Heater blower motor resistor question

[Timber]

My fan only works in the high position, so I was told it had to be the resistor. I took it out and it was corroded badly but not broken so I cleaned it up and checked continuity. It tested good between all poles so I put it back in. Still no joy. Then looking at the plug I noticed I'm missing a wire. What goes here - ground maybe? There is a corresponding pole on the resistor but I don't have a wire in that spot of the plug.

 

[joshuak]

I don't think you are missing a wire, mine is the same way and electrical diagram F-20 has 4 wires going there, so you should be good there. Have you tried cleaning your blower switch?

 

[Timber]

I have not. I've started putting together a cluster of gauges to replace the idiot lights and planned to be "in the dash" maybe next weekend so I'll check it then. I'll be the first to admit my test might not have been correct. After looking at the resistor and thinking about it a minute I checked the connected poles for continuity thinking if it had it, it was probably still good a part but that may not be the case.

 

[cucvrus]

I will put my money on the blower switch or the plug on the blower switch or both being bad. You can lay on the floor and look up and see the plug on your blower switch. I put one in on the road already just by unplugging it and plugging a new one in. i had no tools and the heat stopped. Beat freezing I was in Maine. I just controlled the heat with the cold-hot slider.

 

[Timber]

Only the plug failed? How does that happen? Short of physical damage or corrosion, which you wouldn't really expect either with it tucked up in the dash, you'd think the plug would outlast the switch.

 

[cucvrus]

The plugs and the switch are know to fail. It is a poor connection and it makes resistance thus causing heat build up over time. I have seen it on many CUCV's. At one time when the pigtail was available from GM it was a $40. item. I cut everyone out of every GM vehicle I see at the UPULLIT. The switch knobs fit from Buick and Pontiac also. I have black heater control knobs on my Mule.

 

[Timber]

I'll check it tomorrow and see if I'm getting voltage at the resistor plug at different speeds.

 

[MarcusOReallyus]

I cleaned it up and checked continuity. It tested good between all poles

Did you check the actual resistance? Or did you just use the continuity check function on your multi-meter?


If the resistance isn't correct on each pole, your blower will not get the lower speeds. One of the lower speed poles could be shorted, which would give you good continuity, but allow the motor to operate only at full power.

 

[Timber]

I didn't check resistance, just continuity. The backside looked like different sized stove burners so I thought if the connection still existed they were working. But like I said, I was winging it and haven't messed with one before.

 

[Timber]

I'm only getting current to one position of the plug and only in the high position. I looked under the dash at the switch and didn't see anything obvious. Later this week I've got to pull the bezel and cluster anyway so I'll get a closer look then. Thanks for all the help.

 

[cucvrus]

I think that is normal the switch puts the electric to the resistor and sends back the proper voltage thru the different wires and you get different fan speeds. I am a simple man and these are just simple terms. And that is how i understand the system to work.

 

[Timber]

I finally got in there today. The switch is bad, a few of the terminals on the backside are cooked and melted. The plug appears to be fine. LMC sells the whole assembly. Will those work with our trucks? It's part # 32-0638 on their website. It looks like the same one in the truck, but I know ours have the HD resistor, so just want to be sure. Thanks.

 

[Timber]

I went ahead and ordered it. I'll report back how it works.

 

[kkcshipp]

My blower stopped working, what did you order? Pics? Where is it located?

 

[cucvrus]

If I had to guess> I would say it is the blower switch in the dash. that is my guess. You can see it if you lay on your back and look up there from under the dash. Check it out and let me know. Also the fuse. Check that. Was the motor noisy?

 

[kkcshipp]

We took it out. Looks like it's cooked. Going to pull it place on Saturday to try and find a replacement. First pic shows it pretty well. I'm going to replace all fuses, just don't know if any are missing.

 

[cucvrus]

That switch is nothing special. I buy them at many parts stores. Use some dielectric grease on the connection and make sure the connections are tight. They have a tendency to be loose at the connection and that is what has caused the hot spot on the switch. It lasted 30 years so if you just replace it and use some care it will last 30 more. And after that who cares? Merry Christmas.

 

[Timber]

If I had to guess> I would say it is the blower switch in the dash. that is my guess. You can see it if you lay on your back and look up there from under the dash. Check it out and let me know. Also the fuse. Check that. Was the motor noisy?

Yes, that's exactly what it was on mine. Glad to see you reinstated and thanks for your help with mine. FWIW, don't bother with the LMC controls. The hot/cold slider and vent position slider feels cheap. Also the fan switch only worked intermittently. Looks good, but I don't think it will last so it's going back. Cleaning up your OEM controls and replacing just the switch is the ticket.

 

[kkcshipp]

Replacement switch purchased at Autozone, part#SW196. Will put back in after the UK/UL game and report results.

 

[kkcshipp]

Fixed it!