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#1
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Blower regulator test
I spend about 2 hours this morning replacing the blower motor on a 87 300d,just to find out that nothing is wrong with the old one...ACC seems to work fine,pushing the buttons I can hear the valves working,also I tested the blower regulator behind the brake booster? and got power on the red wire.My questions is,how can I make shure that is the problem,can I bypass that regulator,jump the wires?
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#2
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Power at the red wire simply means you have 12v feed from the fuse box.
The regulator is in the ground line for the blower [ switched ground] and it is triggered by a variable voltage from the yellow wire coming from the PB unit. Look for 2-8 volts at the yellow wire with the PB unit ON. If you have that, then the reg is not tripping. In that case , the blue wire coming from the neg side of the blower motor to the regulator can be jumpered to ground. If the motor then works , you have a bad regulator. Just make sure you have trigger volts at the yellow before diagnosing the reg. as bad.... |
#3
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Quote:
I did my test on our W124 500E since I have NO blower movement, and here are my results: On the 3-pole connector, I have +12VDC on red; good continuity to ground; and 7+ VDC on the yellow control wire on HIGH & Defrost, about +2VDC on "low" speed. How can I bypass the regulator and access the blower motor directly to see if the blower still spins/works ? In other words, is there an accessible blower power connector that I can access to add 12VDC ? TIA, :-) neil |
#4
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The blower pos. is hot all the time . It is the ground side that the reg switches..
So, as I stated in the test post, you ground the blu wire that goes from the motor to the reg. If the blower then works, the reg is not working [ assuming the reg is getting trigger voltage at the yellow wire.] That is all the regulator does .. it switches the ground side of the motor. [ called a Switched Ground] |
#5
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Ugh! Which means I have to PULL apart the unit first!
:-( neil |
#6
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There was also some discussion about the motor having a bad ground thru the screws. Check the resistance to ground from the motor frame!
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#7
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Quote:
That's why we have you check the firewall plug for power first. |
#8
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Quote:
I think the post you are referring to is the ones that the fuse block mounting screws get tightened too much and ground out... different proble/diagnosis. |
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