E36 HVAC always blows hot - controller or valve?

[marcva]

Hello list. It's been a while. My 1997 E36 is runbling along with 196k, and the problems have been pretty straightforward. I wanted to confirm my diagnosis before I start throwing parts at one of my current issues.

The car blows hot air all of the time. even when using the Air conditioning. this was an intermittent problem last summer, which made me wonder what was up with my HVAC here in SC. Now if I run the AC with multiple dash vents open an the Tstat set to 60, I'll get coolish air out of the dash vents and warm air out of the defroster vent.

Assuming this is the Heater Control Valve. Fiddly, but doable. Or could it be the AC control panel itself? I replaced my control panel based on some more catastrophic error a few years back.

Any issue with third party parts in this area vs Genuine BMW in case there's a huge price arbitrage?

Thanks,

Marc Plante
Mt. Pleasant, SC

[bmwdirtracer]

Hi Marc,

With HVAC set to a/c, temp set to 60, feel the hoses between the heater valve and the firewall, and between the firewall and the engine. Or, you can use an infrared temp gun (which are now dirt cheap at Amazon and elsewhere). If the valve is working correctly, they should be no more than barely warm.

The heater valve fails in the OPEN position, so if, say, the fuse for it is bad, the valve will stay open and send hot water to the cabin.

EDIT: Fuse 31.

[marcva]

Chris:

Thanks (again!) For the focused triage technique. I'll get to it today when I start the car. Since I work at home now, I don't a lot less than I used to.

Didn't realize you're in Fayetteville. That's almost a makeable drive it I have a larger project on the car. I've tentatively identified a local Indy since moving, but haven't been yet. The steering rack leak is slow enough, (but sure about needing with tie rods), and everything else has been manageable.

[dworthy]

I bet the temperature is a bit different now then up North eh?

You can also check for power at the heater valve, for if it's getting power and the valve isn't closing, then that's going to be the problem.

[marcva]

I don't expect to ever see snow here, though it does get below freezing. My golf clubs are out all winter, though.

Thermapen registered hot pipes at the firewall. Now to get to a couple YouTube videos to figure out how to get in there without removing the manifold. The first one I watched mysteriously skipped reconnecting the hoses to the new controller. It looks very tight from above. I'm hoping that it's better from below when I pick the car up.

[bmwdirtracer]

As Darin says, make sure there's actually power at the heater valve plug. It fails in the open position, so if there's no power, the hot water's going to the cabin.

Of course, I'll be glad to take good care of your car if and when you need to make the drive, but I'm showing over a three hour drive, each way. Now, that said, I've tended to cars sent all the way from Florida and DC, so Charleston's not so far.

[marcva]

I'll double check the power. The fuse was good, but I'll check power at the valve. My last mechanic had an e30m that came down from long island to DC a couple times a year. We shall see...

[marcva]

There is power at the connector to the valve, and the valve itself is looking green/corroded about the seams. Hoses are 26 years old as well. I a suppose they should be done. An I looking at pulling the manifold to get that third hose from the firewall that goes down to the block?

I've never pulled the intake manifold before... Another first. PCV's already been done recently.

[bmwdirtracer]

I'm no longer intimately familiar with what it takes to do those hoses, on an E36, sorry. I can tell you that I'd do my best to sneak it. IF you remove the intake, you need to replace every old rotten gasket you disturb, and every coolant hose underneath.. Can you just get to the valve itself? I mean....absolutely, you need to replace every original hose....

[marcva]

Yeah, in flipping through realoem and watching videos. That's kind of a S¢|tshow under there. I'm hoping I can pull the intake and maybe get a couple of the hoses to the firewall, realizing if something under the manifold goes it'll be a messy rebuild. I'll start small and be gentle. I can hear my old mechanic cursing already. Perils of a geriatric car.

[marcva]

Yeah, in flipping through realoem and watching videos. That's kind of a S¢|tshow under there. I'm hoping I can pull the intake and maybe get a couple of the hoses to the firewall, realizing if something under the manifold goes it'll be a messy rebuild. I'll start small and be gentle. I can hear my old mechanic cursing already. Perils of a geriatric car.

Ordered the new valve from my dealer up in VA (online discounts work pretty well). I'll be installing when it gets here. I'll stick with the current hoses for now, though I may end up doing the short firewall hoses if it seems convenient. The first time working on any new system is always a little scary for me, especially a 23 year old plastic and rubber system that can disable the car if something goes sideways.

I'll provide a post mortem.

Marc