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Join Date: Oct 2006
Location: MYR S.C.
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auto heat- foot well blowers part deux.

I may have to rename this part tres or the readers digest version for the older group.
16volt did an awesome job in the link below. way more detail than mine

The No-Heat 930 - Questions

so i have dug into the auto heat while waiting on backing plates to be powder coated so i can finish the wheel bearings.
this is kind of a a part2 of this thread.

Help with 930 Heating Problem (Footwell Blowers)

thanks to the guy that sent me the good diagrams.

the foot well fans DO NOT run all the time!!
mine did, perhaps due to the fan switch going bad.

some terms:
NC-normally closed contacts
NO-normally open contacts
SW-switch
AH-auto heat.

removing the AH:
i removed the passengers seat to get to the right side of the AH to remove the linkage for the flappers. you may be able to remove it from the parking brake hole without removing the seats.
i had to weld my allen to one of the bolts for the seats. they will strip out and they are tight. i ended up taking both seats out for other work along with cleaning the carpet.
taking the AH apart is pretty straight forward.

this is the control part of the AH. the SW at 7 oclock is the one that activates the motor to open the flappers. this SW is NOT on the diagram
the SW at 12 oclock is for HI. the 5 oclock SW is for med fan speed. this one is only active for 2 positions.


now to the meat of the system and probably what fails the most.
the SW with the red and blk wires provides power for low and med fan speed along with power to hi speed fan relay. the SW below it is the limit SW for the flapper controls. they both are activated at the same time. so as soon as the flappers are open the fan comes on. these 2 switches are the SAME!!! the limit SW uses the NC contacts and the fan speed SW uses the NO contacts. so guess what, since i am not rich(and cant afford $70 for ONE jack stand) i combined both functions on one SW.


here i have moved one wire to the other SW and have tinned the other contact for the other wire.


both wires soldered and heat shrink installed.


last note:
these are 5a 250v switches. part number on the sw was 83 133.
i measured about 2.3 amps thru the SW with both fans on low.
FYI one fan pulls about 2.3 amps on hi, BUT there is a separate relay for hi speed.
you can do the fix i did but who knows how long it will last. maybe there was a reason for why 2 switches were used.
i put the SW in use on top so i could use the adjusting screw to adjust the limit.
these switches seemed pretty cheap and i was kind of surprised they are used to run 2 fans.


flappers:
it took a lot for me to move the lever for the flappers, even after cleaning them up.
i removed the cable housings and cleaned the insides and put a little grease on the cable. i also made sure the flappers worked easily.
__________________
86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:

Last edited by T77911S; 01-03-2017 at 09:24 AM..
Old 01-01-2017, 02:03 PM
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just a quick note on how this works without getting into too much detail.
the SW at the top that has 12v going to it and is closed is the SW that goes bad.
as you can see it provides power to the low speed resistors, the hi speed relay coil and to the med speed SW.
the SW with the green line just provides the ground from the hi speed relay to turn it on.
the circuit board does control the motor that opens the flappers. i dont know much more about it other than i suspect that it monitors the cabin temp and will turn the heat on or off as needed.
this is just a guess. there is no changing the air temp of the heat since the flappers are either open or closed.
there is a temp sensor in the dash with a little motor that pulls air in.
there is also a temp sensor on the flapper, why i could not tell you.
the system will work with both temp sensor disconnected.
if the fan ONLY works on hi, either the resistor network on the passengers floorboard is bad on the fan SW in the AH is bad.
pull the connector on the resistor network, with the AH on, use a test light and check for power at the connector to the resistors. if you have power, the resistors are bad, no power, you are taking the AH apart.
you can also pull the connectors off of the fans. power at the fan and you are pulling the fans out.
no hi speed, check the relay. i always assume you have checked the fuses. give them a twist.



__________________
86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:

Last edited by T77911S; 01-01-2017 at 03:05 PM..
Old 01-01-2017, 02:04 PM
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on to the fans.
these seem to be pretty good fans, much better than some of the others i think.

remove the fan, remove the back cover, one screw, remove the connector.
then you can lift the spring off the brush and remove it. as you can see the the first pic the rotor is pretty burned on mine. i was not sure how i was going to fix this since the motors do not come apart.
i cut a small strip of sandpaper and stuck it in the hole for the brush. then turning the motor i got the paper to go into the motor. then with s screwdriver i pushed down on the paper while turning the rotor. it cleaned up very nice.
you can pull the motor out. just mark the motor in relation to the plastic housing so it goes back in the right way.
once i did all this my motors were quiet and working great.



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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:

Last edited by T77911S; 01-01-2017 at 02:55 PM..
Old 01-01-2017, 02:06 PM
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i always wonder why people post blurry pics, my vertigo had kicked in at this point and i was using my phone and did not verify they came out clear.
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 01-01-2017, 03:07 PM
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thanks for posting this for posterity. I had issues with my auto heat as far as back as 2002 and did something similar but I'll be damned if I can recall it now. Should have documented it right here like you just did.
I hate how I can spool up on an issue and eventually have almost zero recollection of it... I'm left with just a vague sense of once knowing a lot more than I do about the item. Like Charlie in "Flowers for Algernon", or coming across your college physics notes.
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Old 01-01-2017, 04:00 PM
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I fiddled with the auto heat around 10 years ago so the fans would come on right away rather than a couple minutes later that seemed like forever after the stepper motor s l o w l y pulled the diverter valves open.
Can't remember what I did now but do remember the micro switches for the footwell blower fans.
Old 01-01-2017, 08:45 PM
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I am not sure how you could do that. Perhaps the limit SW that is b used when you turn the heat off has a set of contacts that are NC. That way as soon as the arm comes off the SW the fans come on. Just a guess though.
I considered a way to bypass the circuit board thinking it might be a hard/expensive part to get. But I am guessing the fan SW is the hi failure item.

The link above did list a part and supplier for the SW.
my fix could shorten the life of the other SW.
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 01-02-2017, 07:43 AM
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Here is my investigation/dissection/repair thread on Autoheat.

The No-Heat 930 - Questions

I have all the switch positions and settings mapped out.
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Old 01-02-2017, 08:07 AM
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I remember the stepper motor driven wheel that slowly turns and pulls the cables that open the diverter valves. That wheel or whatever you call it has a raised edge like a cam at the end of it's rotation that trips one of those micro switches when it has turned all the way and finished pulling the diverter valve cables as far as they will go.

I tripped the micro switch with my finger to find out what it does and when the foot well blowers came on by doing that I liked it and probably connected the two wires on that micro switch together so the foot well blower fans would come on right away when turning on the auto heat dial. They still have two or three rotation speeds while turning the 1987 version autoheat knob that has 10 positions on it.

In the 1" thick folder of work order receipts I got with my car I found one where the previous owner had the auto heat unit replaced a year or two before I got the car for around $1000 so it was still working well and I think it still does.
We havn't had any cold weather yet this winter in S. Florida so we'll see.
I can relate to your vertigo . . .
Old 01-02-2017, 09:08 AM
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Thanks for posting this T77911S!


Quote:
Originally Posted by gsxrken View Post
....
I hate how I can spool up on an issue and eventually have almost zero recollection of it... I'm left with just a vague sense of once knowing a lot more than I do about the item. Like Charlie in "Flowers for Algernon", or coming across your college physics notes.
Amen brother!!
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Old 01-09-2017, 09:02 AM
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any ideas on which wires he is using to power servo motor

https://www.youtube.com/watch?v=eh3VgTZC3ws
Old 01-17-2018, 06:52 AM
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