blower motor help

[swamprat]

I have a 1989 BII that the blower quit on a few weeks ago. I doesnt work on any fan speed. I took a volt meter to the plug at the motor and have ground but on the other I have a neg 12 v. What is with that. Checked fuses and all are good. What is going on?

 

[MAKG]

You just hooked up your voltmeter backwards. Nothing more. Repeat the test with the probes across the motor. You did step #2.

 

[swamprat]

Yep leads were backwards. Loaned it out last week. I swapped blower motor to see if it was the motor it self and got same results. When I turn on head lights the lights on fan controls goes off. Could it be the fan and heater control causing the problem? Any thing else I should check?

 

[backerm]

did you check the relay?

 

[MAKG]

It sounds more to me like a missing ground, and the fan is finding ground through the hot side of the headlight circuit. If the headlight switch is open, the resistance through the headlights is zero. I'll bet your fan is pretty weak, too.

 

[swamprat]

It worked fine untill two weeks ago when I replaced the windshield washer pump. The next day I went to turn on the blower and nothing. I wouldnt think that they share a ground. I checked the ground side of the plug to the blower with the multimeter and it was good.

 

[Mark_88]

I'm betting on the little relay that is plugged into the heater box itself and is held there by two screws (where the wires connect to the box itself). This went out on my Ranger and although I did have high speed only for a while, it eventually quit. That connector has a resistor spring inside that corrodes over time and can short out the whole blower fan...I tried changing the fans too and that was not the problem...try disconnecting the wires from the heater box and remove that connector by undoing the two screws (they look like bolt heads but are actually screws). If you find the connector badly corroded then you might try replacing it.

The F150 and others are similar and will work, but you may need to change the wires around a bit to match up. The F series heater boxes are angled (as are some BII and Rangers with A/C) and because of this they tend to not corrode as badly as the Rangers do...probably because they do not get as much direct road spray...

If you have to go this route and replace that switch, make sure you cut the wires long so you have enough wire to play with as it can be very difficult to connect them when the wires are too short to work with...found that out the hard way...

 

[swamprat]

got a chance to check it out again. I hooked a jumper to the ground on the blower motor and it ran on high in all speed locations and when it should have been off. Took the relay thing out and it looked fine. Cleaned out some leaves while I had it out. I get continuity on both wires goig to the blower motor for ground. Does any body know what wire should be the ground? I think it should be the orange with black line. I does look like the headlight and blower are sharing a ground. Does any body have an idea where these two could be? Am I looking for some worn wires with bare spot?

 

[Jorley]

Hey. I don't know if you got it fixed yet so here goes. The hot wire coming from the fuse box is brn/org. It runs straight to the motor. the orn/blk wire goes from the motor to the blower switch for hi and to theblower resistors(that relay thing on the plenum) from there 3 wires go to the blower switch for the various speeds. The Lt grn/wht will have the highest voltage, the yel/red less and the red/org the least. From the blower switch to ground is a blk wire. If the blower works on high the motor ,switch and ground are good. Check the volts from the resistors. If it doesn't work on high check the motor switch and ground. A good way to check the switch and ground is to unplug the motor ,turn the blower switch to high and measure resistance to a good ground(make sure to only check the orn/blk wire or you will fry your meter) ,should read 0 ohms or a very low number. hope this helps and sorry so long.

 

[Jorley]

About the headlights and blower sharing a ground, my chilton's manual(where I got the wire colors for my other post) shows that only share the vechile ground. The blk wire from the blower switch goes straight to ground.

 

[Mark_88]

I would hesitate to look any further than the relay switch since the blower is actually working. When you took out the relay did you check the connector for rust (disconnect the plug from the relay)?

I've had the exact same thing happen twice on two different trucks and they always work on high but nothing else...that's the relay gone bad or the connector corroded...when I changed that relay with a good one it worked properly both times...I would even suggest swapping in both ends of the plug instead of trying to use just the relay...and maybe grab a spare one if you can find it (in the junk yard since new ones are probably expensive)...

There may be something else happening with your wiring, but I would recommend just changing the relay first...it's simple enough to do as long as you cut the wires long...as in close to the plug on your truck and farther up the wire on the doner vehicle...


I will try to get a pic for you of the one I have done on this truck...I got busy with trying to get the motor started last night and that took up most of my time...I will see what I can do this afternoon, but it's really warm here today and I wanted to get the truck running...have to work out the fuel line restriction but that shouldn't take more than an hour...

 

[swamprat]

I have been working 6 days a week and about 65 hours. I got tired of it not working so I hooked a ground wire from the plug on the blower to a toggle switch that used to go to some fog lights that are gone. Now I have a blower working till I get more time to work on it. The light on the air control works now so there is a problem with the gound wire somewhere.

 

[khooper]

you could bypass the limit switch to see if that is the problem shut down all power to furnace take the wires off the limit switch get your self a piece of wire and connect one end of the wire to one of the wires to switch and the other end to the other wire via wire nuts or insulated alligater clips restore power then turn it to heat if it comes on you know it was your limit switch.

thats what I did when my gmc r30 blower motor got problem. Hope it works for you.
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KHooper