Cabin Constantly Hot, Need Help

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Neveragain55
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Cabin Constantly Hot, Need Help

Post by Neveragain55 »

Hi Gang,

So, for whatever reason each time I drive the car there is a ton of hot air coming out of the floor vents, even though the temperature controller is dialed all the way to cold.

She never did this before and I recently purchased a brand new heather control valve (authentic BMW part) and it's still happening.

Needless to say I'm very confused over why hot air is coming out even though it's on cold.

Any & all ideas are welcome, thanks guys....
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Re: Cabin Constantly Hot, Need Help

Post by bpoliakoff »

Flaps on the heater box could be stuck open
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Neveragain55
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Re: Cabin Constantly Hot, Need Help

Post by Neveragain55 »

Thanks for the info, but are they located under the dash or where exactly.....

I guess what I'm asking is how do I access the flaps to un-stick them?

Thanks
1964 Ford Thunderbird
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Re: Cabin Constantly Hot, Need Help

Post by jps635 »

If your heater control is on full cold and your heater valve is working properly this should be regulating the water flow through your heater core.

The new "BMW" heater valve I purchased was not good. viewtopic.php?f=5&t=31277&p=223549&hili ... ve#p223549
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Neveragain55
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Re: Cabin Constantly Hot, Need Help

Post by Neveragain55 »

Thanks JPS635,

The heat control valve I bought was the super expensive BMW original unit, so I'm more than confident that its working properly.

I didn't but just the inner valve and repair the original unit, I purchased an entire new unit and installed it hoping that would eliminate all of the hot air coming into the cabin while I'm driving.

I just got the car back from paint a few months ago and it was there for close to three years (they took the car completely apart and painted it right, looks amazing but it took forever) All the glass came out, new seals & moldings around all the glass, new rubber around the doors, and the car was stripped down to nothing, all the rust was repaired with new metal welded in, no bondo anywhere.

The front seats came out to be reupholstered, maybe something got disturbed when they came out, I would have no idea.

I'm thinking that maybe something was disconnected or pulled apart by accident by one of the body guys and I'm just un-aware of it, or maybe because the car was sitting for so long something just got stuck either open or closed.

I do know that the cable that attaches to the center lever (on the climate control box) is off because the lever just slides back & forth with no resistance.

I had the A/C serviced by an A/C specialist and he told me to just pull the unit out and reconnect the cable to the lever to get the middle vents operating properly.

Maybe that's it, maybe the middle vents are in the open position while the other two are closed. But still, you would think that - that wouldn't matter as long as the temp knob is dialed all the way down to cold. Plus the hot air seems to be coming mostly from the floor.
1964 Ford Thunderbird
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1979 Suzuki GS750E
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1997 Mercedes SL500
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Re: Cabin Constantly Hot, Need Help

Post by hornhospital »

The intensity of the heat given off by the core is way more than the air conditioner can overcome. Reconnect that center lever.
Ken Kanne
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Neveragain55
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Re: Cabin Constantly Hot, Need Help

Post by Neveragain55 »

Got it........and thank you.......
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Re: Cabin Constantly Hot, Need Help

Post by 86_6series »

I would make sure the voltage changes to the harness @ the valve when you turn the heat control switch from heat to cool.
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Neveragain55
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Re: Cabin Constantly Hot, Need Help

Post by Neveragain55 »

That sounds like a two person job, one person to turn the knob while the other puts a meter to the tabs in the connecting lead that plugs to the top of the heater control valve.

Or clips the leads on (provided one has the clip style) and just position the meter to see it while turning the knob.

Am I looking for any particular voltage or just a variation to show that the knob within the car is receiving juice form a source, and then sending juice to the heater control valve???
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1979 Suzuki GS750E
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Re: Cabin Constantly Hot, Need Help

Post by 86_6series »

One person, unplug harness from valve.
With ign on engine not running.
Turn control knob to cool.
Measure voltage across end of harness plug.
Turn knob to heat.
Repeat measure, should have a voltage change.
If you do get a change in reading then I'd check that valve again.
If no change problem could be in the temp control unit-#7.

https://www.realoem.com/bmw/enUS/showpa ... Id=64_0094


Test the output of the control again cool to heat to see if it sends a signal to the valve harness.

Start with page 6411-0 of manual, page 108 of PDF. Page 113 of PDF has explanation of the circuit.

https://www.millerperformancecars.com/f ... Manual.pdf
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Re: Cabin Constantly Hot, Need Help

Post by Ralph in Socal »

Working on this same issue right now.

Three separate parts provide input to cabin heat. Heater Valve, Interior Temp Sensor, Rotary Temperature Dial.

The heater valve gets +12V to close it. No voltage and it’s open. Nothing in between.

Probing for voltage at the valve provides insight on what may be the problem. If the dial is on No-Heat yet there’s no voltage at the valve (valve is open) leads to the Interior Temp Sensor or Rotary Temp Selector Switch on the dash as faulty

Turning the Rotary Temp Selector Switch while probing for voltage at valve should change the voltage. No change in input is a good sign that one or the other is faulty.

But it’s not easy to determine which one is bad. For me having spare parts, I’m going to change the Interior Temp Sensor first as that is much easier to access than the dash switch. Good luck and let me know if you want a spare interior temp sensor

Ralph
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Re: Cabin Constantly Hot, Need Help

Post by gte619n »

Might be silly, but make sure the boot between the gear selector and the body is intact and well seated. I've had issues where the boot worked its way loose and engine/transmission air come rising into the cabin through the center console > floor vent area. It was very confusing!
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Neveragain55
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Re: Cabin Constantly Hot, Need Help

Post by Neveragain55 »

Thanks guys,

All great replies, and I'll check all of these things out and come back with an update once I've had a chance to look at and test these issues.

Right now the car is back at my painters shop for the final detail & polish before she gets tucked away in the garage for the winter.

Plus there were a couple of "trim issues" I needed him to address to really call the car complete. (yeah I'm SUPER anal like that)

Once I get her back which should be about a week or two I'll get right on it.

Thanks Again.....
1964 Ford Thunderbird
1970 Lincoln Mark III
1977 Datsun 280Z
1979 Suzuki GS750E
1989 BMW 635 CSI L6
1997 Mercedes SL500
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Re: Cabin Constantly Hot, Need Help

Post by Tommys 89 635 »

Put a flashlight in the engine compartment (driver's side) and look under the foot well of the drivers side, maybe a grommet has popped out. That will also let engine heat in.
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Re: Cabin Constantly Hot, Need Help

Post by Lbs6 »

It seems simple, but don't forget to check your fuses. I had a power seat switch stick with out my knowledge. Next time I drove the car it tried to roast me. Circuit runs the AC, power seats, heater valve. Don't remember what else.

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Re: Cabin Constantly Hot, Need Help

Post by jbmike »

1983 633 CSI - Same issue constant heat in the cabin. Above posts were very helpful however I sense I have a couple of problems (read:$$$). I'm getting a solid 12v at the valve when the temp dial is on max heat or max cool which indicates a problem with the Rotary Temp Selector unit. The fact that I have 12 volts going to the Heater Valve yet both the input and output hoses to the heater radiator are hot, along with heat in the cabin, means the valve is messed up and stuck open. Plan is to buy a new heater valve - as long as there's 12 volts going to it, it should remain shut and eliminate my Summer sauna effect. Its a Summer car and I'm not planning on driving it in the Winter - I also line in New York where they enjoy covering the roads with salt once the word "snow" in mentioned. Worst case situation is if I urgently need to drive it in the winter I'd just unplug the wires going to the Heater Valve (kill the perpetual 12 volts) which should open it up and allow hot coolant to again flow through the heater core.

Am I missing anything here or does this kinda make sense ---- Yes, the end game is to resolve the Rotary Temp Selector issue but that's far more work than merely replacing the heater valve....

Mike
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Re: Cabin Constantly Hot, Need Help

Post by Ralph in Socal »

Your intentions seem proper to end the heat inside the cabin. The valve solenoid activates when +12V is provided and removed. Plug and unplug to determine if the solenoid is good. Typically the rubber insert parts fail and need replacement. Much cheaper than an entire valve. I actually have a couple of the membrane internals from MBZ cars as they use a very similar system.

Ralph
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Re: Cabin Constantly Hot, Need Help

Post by jbmike »

Thanks for the feedback Ralph. I'm not hearing/feeling any "solenoid click" when power is applied/removed so I'm thinking its toast.... Just going to order a new valve and call it a day - pricey but it could be a lot worse.
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Re: Cabin Constantly Hot, Need Help

Post by jbmike »

Finally got back to this. Did a bit more fiddling around and ran a positive and negative directly from the battery to the heater valve and lo and behold I heard that magical "click" as the solenoid engaged. Went back to the wire loom plug that goes into the heater valve and it still had a positive on one socket -- checked the second socket and it was NOT grounded .... Does anyone know if the heater valve solenoid is actually triggered by a positive 12v or could it in-fact be triggered by a ground signal from some relay???

Wish I had a wiring diagram handy to track this down...

...Mike
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Re: Cabin Constantly Hot, Need Help

Post by 86_6series »

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