Need help - no heat

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E24Julian

Need help - no heat

Post by E24Julian »

The blower in my 87 635CSi only works when the AC is on, so I have no heat, defrost or anything - my only choice is cold air. Can anyone give me some advice?
Chris Wright

Re: Need help - no heat

Post by Chris Wright »

E24Julian wrote:The blower in my 87 635CSi only works when the AC is on, so I have no heat, defrost or anything - my only choice is cold air. Can anyone give me some advice?
There are two blowers up front**, one for the Heating/Ventilation and one for the A/C, so we need some more Info to help (**there is a third blower in the back if you have the rear A/C unit, this write-up ignores the unit in the back):

First thing, check fuses 19 and 20.

There are 3 transistors, one at the heater blower and one at the A/C blower and one in the Blower Speed Control knob in the dash itself.

To troubleshoot what is wrong:
With the key in the run position, turn the Blower Speed Control knob clockwise. The heater blower should run at variable speeds until it reaches the max position at which point a micro-switch is depressed that routes full voltage direct to the blower.

Rotate the Blower Speed Control knob back counter-clockwise. Now push the A/C button and turn the Blower Speed Control knob clockwise again and see if the A/C blower runs variable until it reaches the max position and runs on high.

1) If the heater blower only runs on high in the full Max position and the A/C runs normal, then the heater blower transistor is bad.

Here is removing the heater blower and replacing the heater blower transistor (with lots of pics!):
http://www.normgrills.net/bcg/Blower_Transistor.htm
____

2) If the A/C blower only runs on high and the heater runs normal, then the A/C blower transistor is bad.

Here is replacing the transistor for the A/C blower without removing the blower:
http://www.malloc.nl/BMW/635CSi/pages/e ... l#refertoc

Caution: You must remember to disconnect the battery before removing the impact switch in step 3 in the workshop manual or you run the risk of burning out the switch! (They have a caution in the ETM but not in the Manual, go figure??)
____

3) If both the heater & A/C blowers only run on high, then the Blower Speed Control transistor in the dash is bad.

Here is replacing the transistor in the blower control in the dash:
viewtopic.php?t=2465

_________
Here is the heater blower transistor:
Image
_________


4) If the heater blower doesn't run at all and the A/C blower does, then the heater blower motor may be bad, or the blower select relay may be bad.

5) If the A/C blower doesn't run at all and the heater blower does, then the A/C blower motor may be bad, or the blower select relay may be bad.

6) If both the heater & A/C blower won't run at all, then it is likely the blower select relay or the ground to it, is bad.
___

If the heater blower may be bad, see the link above to remove it and test it on the bench.

The Blower Select Relay is located in the right side of the center console next to the glove box. I believe you have to release the pins on the glove box straps and drop the door to get to it:
http://www.malloc.nl/BMW/635CSi/pages/e ... l#refertoc

It is a 5 prong change-over relay with the output pins of 87 and 87a. Do not confuse it with the 5 prong Main relay with the output pins 87 and 87b, they are not interchangeable. The High-Beam Headlamp (K3), is the same and can be used to swap out and test the Blower Select relay in the Center Console.

Here is a listing of the relays, scroll down to "High-Beam Headlamp (K3), and Blower Select relay in the Center Console:"
viewtopic.php?t=13182&

_________

This diagram is for an '85 so the fuse and some wire numbers are different, but the layout is the same:

If the image doesn't open: http://www.stormpages.com/countchocula1/bmw/etm158.htm
Last edited by Chris Wright on Sun Aug 03, 2014 9:12 pm, edited 5 times in total.
E24Julian

Re: Need help - no heat

Post by E24Julian »

This is really terrific information - thank you very much.
I'll report back what I find.
E24Julian

Update

Post by E24Julian »

Took me a while but as long as the weather was nice I kept prioritizing other issues. It's finally turning cold, so....As it turns out, one of the electrical leads had worked itself loose. Still it was a good opportunity to lube the bushings and vacuum out years of debris. It now works pretty well but makes a weird growling noise at medium to high speeds. I am going to open it up again and re-lube but if anyone has another idea, I'd love to hear it.
horsetan

Post by horsetan »

With regard to the type of replacement transistor ye need, note that the original suggested part has been superseded by others, so ye'll obviously need to find the present-day equivalent.
st6phen

Re: Need help - no heat

Post by st6phen »

Chris Wright wrote:
E24Julian wrote:The blower in my 87 635CSi only works when the AC is on, so I have no heat, defrost or anything - my only choice is cold air. Can anyone give me some advice?
There are two blowers up front**, one for the Heating/Ventilation and one for the A/C, so we need some more Info to help (**there is a third blower in the back if you have the rear A/C unit, this write-up ignores the unit in the back):

First thing, check fuses 19 and 20.

There are 3 transistors, one at the heater blower and one at the A/C blower and one in the Blower Speed Control knob in the dash itself.

To troubleshoot what is wrong:
With the key in the run position, turn the Blower Speed Control knob clockwise. The heater blower should run at variable speeds until it reaches the max position at which point a micro-switch is depressed that routes full voltage direct to the blower. Rotate the Blower Speed Control knob back counter-clockwise. Now push the A/C button and turn the Blower Speed Control knob clockwise again and see if the A/C blower runs variable until it reaches the max position and runs on high.

1) If the heater blower only runs on high in the full Max position and the A/C runs normal, then the heater blower transistor is bad.

2) If the A/C blower only runs on high and the heater runs normal, then the A/C blower transistor is bad.

3) If both the heater & A/C blowers only run on high, then the Blower Speed Control transistor in the dash is bad.

Here is removing the heater blower and replacing the heater blower transistor (with lots of pics!):
http://www.normgrills.net/bcg/Blower_Transistor.htm
_________
Image
_________

Here is replacing the transistor in the blower control in the dash:
viewtopic.php?t=2465

___

4) If the heater blower doesn't run at all and the A/C blower does, then the heater blower motor may be bad, or the blower select relay may be bad.

5) If the A/C blower doesn't run at all and the heater blower does, then the A/C blower motor may be bad, or the blower select relay may be bad.

6) If both the heater & A/C blower won't run at all, then it is likely the blower select relay or the ground to it, is bad.
___

If the heater blower may be bad, see the link above to remove it and test it on the bench.

The Blower Select Relay is located in the right side of the center console next to the glove box. I believe you have to release the pins on the glove box straps and drop the door to get to it?

It is a 5 prong change-over relay with the output pins of 87 and 87a. Do not confuse it with the 5 prong Main relay with the output pins 87 and 87b, they are not interchangeable. The High-Beam Headlamp (K3), is the same and can be used to swap out and test the Blower Select relay in the Center Console.

Here is a listing of the relays, scroll down to "High-Beam Headlamp (K3), and Blower Select relay in the Center Console:"
viewtopic.php?t=13182&

_________

This diagram is for an '85 so the fuse and some wire numbers are different, but the layout is the same:

If the image doesn't open: http://www.stormpages.com/countchocula1/bmw/etm158.htm
just completed replacement of the heater blower transistor. Has to be one of the most satisfying fixes ive done to date. superb post and easy fix.
matthewdesigns
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Re: Need help - no heat

Post by matthewdesigns »

OK so yeah this thread is pretty old, but instead of starting a new one to hash out some of the same stuff I'm necromancing it...

I have a scenario similar to combo #4 listed above: A/C blower operates (but only on High), and zero response from the heater blower. I'm trying to save myself from blindly throwing parts at the problem. Based on the way the 2 motors are/aren't working I'm thinking that the dash control needs the transistor repair at the very least (since the A/C only works on High), so I'll likely start there. But that probably won't resurrect my heater motor.

Over the weekend I tried jumping the heater blower with 12V directly to the two connections on the front of the motor and got no response. My immediate thought was of course that the motor or brushes are bad. However after reading a number of threads related to blower motor issues it seems that merely jumping it may not yield a response; that does not make sense to me but if someone can back up that info I'd appreciate it.

If jumping the heater motor directly *should* yield a response then I'll guess that the brushes/motor are bad and will address that; if not I'll replace the heater blower transistor. I see that there is a blower selector relay but I'm not yet convinced that there's a problem with that, and likely can't say for sure until the heater blower is operational.

Any additional insight will be greatly appreciated.
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Re: Need help - no heat

Post by baders »

Matthew, put your car details in your signature. It helps us diagnose.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
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Re: Need help - no heat

Post by matthewdesigns »

baders wrote: Thu Aug 31, 2017 1:20 am Matthew, put your car details in your signature. It helps us diagnose.
Thank you for the reminder, baders!
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Re: Need help - no heat

Post by baders »

matthewdesigns wrote: Wed Aug 30, 2017 2:28 pm OK so yeah this thread is pretty old, but instead of starting a new one to hash out some of the same stuff I'm necromancing it...

I have a scenario similar to combo #4 listed above: A/C blower operates (but only on High), and zero response from the heater blower. I'm trying to save myself from blindly throwing parts at the problem. Based on the way the 2 motors are/aren't working I'm thinking that the dash control needs the transistor repair at the very least (since the A/C only works on High), so I'll likely start there. But that probably won't resurrect my heater motor.

Over the weekend I tried jumping the heater blower with 12V directly to the two connections on the front of the motor and got no response. My immediate thought was of course that the motor or brushes are bad. However after reading a number of threads related to blower motor issues it seems that merely jumping it may not yield a response; that does not make sense to me but if someone can back up that info I'd appreciate it.

If jumping the heater motor directly *should* yield a response then I'll guess that the brushes/motor are bad and will address that; if not I'll replace the heater blower transistor. I see that there is a blower selector relay but I'm not yet convinced that there's a problem with that, and likely can't say for sure until the heater blower is operational.

Any additional insight will be greatly appreciated.
OK thanks. My first question is, do you have the Electrical Troubleshooting Manual and a multimeter ?

There should be no reason why jumping 12v to the motor should not work. The Blower Select Relay does need to be de-energised for this test to work however. To properly test this, simply bridge the Blower Select Relay or just connect the Brown/Red on the heater blower motor to ground and then jump 12v to the blue black. That said, most problems with this system involve the transistors.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
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Re: Need help - no heat

Post by matthewdesigns »

Thank you.

Yes, I do have both the manual and a multimeter. I will test the motor as described and see what happens...perhaps I did not have a secure enough connection on one or the other terminals on the motor the first time I tried this.

I did verify incoming voltage at the two leads that connect to the motor, and by turning the speed control on the dash I see zero and 12V or a little more, but nothing in between. This is part of what lead me to guess that the control panel transistor is bad, as my understanding is that I should see a sweep of voltage at the motor while turning the speed control.
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Re: Need help - no heat

Post by baders »

matthewdesigns wrote: Thu Aug 31, 2017 2:15 pm Thank you.

Yes, I do have both the manual and a multimeter. I will test the motor as described and see what happens...perhaps I did not have a secure enough connection on one or the other terminals on the motor the first time I tried this.

I did verify incoming voltage at the two leads that connect to the motor, and by turning the speed control on the dash I see zero and 12V or a little more, but nothing in between. This is part of what lead me to guess that the control panel transistor is bad, as my understanding is that I should see a sweep of voltage at the motor while turning the speed control.
But is the motor operating at all ? If you are saying that there is 12v measured across the motor then it should be working. If it is not, then the motor has a problem. Not to say that there is not a problem with transistors either.

The Blower Speed Control inputs a variable signal to the base on the heater and A/C transistors. At max blower speed, it is bridged out and the full 12v is applied. Basically, you are using a smaller variable voltage (and thereby current) to control a larger one (blower motors). I did a nice little diagram describing this on the forum but can't find it now.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
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Re: Need help - no heat

Post by matthewdesigns »

The heater motor is not operating at all even with 12V present via the normal harness connection. The A/C motor operates at high speed only, and only when the A/C switch is depressed.

I checked voltage at the heater motor and saw only 12V when the speed control was moved...not a variable range.

Seems to me this means the motor is bad, needs brushes, etc, and that the controller in the cabin needs the transistor repair.

But I'm just learning the ins/outs of this complex beast so I don't want to jump to conclusions O:)
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Re: Need help - no heat

Post by kxlara »

Quick question on the old thread. my heater blower is dead, I have the cover off. should I be able to spin it by hand and if not, is that a solid sign that I just need to buy a new motor? it doesn't look great.

Thanks!
Chris
1987 635CSI
Chris Lara

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Re: Need help - no heat

Post by hornhospital »

If it doesn't spin freely by hand, it's probably toast. You can try rehabing it by lubing the bearings, but keep your eyes open for a replacement.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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Re: Need help - no heat

Post by BenM635i »

Just bought a new Bosch motor for the blower from a company on your side of the pond.

Not arrived yet but at ~$90 it seemed like a good idea to replace mine after 35 years use. Regularly oil mine however it still isn’t as free as could be.

Apparently it’s not a bad swap as long as you take care when swapping the fins from the old to the new.

Company sells via eBay and for you guys in the states then I think it’s a bargain.. even with shipping and duties to the UK it’s still a third the price of a complete new assembly.
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Re: Need help - no heat

Post by northNH »

'86 635 5spd 175K Blk/blk orig paint/int
‘88 M6 24K time capsule Black/gray
'92 MBz 300CE Sportlined 175K Blk/wine orig paint/int
‘94 MBz E320 wagon
'62 Volvo Amazon 65K mile time capsule

One lucky guy...
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