Troubleshooting AC + Heater
Hotshot
Joined: Jun 2015
Posts: 12,885
Likes: 2,448
I'm confused. There is only one plug/connector that supplies power to the motor which should be pretty obvious. I guess that is what is pictured in the top photo. It's hard to see what you are talking about. The motor should run in high if it has 12v to it. The resistor(s) lower the voltage to slow it down for the other 3 speeds.
That link in the next post is for ignition parts. I'm not sure what that has to do with the blower motor not working.
That link in the next post is for ignition parts. I'm not sure what that has to do with the blower motor not working.
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Senior User
Joined: Apr 2016
Posts: 291
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From: Austin, TX area
Quick question - can I drive the truck with the heater blower motor completely disconnected? Or will that prevent a circuit from being made on other equipment? I'd like to take out the old one but still have use of the truck while I wait to afford replacement parts.
Obviously it wouldn't get any heat or AC but I'm already in that position. hahahaha
Assuming the heater blower motor is the culprit, would that prevent everything from even turning on in the heating/cooling side? i.e. the AC compressor won't turn on because the blower won't work first? I thought by fixing the vacuum line I would get the AC to turn on, but it wouldn't blow until I fixed the motor. Is that logic incorrect?
Obviously it wouldn't get any heat or AC but I'm already in that position. hahahaha
Assuming the heater blower motor is the culprit, would that prevent everything from even turning on in the heating/cooling side? i.e. the AC compressor won't turn on because the blower won't work first? I thought by fixing the vacuum line I would get the AC to turn on, but it wouldn't blow until I fixed the motor. Is that logic incorrect?
Hotshot
Joined: Jun 2015
Posts: 12,885
Likes: 2,448
If it turns out that the blower motor is bad that will have no effect on the rest of the system. It should all work but you won't have air blowing out of the vents. Checking for power at the blower motor only takes a minute or less. I'm not sure why you still haven't checked particularly when you were right there fixing the vacuum hose.
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Senior User
Joined: Apr 2016
Posts: 291
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From: Austin, TX area
@Lead Head
I haven't heard the A/C click at all, but I'll specifically check for it.
@My4Fordtrucks
Only so many hours in the day.
I knew the vacuum hose needed help and ran out of daylight twice while working on that.
I plan on working on the truck more tomorrow. Might even buy a new blower motor if I sell a few rain barrels.
I haven't heard the A/C click at all, but I'll specifically check for it.
@My4Fordtrucks
Only so many hours in the day.
I knew the vacuum hose needed help and ran out of daylight twice while working on that.I plan on working on the truck more tomorrow. Might even buy a new blower motor if I sell a few rain barrels.
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Senior User
Joined: Apr 2016
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From: Austin, TX area
OK, I took a look at the heater blower motor etc last night. Here's what I learned:
The motor itself works. I took it out entirely, expecting it to be completely toast due to its age. But, it appears to be in 100% working order. I tried my 12v 1000mA wall wort with it and it worked instantly. I did the same with my battery starter hooked to alligator clips - same thing. So the motor seems fine.
I took the opportunity to clean out the area of leaves & debris next to the heater core fins etc just past the blower motor. I'll hit it with the vacuum too just to get out 27 years of crud out of there.
Next I hit the fuse/relay that is mounted right next to the heater blower motor. I had watched several videos about how that part goes bad and needs to be replaced. That thing was a son of a mother's goat to get out of the truck. Worse, I can't tell if it's bad or not. None of the coils are broken, but one little piece of wire seems corroded for a few millimeters.
Have a look at the image - it's high rez so you can zoom in after the link.
heater blower motor and fuse
Here's the close up image.
heater blower motor fuse / relay
The motor itself works. I took it out entirely, expecting it to be completely toast due to its age. But, it appears to be in 100% working order. I tried my 12v 1000mA wall wort with it and it worked instantly. I did the same with my battery starter hooked to alligator clips - same thing. So the motor seems fine.
I took the opportunity to clean out the area of leaves & debris next to the heater core fins etc just past the blower motor. I'll hit it with the vacuum too just to get out 27 years of crud out of there.
Next I hit the fuse/relay that is mounted right next to the heater blower motor. I had watched several videos about how that part goes bad and needs to be replaced. That thing was a son of a mother's goat to get out of the truck. Worse, I can't tell if it's bad or not. None of the coils are broken, but one little piece of wire seems corroded for a few millimeters.
Have a look at the image - it's high rez so you can zoom in after the link.
heater blower motor and fuse
Here's the close up image.
heater blower motor fuse / relay
Last edited by TexanAmmo; Sep 13, 2016 at 10:46 AM. Reason: Added better image
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Senior User
Joined: Apr 2016
Posts: 291
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From: Austin, TX area
Heater Blower Motor wiring
OK, so if the heater blower motor is not the issue, nor is the resister, what do I check next? I can check the power if I am told how. I have the tester light - ground to something nearby and then test either prong in the plug?
The wiring leading from the cabin firewall to the blower motor looks fine. Nothing crimped, bent, exposed, etc. The wiring DOES have a barrel on it that I haven't seen before. See the photo below.
Heater blower motor wiring 2
Fleet Owner
Joined: Aug 2005
Posts: 23,668
Likes: 301
From: Easton,Ks
Hook you test light between the POS (+) battery post and the Orang wire with a black stripe.
Turn the blower switch on HI.
The test light should light. Dose it?
If yes then hook you test light between the NEG (-) battery post and the Brown wire with a Orange stripe.
With the key on the test light should light in any position of A/C-Heater function selector switch except off.
Turn the blower switch on HI.
The test light should light. Dose it?
If yes then hook you test light between the NEG (-) battery post and the Brown wire with a Orange stripe.
With the key on the test light should light in any position of A/C-Heater function selector switch except off.
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Senior User
Joined: Apr 2016
Posts: 291
Likes: 0
From: Austin, TX area
Thanks for helping subford.
I believe in order for this to work I need to put the resistor back in first, don't I?
That & the blower motor are both still out. That's how power gets through correct? First to the resistor then thru to the power to the motor, right?
I believe in order for this to work I need to put the resistor back in first, don't I?
That & the blower motor are both still out. That's how power gets through correct? First to the resistor then thru to the power to the motor, right?