e12 based hvac question (fan control)

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Carlp336
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Location: Winston Salem NC

e12 based hvac question (fan control)

Post by Carlp336 »

for those with early cars. i recently swapped out transistors and the outer blower motor for new..

i noticed something ive not before on reassembly and testing.
the lower blower motor in the console is always on (low speed) when i key is on, even if the left : "heat - O - cool" dial is set to O.

is that correct ?

if i turn to warm it shuts off for the other.
.1977 H&B 630CSI - http://www.sidedraftsix.com.
Dmckim
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Re: e12 based hvac question (fan control)

Post by Dmckim »

It shouldn't. Sounds like it is still getting a current draw through that switch. What exactly did you replace?

Dale
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Carlp336
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Re: e12 based hvac question (fan control)

Post by Carlp336 »

Dmckim wrote: Tue Mar 19, 2019 1:11 am It shouldn't. Sounds like it is still getting a current draw through that switch. What exactly did you replace?

Dale
Buffalo, NY
replaced both transistors and the heater blower..

seams as if when the dial is set to O the ac blower is running, only off when turned to hear
.1977 H&B 630CSI - http://www.sidedraftsix.com.
bpoliakoff
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Re: e12 based hvac question (fan control)

Post by bpoliakoff »

Carl I am having problems with the circuit board for my fan rheostat as we speak affecting fan speed being on and off. I have gone through all the spares I have and can't find a good one. It never ceases. Biggest problem I am having with mine is it wasn't factory air and we are putting all the controls for factory air in and have pulled all the after market things out. When I tore the car down many years ago, I pulled an after market loom for the add on A/C out that literally was balled up behind the glove compartment as big as a tennis ball. There was a rheostat of some sort in the glove compartment and I think that was what was used for the fan control. I never used the A/C as I tore the car down 3 days after I brought it home. At least after 10 years it is running and hopefully will be drivable by the end of summer. Again, we are 100% sure it is the circuit board as my problem.
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janusz200
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Re: e12 based hvac question (fan control)

Post by janusz200 »

I'm rather sure that A/C blower does not work when temp.selector is on 0 or turned on red area. But I'll check carefully abd let you know when I got my car back from garage.
Once I found on this forum A/C wiring diagram for '79 model - see attached. Maybe there's some plug mistake and specialist will find the problem having diagram. Good luck.
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Air Conditioner 1979-LHD & RHD-#01.JPG
Air Conditioner 1979-LHD & RHD-#01.JPG (868.45 KiB) Viewed 8119 times
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Air Conditioner 1979-LHD & RHD-#02.JPG (280.64 KiB) Viewed 8119 times
1980 635 CSi EU
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Carlp336
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Re: e12 based hvac question (fan control)

Post by Carlp336 »

janusz200 wrote: Tue Mar 19, 2019 8:57 am I'm rather sure that A/C blower does not work when temp.selector is on 0 or turned on red area. But I'll check carefully abd let you know when I got my car back from garage.
Once I found on this forum A/C wiring diagram for '79 model - see attached. Maybe there's some plug mistake and specialist will find the problem having diagram. Good luck.

thanks please do!

i could be as simple as miss plugged wire when i reassembled. but honestly ive not got enough seat time prior to know if the AC Blower would blow when on "O". i would assume not.
.1977 H&B 630CSI - http://www.sidedraftsix.com.
wkohler
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Re: e12 based hvac question (fan control)

Post by wkohler »

The AC blower should only work when the temp knob is turned from the 0 (0 will still run the heater blower but the heater valve is still closed) to cold/kalt. You should hear the microswitch click. There are two cams on the back of the temp switch. One controls the AC thermostat and the other the microswitch for the blowers.
Carlp336
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Re: e12 based hvac question (fan control)

Post by Carlp336 »

wkohler wrote: Wed Mar 20, 2019 5:02 am The AC blower should only work when the temp knob is turned from the 0 (0 will still run the heater blower but the heater valve is still closed) to cold/kalt. You should hear the microswitch click. There are two cams on the back of the temp switch. One controls the AC thermostat and the other the microswitch for the blowers.
perhaps mine is backwards. ?
.1977 H&B 630CSI - http://www.sidedraftsix.com.
GRNSHRK
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Re: e12 based hvac question (fan control)

Post by GRNSHRK »

Carl, the microswitch is item No. 25 in the diagram above [-o<

IIRC, this switch just completes the ground circuits to either the heater or A/C blower, interesting setup :-?

From what I also recall, neither blower should be actually "blowing" air unless the rotary fan speed dial is turned :-k

HTH \:D/
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Tazzarti
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Re: e12 based hvac question (fan control)

Post by Tazzarti »

Image
https://imgur.com/H5hI4LC

Hi guys, I cant comment on the diagnosis, but this is the diagram from the BMW north america electrical troubleshooting manual. For a 1977 630. Hope this helps.

-Not sure how to embed the photo :S
janusz200
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Re: e12 based hvac question (fan control)

Post by janusz200 »

Carlp336 wrote: Tue Mar 19, 2019 12:59 pm
janusz200 wrote: Tue Mar 19, 2019 8:57 am I'm rather sure that A/C blower does not work when temp.selector is on 0 or turned on red area. .....
thanks please do!
I've checked - A/C blower does not work with selector on 0
1980 635 CSi EU
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biggles
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Re: e12 based hvac question (fan control)

Post by biggles »

I am trouble shooting my HVAC system, and did a complete teardown and cleaned out the core. The main issue I have is that the whole system is dead. No ac or heater fan. Looking at the diagrams I will check the relays first as the fan speed control switch feels good, if the relays are good I will check the switch.
Am I on the right track?
81 BMW 635csi RHD Euro manual.
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biggles
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Re: e12 based hvac question (fan control)

Post by biggles »

biggles wrote: Mon Apr 20, 2020 2:36 pm I am trouble shooting my HVAC system, and did a complete teardown and cleaned out the core. The main issue I have is that the whole system is dead. No ac or heater fan. Looking at the diagrams I will check the relays first as the fan speed control switch feels good, if the relays are good I will check the switch.
Am I on the right track?
So the relays are all functioning correctly and the fan speed control switch is all good. Before I started strippping I checked there was potential accorss the fan fuse in the fuse box. I am now at a bit of a loose end...
81 BMW 635csi RHD Euro manual.
02 M5
02 MCoupe
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