Heater always warm?

[Hypr5]

Hey guys,

a while ago I posted about my AC evaporator getting ICE cold, but only luke-warm, sort-of-cool air coming through the vents. Somebody suggested that maybe a valve was staying open keeping the heatercore always warm.

Well - I never checked it because I haven't been driving the car. Tonight was a fairly cool night, however and I was driving with the fan off, but the dials set to 64 degrees and warm.. almost HOT air was coming from the vents. When I turned on the blower, it did cool down, but not much at all. When the blower was shut back off, it warmed up again. (AC was never switched on)

Is this an indicator of a stuck valve or something? How can I check for it without draining coolant, etc. Would it be easier to just disconnect the heater core and loop back around for the summer time?

Thanks for any input you guys can offer!

[shogun]

Either the valves are stuck, or they do not get power. Without power the valves are full open.
If you checked that the heater valves are working properly it is still possible that the valves open because either there is no 12V at the center pin (of the three pins above the heater valve assembly), or the other two pins don't go to ground (zero volt, measured between the pin and chassis ground).
I am not sure which fuse # these valves have on the E34, Check that one out too.

[JonE]

I think it would be easiest to do what shogun recommends first, also, if power to valves but still sticking, some have tapped the tops of the valves with a hammer to get them moving. Otherwise, some have done the water valve/heater core bypass. Good luck.

[Hypr5]

Alright, thanks guys.

I'll definately check that out. But in the meantime, is what I described even a symptom of a sticky valve or is that normal?

[Jeff N.]

The inner seals begin to fail leading to water in the solenoid units. Once this starts, the plungers stick causing full on or off on of the heat. Usually a sign that the HCV is on its way out. It's a pretty common failure on these cars; no way to R&R the HCV. New one is about $150 or so, pretty easy swap as it's right on top of the engine box.

Jeff

[Hypr5]

These little things have voltage... maybe it's time for a heater core bypass. :(
bah.

thanks!

[Hypr5]

After reading, it is my understanding that the coolant flow is pretty weak and is boosted by the aux. (electric) coolant pump. How true is this?

If that's the case, do you think I'd have any luck by simply unhooking the electric pump?

Thanks again.

[JonE]

I doubt it will help much as the aux pump is useful for those of us in cold climates, where I get some heat fairly soon after venturing down the road. I did have to replace the aux pump and noticed that I was still getting heat. That pump is connected directly to the water valve anyway, so, when you remove it to replace, it will be right there connected to the pump. A couple of needle nose vise grips on the hoses going into the heater core will help keep the coolant loss down significantly when replacing it...

[shogun]

I had a dead aux pump last year (usually cracks at the bottom where the motor is housed and then the motor goes south). I only noticed that in winter when engine RPM were low such in traffic jam or in front of red signals. Temp went down immy inside cabin as the water pump was at low RPM = circulating less coolant, which is usually supported by the aux pump.
Well, the valves and the pump lasted 17 years without problem. Changed them all together against new ones, so no prob anymore for the next 17 years to come. ;)

[Hypr5]

I had a dead aux pump last year (usually cracks at the bottom where the motor is housed and then the motor goes south). I only noticed that in winter when engine RPM were low such in traffic jam or in front of red signals. Temp went down immy inside cabin as the water pump was at low RPM = circulating less coolant, which is usually supported by the aux pump.
Well, the valves and the pump lasted 17 years without problem. Changed them all together against new ones, so no prob anymore for the next 17 years to come. ;)
Thanks guys!

checked voltage - played with the valves power open close open close to see if I could have any such luck and.. nope. Power, but apparently valves weren't closing all the way.

Bypassed the heater core and BAM, I have cold air. I love it.

Perhaps I should just go buy those manual water valves from Home Depot, Orchard,etc - made for garden hoses and put those on the lines - then when the cold climate comes, I can just open them! haha... that would be funny - but VERY cost effective!

[uscharalph]

It seems a few of us are bypassing the heater core these days.