SOLVED: New Heater Blower, new fuses, still no work

E28 technical advice asked and given! Troubleshooting, modifications and more.
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matreyia
Posts: 64
Joined: Dec 22, 2021 1:05 AM
Location: Houston

SOLVED: New Heater Blower, new fuses, still no work

Post by matreyia »

Hi Everyone, so this is the last thing to fix on the 1988 e28 before I move to body work.
I replaced the heater blower motor, all new fuses and the blower still doesn't work when I deactivate the AC button with the temperature set on high. Am I doing something wrong?

I assume the AC button is the same as the heater button when deactivated so it works. AC is cold as ice as I just fixed the auxiliary fan - replaced that fan with ebay used one and replaced the resister too.

So I'm stumped. Using same model motor as the original one in the car. Any ideas?

:shock:
Last edited by matreyia on Jun 02, 2022 5:11 PM, edited 1 time in total.
Mike W.
Posts: 26872
Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: New Heater Blower, new fuses, still no work

Post by Mike W. »

There is no heater button although the A/C button does switch power between the two.

Looks like the path is thru the A/C switch, and they have been known to fail, to the blower motor. So ignition on, you should have 12V at the blower. The ground side is where it gets a little more tricky, going from the blower to the heater resistor module, to the fan speed switch, which is effectively a double switch with one part for A/C and another for the heater, to ground.

So, verify power to the blower, then find out where you're losing ground.
matreyia
Posts: 64
Joined: Dec 22, 2021 1:05 AM
Location: Houston

Re: New Heater Blower, new fuses, still no work

Post by matreyia »

Thanks for the reply Mike. So if I understand correctly...you're saying the AC button itself MIGHT be defective on the heater function side when you release it for stopping the AC and turning on the heater. Is it possible that the AC button (heater function side) could still work for the AC side but not for the heater function? I will also trace power soon.

Thanks again.

VT
Mike W.
Posts: 26872
Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: New Heater Blower, new fuses, still no work

Post by Mike W. »

It's a switch, I don't know why it couldn't fail on the heat side. I've never had one open so I don't know what it looks like inside.
matreyia
Posts: 64
Joined: Dec 22, 2021 1:05 AM
Location: Houston

Re: New Heater Blower, new fuses, still no work

Post by matreyia »

You were totally correct. I replaced the blower, the relay to zero effect. Once a brand new button (holy crap they are expensive new...like $140) was installed, the heater blower fired up with no hesitation when set on heat.

When I look at the old button, it appears someone tried to opened it and fix whatever they thought they could fix... which was NOT in their list of talents. The previous owner literally rigged every single thing that went out on this car...so when I got it, it was full of horrible ghetto extras like an autozone horn button with wires running out the window into the hood, a auxiliary fan switch velcroed on the carpet in the driver area with telephone wire running to the aux fan cut onto the power wire on the stock AC compressor..and so much more. Now it's all back to stock and all electrical is working, zero lights... feels great. Next step is body work.
Will post my youtube videos of the progression when I am done.

Thanks for the help.

VT
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