Is there any way to check if the heater control pot. works without removing

[Anton CH.]

Distribution control panel. I would like to hook it up to a ohm-meter and check if the resistance changes as I turn it. Removing the distribution control panel seems like a lot of work.

[talltorontoguy]

What is the issue with your switch? If it's only working on one setting and not on others then its likely not the switch, but rather the "sword".

Rod


Distribution control panel. I would like to hook it up to a ohm-meter and check if the resistance changes as I turn it. Removing the distribution control panel seems like a lot of work.

[Anton CH.]

Rod,
My passenger heat is not working. I don't think my car has a "sword". My guess is that the pot not working. I would really like to hook an ohm-meter up to it and see if it changes the resistance as I rotate the heat switch. I was hoping there was another way to check this as I really don't feel like removing the control panel.

[Unregistered]

Isn't this more likely to be a sticky heater solenoid under the bonnet?

[Anton CH.]

Pretty sure its not the valve, I have a new one installed.

[Bellicose Right Winger]

What happens if you electrically disconnect the heater valve? Do you get full heat on both sides?


Pretty sure its not the valve, I have a new one installed.


Paul Shovestul

[Anton CH.]

Is it supposed to blow warm on both when you disconect it? Doesn't the dial only allow you about 5 degrees of seperation so both would be warm anyway?

[Bellicose Right Winger]

On E28's when you disconnect, heater valve goes wide open. E34's may do the same....if so I'd expect both sides to go full hot, regardless of dial setting. I understood your symptoms are no passenger heat but air flow is fine...is this correct?

Paul Shovestul




Is it supposed to blow warm on both when you disconect it? Doesn't the dial only allow you about 5 degrees of seperation so both would be warm anyway?

[Anton CH.]

Airflow seems fine. I think my aux. water pump might be faulty but that still shouldn't cause it. I'll try it out tonight.

[Bellicose Right Winger]

My understanding is that the aux water pump is needed for low speed driving when engine speeds don't get high enough to ensure water circulation through heater core. If you suspect a faulty aux water pump, then be sure to do your testing at highway speeds or in lower gears to keep engine speed up.

Paul Shovestul



Airflow seems fine. I think my aux. water pump might be faulty but that still shouldn't cause it. I'll try it out tonight.

[John 535is (Sydney)]

On the 535 the plug on the top of the heater solenoids has 3 wires. One each and one common. If you put a meter across two wires you should see the pulses change as you adjust the inside settings. From memory there was something strange like left is right and right is left or something. Anyway, if both pulse its not the switches but the solenoids. You can actually pull these apart, the needle inside has a cone end that seats in the bottom. Apparently that can brake off. I was told by my parts place you can purchase individual parts for these, but as luck has it my solenoids appeared to be faulty so I went with a complete set (both solenoids). Its actually an easy fix, just a bit fiddly getting the unit out with the hoses and wires etc. You kinda have to lift off the threaded studs and push towards the motor, then twist. The aux pump is attached to the bottom and it comes out as one unit.

John 535is 1989

[Bellicose Right Winger]

Anton CH,
Here's a very good description of the E32 heater. I suspect the E34 is similar. Note that there is a stepper motor that controls passenger side temp. There is also a table to let you check resistance of passenger heater core temp sensor. Either of these could be your problem provided you are getting flow thru both heater cores. The bad news is it looks like you need to disassemble the car to get to these parts.

http://bmwe32.student.utwente.nl/
Select IHKA Components on left side

Paul Shovestul

[Anton CH.]

John: I actually have a brand new heater valve installed (broke mine when I tried to clean it).

Bellicrose: Thanks for the link. I actually haven't had the time to disconect the plug from the heater valve to see if it blows both warm. But I have tried turning pasenger heat to max at rpms > 3000, blows cold. However, when I put driver to max, I can notice the temp difference between passenger and driver. So if I remove the plug from the valve I should be able to "feel" if the passenger heater core is working properly. I highly doubt the temp sensor failed, I don't think those things ever fail. For some reason I think its the pot. But will try to test this weekend.

P.S. The stepper motor only opens the flaps correct? There is airflow, so the only reason why I am not getting passenger heat is because there heater valve is closed.

[Bellicose Right Winger]

Anton CH,
I don't know for certain, but from the description "Passenger side temp mixing flap" this sounds like a control that mixes heated air with unheated air to achieve a desired temp. I agree that the heater core temp sensor is unlikely to fail, but it's also relatively easy to check with a DMM....after you get to it that is.
John 535is' procedure to check the outputs to the heater valve is a good one, particularly if it turns out that disconnecting the heater as I suggested results in no heat rather then full heat like E28's.

Paul Shovestul


[QUOTE=P.S. The stepper motor only opens the flaps correct? There is airflow, so the only reason why I am not getting passenger heat is because there heater valve is closed.[/QUOTE]

[Bill R.]

working then I suspect that the hot water is going to take the path of least resistance when splitting off to flow through each side of the heater cores... And one side is getting most of the hot water... I suspect if you reverse the 2 hoses going into the heater cores you'll find that the opposite side gets all the heat... I would fix the known problem of the auxillary pump first.

[Anton CH.]

Ok Bill, that brings me to my next question then. On our cars. Is the aux water pump always on or only when the engine is warm?

[Bill R.]

better system of cataloging, memorys starting to go... Anyway this is for the climate controlled cars but it should be about the same on ours..http://www.bimmernut.com/%7Ebillr/images/auxpumpontimes.jpg




Ok Bill, that brings me to my next question then. On our cars. Is the aux water pump always on or only when the engine is warm?

[Anton CH.]

I guess I was testing the pump wrong (I assumed that it is always on even on cold engine). Can I test it without removing it from it's location?

And I am guessing the Y-factor is resistance value given by the heat control know?

[Bill R.]

Its K8 in the illustration here for the relay, just jumper the relay after checking the fuses to make sure they are good...
http://www.bimmernut.com/%7Ebillr/images/auxpumplocation.jpg
The schematic is here except yours is k8 not k50

http://www.bimmernut.com/%7Ebillr/images/auxpumprelay.jpg















































I guess I was testing the pump wrong (I assumed that it is always on even on cold engine). Can I test it without removing it from it's location?

And I am guessing the Y-factor is resistance value given by the heat control know?