Hot air for Defrost always?

[WHIPP525i]

I am new to the E34 and working on getting an owners manual. So please forgive the questioning if its not so intelligent!

My windsheild defrost always blows hot air (when the lever is moved in the defrost position), even when the AC is on.

FYI - I just got the AC recharged.

Is that the way its designed?

[4500 RPM]

No, I think the doors are stuck open. Mine does it too, along with the floor.

Solution? Use the A/C on dash vents only :rofl I can't remember what my mechanic said the fix was...something about a stepper motor maybe. :shifty

[kalevera]

Defrost uses heat to remove frost, presumably from the exterior of the glass. Defog uses AC to remove moisture from the inside of the glass (and the rest of the cabin). There's no pure "defog" function (or defrost, for the matter) on E34s with regular climate control, just open the upper vents and turn on the AC, same effect.

I have an owners manual set available, if you're still looking...PM me...

[paanta]

mine does this too. If anyone has an easy solution...

[quick93]

Same here, heat from the defrost and floor no matter what. I had an issue where the center dash vents would just start blowing hot for no reason then go back to cool but I fixed that by replacing the control next to the stereo.

[WHIPP525i]

PM sent....

[himarx525iwagon]

Normal operation is for a/c to blow from front vents (and maybe the dash vent, I'd have to check) only and hot air through the otheres, according to the owners manual. Keep the center slider all the way to the right, the floor and defrost sliders closed (to the left) and that's the way they built it..go figure.

[jehu]

I read you're supposed to have the bottom slider part way open for the temperature senor to function but then as it blows Hot if you are in Hot Summer Weather your feet cook... Could the Water valves be failing to shut fully? I really want to understand this because I seem to recall at some time I DID NOT get Heat from the De mister or Foot well when I had the settings for FULL COLD and would open them.... They blew the same as what came from the Center dash vents with AC on... COLD... which is the way it should be until you adjust the heat to have demisting... with the manual controls, that is the three dials,three sliders and three buttons( Rear defrost,Recirc and AC) You have the Temp Wheel between the two Dash vents ( Driver/Passenger) and that wheel if I am correct operates a switch which opens or closes the Water valves. Th water valves either allow or prevent heated Coolant from entering the Heater Core. If the Wheel is turned all the way into the Blue(down) it should fully shut the water valves allowing NO Heated Coolant into the Heater Core so if that is the case how then could you still be getting hot air at the Foot Well and Windshield demister???? This is not how mine is working currently.. I am now getting what most describe... Hot Air at Feet and Windshield with AC on and I think this is faulty operation. Am I incorrect?

[tonyroc14]

I read you're supposed to have the bottom slider part way open for the temperature senor to function but then as it blows Hot if you are in Hot Summer Weather your feet cook... Could the Water valves be failing to shut fully? I really want to understand this because I seem to recall at some time I DID NOT get Heat from the De mister or Foot well when I had the settings for FULL COLD and would open them.... They blew the same as what came from the Center dash vents with AC on... COLD... which is the way it should be until you adjust the heat to have demisting... with the manual controls, that is the three dials,three sliders and three buttons( Rear defrost,Recirc and AC) You have the Temp Wheel between the two Dash vents ( Driver/Passenger) and that wheel if I am correct operates a switch which opens or closes the Water valves. Th water valves either allow or prevent heated Coolant from entering the Heater Core. If the Wheel is turned all the way into the Blue(down) it should fully shut the water valves allowing NO Heated Coolant into the Heater Core so if that is the case how then could you still be getting hot air at the Foot Well and Windshield demister???? This is not how mine is working currently.. I am now getting what most describe... Hot Air at Feet and Windshield with AC on and I think this is faulty operation. Am I incorrect?
ummm, you might be. I always wanted to know what that wheel thing was for. But I seem to get hot air when i want it, and cold air when i want it. So idk

[jehu]

ummm, you might be. I always wanted to know what that wheel thing was for. But I seem to get hot air when i want it, and cold air when i want it. So idk


So what do you use the wheel for or do you not touch it? You say you get heat when you want it... I do too but I also get it when I don't NEED it that being WHEN I HAVE THE DIALS and WHEEL set to FULL COLD then open the FOOT or WINDSHIELD SLIDER... I would think If I wan AC from the dash to cool me off there should be no heated coolant entering the Heater Core unless and Until I move the WHEEL UP to allow some in which THEN should allow Hot from the Foot which I would get when opening that slider or demister for the Windshield by opening the Top Slider if I need that.. Having some Heated Coolant entering the Heater Core at all times no matter where the WHEEL is set may be the way it is supposed to work but If it is I am getting too much mixing with the foot and windshield shut fully tight and when I crack the foot to get less hot mixing My feet get too hot... If I have a faulty Mixer Flap or Stepper Motor perhaps that is the answer, But at some time in the past I remember not having any heat mixing even if I had the foot well and windshield sliders fully open WHILE I had the AC on and the climate dials to Max Cold UNTIL I ADJUSTED THE CENTER VENT WHEEL.. I feel I have to use caps because in the three years I've tried to discuss this NOBODY has appeared to comprehend exactly what I was saying. Its as if everyone reads what they want to read and reply according to their own situation,lol...

[kalevera]

Hot Air at Feet and Windshield with AC on and I think this is faulty operation. Am I incorrect?

In theory the system is supposed to send some warm air to the footwell vents courtesy of the center vent switch, but never when the dials are set to full cold. At that point, all cold air vents should be blowing cold air, hot air vents should be idle. The switches do go bad. So do the control units...

[jehu]

In theory the system is supposed to send some warm air to the footwell vents courtesy of the center vent switch, but never when the dials are set to full cold. At that point, all cold air vents should be blowing cold air, hot air vents should be idle. The switches do go bad. So do the control units...


So I have another IHKR that three plug box goes down by the microfilter .Is that the culprit or the dash climate control unit with the sliders and dials? Euro Depot up the road has scads of them... or both... I tried the other IHKR unit but didn't see a change so I guess I'll try the controls..

The control dials do alter the temps coming from the center correctly according to the position set.. I always thought the center vent wheel opened or closed or pulsed the water valves and the dash controls operated the mixing flaps when there was a setting chosen other than max cold or max hot in which cases the valves were either fully open or fully closed. The mystery to me was simply weather the heater core was supposed to get a little heated coolant even when the wheel was all the way down to full cold . If not then there should never be hot air coming from the foot or windshield until you dial up the wheel opening the water valves allowing in some coolant becasue there's no other source for heat than heated coolant in the heater core ergo if i get warm or hot air from the windhsield or footwell when the wheel is dialed to full cold the water valves are allowing collant in to the heater core either because they are faulty or the switch which is supposed to direct them to close is failing to allow the full voltage to be apllied shutting them... I take it if that is happening then it is in the IHKR ...? That the vent wheel switch( in my case the belden cable operated) goes to the IHKR Module BEFORE the Water Valves and a fault in that unit prevents the valves from fully closing .. They definitely do open and close largely as for instance if I have the AC on and get cold from the dash with the wheel dialed down, if i then dial it up hot air rushes out so the valves are opening... must it not be they are simply not closing fully as the should?

[WHIPP525i]

Update: AC out of front and dash vents only.

[MoTouring]

You only get A/C out of the 5 vents in the front and the back 2 on console. This is one thing I hate about E34; technically advanced but can't direct A/C to floor or windshield? I forget who but someone posted the diagram from the bentley that shows what comes out where. Cliff notes version: heat only from floor & defrost vents, heat & air from aforementioned face vents. The reason for the wheel is that if you have heat on, you may want cool at face level (I use it this way during winter).