Posted: 26 Jul 2006 14:30 Post subject: Heater valve test and questions


Hey everybody,

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.

88 m5
91 318is
04 civic