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Thread: Heater valve test and questions
07-26-2006 10:32 AM #1
Heater valve test and questions
Posted: 26 Jul 2006 14:30 Post subject: Heater valve test and questions
I am back to restoring the interior and have gotten to my AC and Heating section. I have replaced everything since my heater core leaked. Before I tackle my AC problem, which is compressor doesnt turn on when I hit the AC button, but I can jump it directly and it works, I want to make sure my heater is working. Besides changing out my heater core, I changed out diaphram in the heater valve, temp control knob, heater core sensor. I had tested the knob before and it was getting erractic voltage to the heater valve. I swapped out the piece with one my father had in the garage. I do notice voltage changes if my is completely turned on versus just the key turned. The way the heater valve works is that when it gets full voltage, it closed the valve and no water goes into the heater core. When I turn the knob over to the coldest setting, I get +13v. I keep getting the same reading until finally I move the knob over to about 3 o'clock positon, when it start to fluctuate between the +13v and 0.07v. And when I place it to the hottest setting, it stays at 0.07v. This seems ok but being that it is not 0v and 0.07v I just want to make sure its ok. The bentley just has a voltage test against the knob, but no real test for the knob itself. I still have to check my interior temp sensor and heater core temp sensor. The heater core temp sensor is new and I have tested both for resistance, but this time I want to compare it to a thermometer, which I forgot to bring it yesterday to the garage.
I want to make the water is flowing correctly. I believe of the 2 hoses coming to and from the heater core, the top one is the return to the engine and the bottom one comes for the heater valve. I used the parts diagram and parts nameing for this. I guess I can try disconnecting the hose and add another hose to see if water flows accordingly. Does this sound good? I try to touch it, but the engine heats up everything in the engine bay so I can't get a good assumption. Before 2yrs ago when I had the car running I would notice heat when AC was on, which would had made sense since the knob would keep the valve open at all times, but the diaphram rubber was damaged. I ran the heater last friday. I opened the top and lower vents and with a thermoter, i got + 120 degrees right at the lower vent. Outside it was +90. So I know the heater is working just want to make sure it works automatically, becasue when I lowered the temp on the knob, I would get no change, maybe becasue of the sensors or because its running the heater valve open all the time. I might have to test this during a cooler time, maybe at night.
My father sold his 2 e28's so I have nothing to compare it too. If anybody is in my area, Miami, FL, I can bring my multimeter over to take some readings, I would appreciate it.
Any help or ideas will be greatly appreciated.
07-27-2006 08:47 AM #2
this may help
I think that show the hose location according to it's shape.
As far as the voltage, this is a simple on off valve that is controlled based on the heater core temp and the car's interior temp.
Look at the ETM page 6411 to see the module that controls it.
look for AC control section
I think that using a test light on the valve will be better than a multi meter. will give you a better sense of On and Off without trying to undersand fractions of a volt. These older cars are pretty safe to probe around with a test light.
07-27-2006 09:35 AM #3
Re: this may help
Using the diagram is how I came up with my guess for the hose. But the actual shapes versus the diagram are a little different. I thing my guess is right, but only way to find out is unpluging the hose.
I will test the modules, but didnt have my thermometer at the time. But I use the the test light. Maybe the on and off like you said is good enough.
Would you know if the orientatino of the connector matters? The connector has a specific groove but fits both ways on the valve itself. I know the wires are different but not sure if one is + vs the other -.
07-28-2006 10:07 AM #4
07-28-2006 12:53 PM #5
Re: If you can wait a couple of days..
thanks so much. I totally forgot that i had a copy of the bmw workshop manual for the m6. So I looked at the heating section and has a huge troubleshooting procedure for the heater. Will follow them this weekend. Even shows the diagram of the water flow thru the valve. Just doesnt have orientation of plug, which might not matter, but want to be sure. So I will be testing all the sensors against a thermometer, testing the electical side of the valve. It said you use a test light like you said. It uses 4 second intervals. So as long as my sensors are fine, i will see if my temp control is working fine.
07-28-2006 02:44 PM #6
07-29-2006 05:55 PM #7
here is an update
Ok, here is an update of today. I checked out using a test lamp to test the temp knob, and everything is fine. I get the 4 second delay. Also the heater core temp sensor is fine. The interior temp sensor works but not correctly. It is off by 10 degrees. Will get one this week. Either I order a new one or find a good used one. Any idea on price? The next test is to look at heater valve. The insert part is brand new. I dont get any thump or feel any vibration when i would hit the control knob. The bmw manual say to jump it directly. I tried that and nothing either. Here is the question, even if i change the insert, can it still not work? Maybe the electrical side is bad or corroded. Do you know if I can by the casing with out the insert?
08-02-2006 07:11 PM #8
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08-03-2006 09:34 AM #9
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