Aux fan running all the time

[Sowhatsg]

Hello,
On my 1983 E24, the aux fan is running even when contact is off. I have to disconneçt battery or remove fuse 3 to stop it.
I swapped relays K1 and K6 and it’s the same, so relay K1 is likely good.
Using 633CSi electrical debugging manual, I disconnected C106(between compressor clutch and pressure cutoff), that stops fan.
Diagnosis seems to indicate there’s power to input 86 of relay K1 all the time. On diagram, can’t see where it could be coming from.

Any suggestion or further check that would be useful?

Compressor has been replaced with dryer bottle and now air con is running fine. Aux fan runs since the repair, didn’t do that when dead compressor was in and R12 circuit was empty. Now running R134 gas BTW.

Thanks

[jbd5015]

http://wedophones.com/Manuals/BMW/19...g%20Manual.pdf

Here is an online pdf of the trouble shooting manual with wiring diagrams that might help.

Under normal circumstances, 86 will only get power through the energized relay. You may have a melted wire causing a short to power on the circuit under the fuse box.

Id also double check the temp switches on the radiator to make sure they havent failed in the closed position.

K5 unloader relay might also be a suspect...

[Sowhatsg]

Good ideas, thanks for the prompt response. Will check into it next week.

[carsnplanes]

If the Aux fan is on low speed, and I am assuming it is, it can be turned on two ways, when activating the AC switch to ON...or when the "Normal speed coolant sensor" on the radiator is activated (Ign has to be on for that) through the K1 Normal speed relay. If the fan is on "high speed", then the only way it can be activated is by the radiator's high temp sensor which energizes the High Speed relay.
Unplug the Normal speed relay K1. Does the fan stop? Probe the compressor clutch connector. Is there 12V there? If so, then there is an AC command being given to both the relay and the clutch. If no 12V at the clutch connector, then assume it's coming from the "Normal speed temp sensor" command. Normal speed fan power supply is from the Ign power, so should not be supplying any power from there. Assume K1 relay is stuck closed passing HOT 12V to the aux fan.AC 1.JPGAC.JPG

[carsnplanes]

Attachment 703300

[Sowhatsg]

Yes, it’s the low speed fan. When K1 is unplugged, fan stops. The wiring drawing I have is different from yours, mine is from the 633CSi pdf.
When C106 and C105 unplugged, K1 in place and battery connected, ignition off, there is power at C106 on the high pressure cutout side.
I need to check upstream of high pressure cutout.

will also check under fuses but not sure how delicate it is to remove top part of fuses box??

30796452[/URL]]


If the Aux fan is on low speed, and I am assuming it is, it can be turned on two ways, when activating the AC switch to ON...or when the "Normal speed coolant sensor" on the radiator is activated (Ign has to be on for that) through the K1 Normal speed relay. If the fan is on "high speed", then the only way it can be activated is by the radiator's high temp sensor which energizes the High Speed relay.
Unplug the Normal speed relay K1. Does the fan stop? Probe the compressor clutch connector. Is there 12V there? If so, then there is an AC command being given to both the relay and the clutch. If no 12V at the clutch connector, then assume it's coming from the "Normal speed temp sensor" command. Normal speed fan power supply is from the Ign power, so should not be supplying any power from there. Assume K1 relay is stuck closed passing HOT 12V to the aux fan.AC 1.JPGAC.JPG

[carsnplanes]

Yes, it’s the low speed fan. When K1 is unplugged, fan stops. The wiring drawing I have is different from yours, mine is from the 633CSi pdf.
When C106 and C105 unplugged, K1 in place and battery connected, ignition off, there is power at C106 on the high pressure cutout side.
I need to check upstream of high pressure cutout.

will also check under fuses but not sure how delicate it is to remove top part of fuses box??

Yes, I knew you had a 633. I didn't have a 633 diagram but figured it would be close enough as far as the command to turn on the aux fan in Normal speed. Yes removing the K1 relay would certainly remove the control to the relay as well as the HOT wire path to the fan motor through it. So if there is power at C106, that means there is also power at the compressor clutch(is it being pulled?) and also at terminal 86 of the K1 relay, which would pull it. This would of course allow 12V bat power to pass and power the aux fan motor.
Does your diagram also show the normal speed temp sensor providing ignition power to the K1 relay as well?. You can see, at least in my 635 WD, that there is a diode that is supposed to direct incoming 12V from both the AC command and the temp sensor command to the K1 relay when aux fan is needed.
Do you have a diagram of your 633 AC system? In the 635, the C106 line to the High pressure cut-out path to the compressor clutch shouldn't be getting bat HOT 12V from anywhere. Only low current AC command signal from the AC controller.

[Sowhatsg]

The post from jbd5015 above has a link to the 633CSi diagram. It’s on page 58 of 82, chapter 148. Well I assume mine is the same even if it’s a 628, not a 633.
I can’t see any source of power outside the 30 on the K1 relay. Does this confirm, like jbd5015 was suggesting, that there is possibly a short circuit under the fuse box that provides power to 86, therefore, C105 and C106 and aux fan all the time?
Next week, I will look into it.
Appreciate the help of users, I am not very literate in car electrics or mechanic…

[carsnplanes]

The post from jbd5015 above has a link to the 633CSi diagram. It’s on page 58 of 82, chapter 148. Well I assume mine is the same even if it’s a 628, not a 633.
I can’t see any source of power outside the 30 on the K1 relay. Does this confirm, like jbd5015 was suggesting, that there is possibly a short circuit under the fuse box that provides power to 86, therefore, C105 and C106 and aux fan all the time?
Next week, I will look into it.
Appreciate the help of users, I am not very literate in car electrics or mechanic…

So, thank you Jeff for the 633 ETM link. Yes so it seems your circuit is slightly different in that there are two separate paths to your aux fan. One from the energized K1 relay(energized by the AC ON command, which would power the compressor clutch too), and the other path from the Normal speed temp sensor in the "made" condition, but only with ign on. The only BAT HOT path runs through the energized K1 relay. Note: the AC switch is the trigger for the Aux fan, so even if there is no freon in the system, just having the AC switch in the ON position, will power the aux fan by energizing the K1 relay.
Also ensure your K1 relay is a 4 prong relay, and not 5.
633 aux fan.JPG

[Sowhatsg]

Yes, K1 is a 4 prong relay. I swapped K1 with K6 and even K5, behavior does not change. Will do more checks this afternoon. Fuse box does not seem easy to remove. After removing screw and bolt, trying to pull it up, but don't want to break anything. Other thing is that fan stops when relay is removed, so it seems there is no current flowing from 30 to 86 in relay lodging when K1 is out.
Have hard time removing connector on high pressure cutout. Not the one on the dryer side, but upstream, the white connector going to dryer.
BTW, fixed the variator on fan speed. Replaced transistor located next to squirrel cage, cleaned the circuit and connectors, replaced the crumbled foam on the steel plate. Now have 4 speeds !!

[carsnplanes]

Yes, K1 is a 4 prong relay. I swapped K1 with K6 and even K5, behavior does not change. Will do more checks this afternoon. Fuse box does not seem easy to remove. After removing screw and bolt, trying to pull it up, but don't want to break anything. Other thing is that fan stops when relay is removed, so it seems there is no current flowing from 30 to 86 in relay lodging when K1 is out.
Have hard time removing connector on high pressure cutout. Not the one on the dryer side, but upstream, the white connector going to dryer.
BTW, fixed the variator on fan speed. Replaced transistor located next to squirrel cage, cleaned the circuit and connectors, replaced the crumbled foam on the steel plate. Now have 4 speeds !!

Ok, so yes, you would expect to lose everything when you remove the K1 relay, but you could be also losing the control as well as the power path to the fan. Let's not dismiss the fact that there could still be an un-requested command from somewhere pulling the relay. Have you swapped or tested the suspected K1 relay to see if the 30-87 path in that relay is maternally stuck closed providing a 12Volt HOT path to the fan? So Just re-read you account, (sorry I missed that), that you said another known good replacement relay makes it behave the same. That means something is continuously pulling the relay with ign off. Can you see if 86 is hot when it's not supposed to be? It's the only wire terminal on the base that would pull the relay.

Very strange indeed. Can you pull of the connector to the high pressure cut-off switch and see which pin side is powered all the time? Trying to figure out which side power is coming in from to power 86 of the K1 relay.
K1 633.JPG

[Sowhatsg]

Well, we did quite a bit of voltage measurements yesterday and I can't make any sense out of it. I am also wondering if the wiring diagram is the 633CSi or the 635 you sent earlier...One of the differences is the compressor clutch diode that does not exist on the 633.
Anyway, here are the data. Only the battery + is connected, we connected the - at some steps to check if the aux fan would start or not based on what is plugged/unplugged.
When C106 or high pressure cutout(HPC) are disconnected, the aux fan does not run.However, there is 12.2 V on the HPC, black&white(B&W) side , 0 V on the black side. We think the B&W side is the Y to/from 86 on K1 and C105 from compressor control.
We also disconnected C105 and with HPC and C106 disconnected, there is 12.2V on C105 B&W, 10.5V on C106 compressor clutch side and 12.2V on HPC B&W. Fan does not run.
With the above disconnected and white connector coming from clutch disconnected, there is 12.2V on HPC B&W, 10.5V on C106 compressor clutch side, 10.5V on one side and 10V on the other side of this connector.
IMG_0465.jpg
On the left of the picture, you can see a small piece of the brown wire coming from the clutch and going into the black "housing". Out of this housing, one wire going to C106 and the other one to the white connector. There is a big wire on the other side of the connector that is going back to the clutch.
As I am writing this, it seems I am answering yes to your question on #4, meaning there seems to be an AC command given to the relay and the clutch.
I have more measurements with various combinations of plugged/unplugged, but I am not sure it's useful to list them all.

[carsnplanes]

Any update to this ? Curious what you have found..if anything.