Blower Motor 1991 300E Info
 

Thanks for the help with the strip fuse issue. The fuse was broken but did not appear to have melted as with a conventional burn-out. It looked more like it corroded. It has been replaced, but still no blower power!

I have read some helpful posts by Arthur Dalton and Shavereng but have a couple of questions,

The strip fuse has 14.8 volts across it now that it has been replaced.

The X64 connector, blower speed control, was located as mentioned, above and behind the booster assy. Mine has red, yellow and a black wires. I am assuming the black wire I have is the "blue" wire refered to by Mr. Dalton. Should I test the voltage at the wires or the male connection on the firewall? I tried both a short time ago but we are having wind gusts up 50 mph today and my meter was in danger of being carried off to Oz.

Is the cabin air recirculator switch on the same circuit as the fan controls?

What part if any does the heater core temp. sensor play, I can't locate it on my schemantics.

Thanks

<<The strip fuse has 14.8 volts across it now that it has been replaced>>

Across the Fuse ??
What does that mean???

I assume you mean you now have 14 volts before the fuse and 14 v after the fuse , using the fuse connections for positive and ground for neg. ????

14 Volts
 

Quite right, I mis-spoke. I meant that I had 14V on either side of the fuse when tested to ground.

I had a blower motor that was intermittent once. It turned out to be the plug you mentioned. Simply dirty connections. Sounds like you've ruled that out.

Much better..

Ok
At the 3 prong plug, you should have 12v from red to blk. If so , then you should have a variable voltage from yellow to blk, depending on what speed selection the control panel is looking for ..This will be from about 3 to 7 volts . That is trigger voltage for the regulator.
The blu wire I mention is at the blower motor itself and is the ground side of the motor . The red side of the motor is alway HOT and the blu wire attains ground to complete the circuit through the regulator. In other words , this is a SWITCHED GROUND cicruit.

Check the plug and see what you have... key ON

Three Prong Plug Tested
 

I tested the three prong plug as suggested. Red to black, 0 voltage. Yellow to black, 0 voltage.

Key ON and fan ON ??

Defrost position will give Max fan for testing purposes...

Plug Test
 

The test was done with the engine running and the fan set for high with floor and dash heat. Wheel set to 85 degrees. Test done on wired end of connector not affixed end.

Which means the firewall feed side of connector???

Connector Test
 

The three wire connector was disconnected from the end of the connector that is affixed to the firewall. The voltage was tested on the wires forward of the firewall and not on the end that is connected to the firewall itself.

Wrong place..

For future testing on ANY plug connectors , if one is not sure which side of the plug is the live feed side, you simply just test BOTH sides...........................

Test Complete
 

Since I was unable to get my hands or the meter probes into the tight spot where the hard-mounted side of the connector resides, I picked up the same connector with wires attached from a local auto recycler. This allowed me to plug into the firewall connector and easily access the wire stubs with my meter.

Protocal:
-Key on, engine running
-Defrost position selected and depressed
-Fan speed set to high
-Wheel set to 85 degrees
-Engine not up to operating temp. since "key on" only was suggested

Results:
-Red to Black, 14.4 to 14.7 observed
-Yellow to Black, wildly erratic and non-sense readings observed

Is a new fan regulator the next step?
Thanks

Ok

Now the hard part
You have to get down to the fan motor and ground the blu wire . This takes the regulator out of the circuit [ by-pass] .. See if fan runs when you do that...
I do not know why you have the engine running for these test ???
...as I stated in the test procedures , "Key ON" and Defrost will suffice......

The Blue Wire
 

Off I go in search my blue wire!

The engine "running" thing is really only a means of staving off frost bite, the high at the Connecticut shore was about 26F today. Ever the practical one.

Based on your Florida/N.H. notation I can only hope you are down south right now!

Yikes!!! Proceedure Reviewed
 

You were not kidding about the "hard part". I just finished reviewing and printing-out a very well done proceedure illustrating the accessing of the blower motor assy. in the DIY area of the site.

This will have to wait for a warm spell. Thanks for the help to date.:book: