hot air out of the defrost vents. When in this mode, I get a solid LED light when I test AC fault code pin.

Also, sometimes when blower is not working while driving, it will turn itself on, without pushing any buttons on PBC.

This leads me to believe that it's the voltage regulator.... but still not sure.

Any help would be appreciated!

Thanks in advance
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-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi
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Old 11-19-2002, 05:03 AM
pmizell's Avatar
Benz Zealot
 
Join Date: Jun 2001
Location: Houston, Texas
Posts: 838
Finally got the blower to turn on..

and I tested voltage at the 3 pin firewall connector. Same results -- 7volts DC on any setting. Based on an archived post where post mentioned that if voltage is same when blower is working and not, then the regulator is fried -- I was almost positive the regulator was bad.

Well, I was all set to order a blower regulator when I came across this Steve B post:

Quote:
If the control voltage as measured on the connector behind the vacuum boost stays at a constant 7 volts, then the odds are your ACC has been damaged. Check all your fuses and retest the voltages. If no change, then I'm betting ACC module.
Steve, if you read this post, please elaborate. What is it about the 7 voltage reading that leads you to believe the PBC unit is bad?

I'd really hate to pull the blower only to find out the PBC needs to be replaced. (all solders look good)

again, TIA!
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-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi
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