Dammit, heater valve didn't fix my heater...

[Dan in NZ]

For the last year, my heater would be working fine for any amount of time, but would then go stone cold. The heat always came back if I turned the drivers side temp to full hot, but every now and then it just doesn't do warm. I assumed this was the infamous heater valve problem, but I installed a new one a few days ago, and still the same. Maintains temp for x amount of time, then goes cold, always comes hot again at full hot.

I'm now trying to think what else could be wrong... Perhaps 1 of the 5 temp sensors is faulty? Or a loose connection in the IHKA? Help!

[winfred]

possible dead aux pump, see if it works

[Unregistered]

From Dan,
Aux pump is ok, I replaced that too... I noticed today that I hear air flaps moving (the clunk coming from the heater) just before the heater goes cold. The IHKA is switching to stone-cold air for some reason, just got to find out why...

[JonE]

Dan,
Is your coolant system properly bled? Also, does the system maintain the proper cabin temperature when you set the dial? Perhaps it reaches the correct temp. then shuts down because it doesn't need to "heat" it up anymore? It seems this would be the action of the valve, but you mentioned flaps moving. I'm not sure how that part of the system works, sorry.

[Phil M]

yeah, my AC does that ****. blows fine in the 1/2/3 setting and then just stops blowing. Then comes back on once it starts getting hot again. I guess its a 'feature'. It takes too long for it to come on, hell by that time im already feeling the sweat starting to come. I wish our climate controls came with an Auto button so I could turn that **** off. I know, I know running it at 4 takes care of this. Blah


Dan,
Is your coolant system properly bled? Also, does the system maintain the proper cabin temperature when you set the dial? Perhaps it reaches the correct temp. then shuts down because it doesn't need to "heat" it up anymore? It seems this would be the action of the valve, but you mentioned flaps moving. I'm not sure how that part of the system works, sorry.

[Jeff N.]

Was it a new HCV? There's a simple test you can use to verify the basic signalling to the HCV. If you put in a new HCV and it's still having problems, I can try to summarize the test for you.

[Mr Project]

"Always comes hot again at full hot"

I think this is your key to trouble-shooting. There's some kind of heater 'WOT' switch that gets activated when you go full hot on the dial, and it doesn't mix anymore. Sounds like the issue maybe is in the mix control, and not the actual coolant plumbing.

[Dan in NZ]

Drove for an hour, heat was perfectly maintained, then it went cold... Left it to do it's thing to see if it would come right, then I started shivering and could see my breath in the car... Back to full hot with a window cracked open.

I'm going away for a few days, but when I get back I'll try to figure out why the mixing signal isn't getting to the valve. Might even have to try swapping IHKA or something to see if it hs any effect. Air flow is always constant.

The problem with these intermittant faults, is trying to catch the car when it's acting up!

[Jeff N.]

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