Large voltage drop when using blower motor: Time to replace motor?

[MIDNIGHT RIDER]

No, only need one relay. Pretty sure I wrote this up already on here with the diagram.You did.

When direct HOT is wired through one relay, the blower does gain voltage; BUT, it still is burdened by a wimpy tiny Ford-style GROUND.


DRAMATIC blower performance is acheived by the addition of that second relay, which bypasses the factory system to a much better GROUND.



I have my blower relay switch wired KEY-ON-HOT, with an indicator light to tell me it is ON; of course, the indicator is sort of irrevelant, as the fact that my ears are about to blow off the side of my head is usually indication enough that the switch is ON.

 

[flitemedic]

'91 7.3 relay mod for blower

No, only need one relay. Pretty sure I wrote this up already on here with the diagram. I'll look for it after work.

For the 80-86...

Pull power from the heater select switch to pin 86 of a SPST relay, then connect pin 85 to ground. Run a 12g from the battery through a 20amp fuse, through pin87. Pin 30 goes to the hot side of the blower motor. The ground of the motor is what goes through the speed switch and ground and/or resistors on the lower settings.

'87-'88 are a little different. Simply need a key on hot wire to go to pin 86 of the relay.

Adrianspeeder

Would the above apply to '91's as well

 

[RKOCH]

Yes 2 relay system works much better.

 

[LCAM-01XA]

Okay, how about adding relay on my 1990 - what's the stock setup for that one, main power though the dashboard junction or whatever and then grounding through the switch? Or is it like a Chevy where it it draws the power through the switch and resistor coils, and then grounds through the mounting bolts?

 

[LCAM-01XA]

Aight, I went ahead and measured the voltage to my blower motor - it gets straight battery voltage all the time (14.2 volts with engine running), no matter what setting I have it on, so I take it as at least the supply circuit has been taken care of from the factory.

 

[MIDNIGHT RIDER]

Aight, I went ahead and measured the voltage to my blower motor - it gets straight battery voltage all the time (14.2 volts with engine running), no matter what setting I have it on, so I take it as at least the supply circuit has been taken care of from the factory.

Did you put the ground lead to the blower's lead, or to a different ground ??

 

[LCAM-01XA]

I pulled the harness off the motor, and measured what it feeds the motor, ground at the battery for most accurate reading.

 

[MIDNIGHT RIDER]

I pulled the harness off the motor, and measured what it feeds the motor, ground at the battery for most accurate reading.

Was the blower hooked up and running on HIGH-speed when voltage was checked ??


To get an accurate check on blower voltage, leave the blower connected, engine running, and put the meter probes into the plug-connection closest to the blower, both positive and ground.

Grounding the meter anywhere else will give a false reading as to what is really going on.

I had to make some little copper tabs to stick into the connections at the plug, so that I could access them with the probes.



If you are grounding the meter anywhere besides at the GROUND wire at the blower, you will be reading full alternator/battery voltage, regardless of whether the blower is actually getting use of it.


Make sense ??