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Author Topic:   Heater Blower Motor problems

Posts: 99
From: Conway, AR
Registered: Feb 2001

posted 01-13-2003 01:15 AM     Click Here to See the Profile for FiveLiterDreamer   Click Here to Email FiveLiterDreamer     Edit/Delete Message   Reply w/Quote
Hey guys I'm working on trying to figure out what is wrong with my heater blower motor and Im not having much luck. It stopped working about a week after I pulled the dash to replace the heater core. I've been messing with it, but something is confusing me. I'll try and explain it the best I can, so be patient. First of all, I pulled the connector at the blower motor and applied current to the four little prongs, on the heater unit, that go into the connector. Got Nothing. Out of curiousity i applied current to the actual connector and found that by touching one of the wires, the blower motor comes on. Next thing, leaving the blower motor connector disconnected, I also disconnected the connector that attaches to the heater control assembly switch underneath the dash on the drivers side. I then applied current to each of the four prongs. Once again, got nothing. I then applied the current to the connector wires. By touching one of those, I again got the blower motor to come on but only while the fan speed selector was on high. If i moved it to any position lower than "high", the blower motor shut off. Apparently, there are two seperate sources of current going to the blower motor, (since i can get it to come on by applying current to 2 different places), but I'm not sure why. Also, on the connector that connects to the heater control assembly, the connector was partially melted, but not real bad. I really need someone's help on this. It sure is cold. thanx

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Posts: 221
From: Port Royal, PA, USA
Registered: Nov 2000

posted 01-13-2003 03:35 AM     Click Here to See the Profile for Maxwell_fax   Click Here to Email Maxwell_fax     Edit/Delete Message   Reply w/Quote
Okay I'll give this a shot... WHen the switch in the dash is on high, it sends current directly to the blower motor...
The lower speeds are directed to an array of resistors (4 wire plug on the side of the heater box) Each lower speed is directed through a different resistor thus slowing the motor down..

The power to the switch on the control is also routed through the selector lever for heat, defrost,vent,off

Do I have this right so far guys/gals??

I had a problem with mine (I have A/C), and what had happened is the switch on the selector lever had melted along with the connector on the blower switch.. My connector was salvagable but I ended up bypassing the switch on the selector lever and removing the connector for the lowest speed on the blower speed switch.. The proper fix will be to someday replace the whole control...

Hope this is of some help...

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Posts: 34
Registered: Oct 2002

posted 01-16-2003 08:08 PM     Click Here to See the Profile for NoBS     Edit/Delete Message   Reply w/Quote

Yeah Max, I think you got it right. I believe the resistors are in the box to cool them and help keep from burning up. I guess it didn't/ doesn't always work.

How are the vacuum valves in your controol? They hiss a bit till you get them positioned just right? Mine does, then it doesn't always do what is indicated. I wonder if the A/C unit is rebuildable, or can be taken apart and cleaned. ?

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Posts: 221
From: Port Royal, PA, USA
Registered: Nov 2000

posted 01-20-2003 07:08 AM     Click Here to See the Profile for Maxwell_fax   Click Here to Email Maxwell_fax     Edit/Delete Message   Reply w/Quote
Mine did the same thing... I tried taking it apart but it was never really designed to do so... It kept coming back apart after that..

Luckily they are similar to the conrtols used on the early to mid 80's pickups... I had to switch 2 wires I think.... I also swapped the control from a Granada to an 80 F-100. Had to switch the wires the other way.. I think maybe the LTD's from about 79 to 91 were the same piece... The added bonus was the need little colored (blue to red) bar above the temp selector... It looks real spiffy...

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