A.W.O.L

I tried a search on AC problems, but couldn't find anything good.

For awhile now, my passenger side blows only hot, while the driver side can blow ice cold ac or hot. Has anyone seen this, or have a fix for it. My dials turn, but the passenger side ( right) is only stuck on full blast hotttt.

I might just take out the AC if there is not real fix for it.

Any help would be appreciated

- Scott

__________________
1991 M5 - cams n' slam y0

E34_nut

Hi Scott.

It sounds like the adjustment on the pax side has gone full scale. To check the circuit diagram, I need to know your VIN or build month/year.

Drop that info back to me and I'll take a look in the ETM and see if I can help debug this for you.

*******
One more thing, does your car have the
"Fully automatic climate control" - 3 rotary knobs each with 3 buttons under them or
"Standard Air Conditioning" - 3 buttons, then 3 sliders, then 3 rotary dials ?
*******

Regards,

Reg.

__________________
from THE Antipodes , the real Land of Aus.

"You're gunna die of something, it might as well be fun !"

'88 Ducati 851 Superbike Strada - the original tricolour
'83 Ducati Mike Hailwood Replica - "900" kick start

Imagine a luxo like an E38 "L" with the current 4.0L Diesel !

Gerg

I'm having the same problem. Could you help me too? The last seven of the vin are BL01001 and I have the rotary dials. The hot air comes from the small side window defrost vents.

Thanks,
Greg

__________________
'95 M5 six speed Sold
B10 Biturbo #362 Sold
'91 M5
"92 M5T #001
'93 M5T DV
"84 635CSI Euro

Alan Archer

Chaps,

the driverstemperature control knob has two stops, one at max cold
and one at max hot.
This is an overide to provide heat should the rheostat fail.

If you are saying that when you set the temperature to max cold..you
get cold from the drivers side then the controls are working properly...

Your problem is most probably the heater valve pack under the hood.
The valves clog & stick open.

The ultimate solution is to bite the bullet & replace the valve pack.


Best regards,

Alan.

__________________
///M5 the only substitute for capacity is even greater capacity...

A.W.O.L

My vin is WBSHD9319MBK05237. It has the fully automatic climate control

essentially, driver side works as it should. Passenger is always hot. Even the middle blower in the dash, towards the driver side, it is cold where the passenger side is hot - all within the same "vent"

E34_nut

What's in the system

• There are 2 separate heat exchangers in the airconditioning system of your car. One for the driver and one for the passenger.
• There are 4 temperature sensors in the system, they measure

1. outside air temp,
2. inside air temp,
3. temperature of the air being delivered by the drivers heat exchanger
4. temperature of the air being delivered by the passengers heat exchanger

• A bunch of servo motors to control where the air goes.
• A bunch of relays and controllers that manage the fan, the airconditioning compressor, the hot water control vavles and a whole lot of other "stuff".

How I think the system works.
Start off with something simple.
Both the driver and the passenger request the same temperature on their temperature dials. The climate control system adjusts the heating/cooling until the temperature sensor just behind the controls is measuring the requested temperature. Both heat exchangers deliver air at the same temperature.
Inside temp < requested temp -> heat until inside = requested
Inside temp > requested temp -> cool until inside = requested
Inside temp = requested temp & outside temp is not changing -> hold the heating/cooling as is
Inside temp = requested temp & outside temp is falling -> heat the air a little more
Inside temp = requested temp & outside temp is rising -> cool the air a little more

All easy so far [I hope], but what happens when the driver requests a different temperature to the passenger ? There's only one sensor measuring temperature inside the car, how can it work ?
This is where the heat exchanger sensors come into play.

When the passenger and the driver set different temperatures, the climate control system works the same as above but now it adjusts the heating/cooling until the temperature sensor just behind the controls is measuring a temperature half between the 2 temperatures requested AND it also sets the heating/cooling on the 2 heat exchangers so the heat exchangers are providing air temperatures that have the same difference as the difference between the temperature requested by the driver and temperature requested by the passenger.

First I found a mismatch between your description of which system is in your car and which system the ETK says is in your car. When I enter the VIN for your car in the ETK, it shows your car as having the semi-automatic system in the car, (3 rotary dials, 3 sliders & 3 buttons) rather then the fully automatic system (3 rotary dials, 9 buttons)

You can check at the on-line ETK
www.realoem.com/bmw/select.do
enter the last 7 characters of your VIN.
Browse parts
choose 64 [Heater and Air Conditioning]
choose 64 20 {Control]
Does the control unit in your car look like the units displayed ?
If so, you have one of 4 minor variations of the semi-automatic climate control system.

X85 is the 3 pin connector on the heater control valve assembly under the hood immediately in front of the driver [LHD]

Fully automatic wiring to heater control valves
water valve assembly [part Y4], left valve, X85-3 -> yellow/brown - X35-7 -> yellow/brown -> X610-21 IHKR Ctrl Unit [part A9000]
water valve assembly [part Y4], right valve, X85-2 -> yellow/violet - X35-8 -> yellow/brown -> X610-23 IHKR Ctrl Unit [part A9000]
water valve assembly [part Y4], common, X85-1 -> green/yellow -> X35-6 -> green/yellow -> X693-1 Climate Control Switch Unit [part S9000]

Semi-automatic wiring to heater control valves
water valve assembly [part Y4], left valve, X85-3 -> Yellow/brown, X35-7 -> yellow/violet -> X18154-14 IHKRII Ctrl Unit [part A87]
water valve assembly [part Y4], right valve, X85-2 -> Yellow/Violet, X35-8 -> yellow/violet -> X18154-16 IHKRII Ctrl Unit [part A87]
water valve assembly [part Y4], common, X85-1 -> yellow -> X35-6 -> red/yellow -> F20

Before we go delving into the wiring and the control system, it would be a good idea to check Alan Archers hypothesis above.

With the ignition on and the car running, set the passenger side temperature control to maximum cold, and the drivers side temperature control to maximum cold. Unless the outside air temp is really cold, in this mode, you would expect the heater to be turned off. To test this, pins 2 and 3 of connector X85, (on the heater control valves under the hood) should both be at 0V and pin 1 should be at +12V. If pin2 is at +12V, then the climate control system is actually turning the heater on for the passenger or the wire between the heater control valve and climate control system is open circuit (broken). If pin 2 is 0V, then the valve is jammed or electrically open circuit. Either way, I think it is likely to be the fault. This will prove Alan's diagnosis.

That's all I've got time for tonight (Monday). Will add to this Wednesday night my time.

Regards,

Reg.

Haven't had time to proof read this, so please excuse grammar, spelling etc.

davidoli

I also suspect that Alan is more than likely right .

On the positive side , heater valves have come down in price over the years and retail around the £100 mark approx now .

D

__________________
Better a day as a tiger than a lifetime as a sheep !

91 Sebring 3.6

E28 UK RHD M5

E34_nut

When I left off last time, I described how I think the climate control system works, given the inputs and sensors in the system.

Allan Archer's experience gave a great lead as to possible cause of the problem and hopefully my description of the wiring would help confirm Allan's diagnosis without having to pull the whole thing apart.

One thing I forgot to mention in my last post was why the voltage across the valves should be 12V when the car is NOT trying to heat the interior. If the fuse to the heating valves fails, or the control unit fails and there's no power to these valves, the valves will open and the interior of the car will be heated. I guess this is safety option so heating will be available if there is a failure in the system. Power applied to the heater valves closes the valves and stops heating.

Other possible causes.
Let's assume the heater valves are OK, what else could cause the problem.

Heat Exchanger Sensor Failure
Heater core temperature test values (from Bentley)
-20C - 84k4 -109k6 ohms
-10C - 48k6 - 62k1 ohms
0C - 28k9 - 36k4 ohms
20C - 3k8 - 11k1 ohms
60C - 2k2 - 2k8 ohms

These sensors will increase in resistance as the temperature falls.

What would happen if the passenger side heat exchanger sensor failed ?
If the heat exchanger sensor on the passengers side went "open circuit" or "high resistance", the control unit would think the air being delivered on the passengers side of the car was colder than is required to achieve the temperature requested by the passenger. To overcome this, the climate control unit might run more hot water through the passenger side heat exchanger to try and raise the temperature it is delivering to the passenger side of the car. If the sensor didn't change, then more and more heating would be delivered until there's no more heating available to deliver. It is possible the unit is smart enough not to do this, but none-the-less, it is possible.

Passenger Side Temperature Dial Failure.
It is also possible that the passenger side temperature dial has failed. If that dial has failed such that the dial looks like it's been set to request maximum heat, the control unit could request maximum heat from the passengers side heat exchanger.

In the case of the symptoms described by Scott, I don't think this is the problem for 2 reasons. Once the control unit measures the passenger side is 26 or 28C it should start to shut the heat off and secondly, if the drivers side control is set to maximum cool, it should prevent the passenger side delivering hot air.

Please, let me know how you go. If what you find is different to what to I've posted, I'll correct my post.

Regards,

Reg.

elroy

I figured I'd chime in on this one... I have the same problem -- it seems on the driver's side of my car, hot air blows out all the time... cold air will blow out too but there's hot air coming from somewhere... Seems to be down by my feet.

I've also noticed that when the heater is on, I hear/feel a knock from somewhere in the driver-side dash (or at least that's what it feels like)... Heater valve box is up in that area, mechanic said the same thing about them getting clogged and stuck... is the knocking due to that?

Anyway, just want some confirmation before I go buying parts...

E34_nut

Hi Elroy.

In my post "Climate Control, How it works [I think] and debugging" you may want to try going through the steps starting at "X85 is the 3 pin connector on the heater control valve assembly under the hood"

What these steps attempt to do, is see if the climate control system is really trying to heat the interior of the car.
Basically, the voltage measured across X85-6 & X85-7 and X85-6 & X85-8 should both be 12V if the climate control system is not trying to heat the car. So if the reading is a solid 12V and the car is being heated, there's fair chance the valves have failed or are intermittent. I'd try this on my car to check, but I can't run it at the moment.

If either of these measurements read 0V or are pulsing between 0V and 12V, the climate control system is trying to heat the car and the valves probably aren't faulty.

Let me know what readings you get before you rush off and buy bits because I'm providing this info based purely on the circuit diagram. I don't have a functional description of the system.

Regards,

Reg.