Heater Valve / AC questions

[David.X5]

I'm getting hot air coming out of the center-right vents.

I have checked the following:

1) AC clutch is cycling on and off as it should. Static and Dynamic pressures are within range.
2) Aux fan is running as it should
3) Removed heater valves and they both operate with 12V applied. From this experiment, I learned they are normally open and stop flow with 12V applied.
4) Both heater valve solenoids measure 12-12.5 ohms, so they are drawing about 1A.
5) When I call for AC, I get 12V on one heater valve but not the other - think this is my source of heat!

So - think this is my problem - why is one side calling for heat???
Could be IHKA is fubar, but I would like to troubleshoot more.
Problem is one side, so am thinking about which sensors have a L & R...
Bad Interior air temp sensor?
Perhaps a bad heater core sensor?

Has anyone found a way to read these sensors directly?

[Joshdub]

I think you can read the sensor values in INPA. I am pretty sure I could when digging around in the climate control section.

[David.X5]

Alright - I've learned some more. Did pull the IKHA control panel to check the slotted openings - they seem fine (there is only one inside air temp sensor, still don't know what the two openings are for.

I have been using Autoenginuity software recently, so tried to connect to IKHA and was able to connect and read out the the temperature sensors

1) The L and R heater core temp sensors are reading 110F-150F and rise as the engine heats up. This seems right given that the heater valve is open.

2) The cabin temp reads 67.9 F and doesn't change - makes me think this is the minimum for the range. I don't recall seeing any DIY on changing the cabin temp sensor built into the IKHA panel - if someone has seen that, please point me in the right direction... This worries me, but I think that the next item should be first on my list, though.

3) The evaporator sensor reads 35.6 F and doesn't change - perhaps IKHA is calling for heat to prevent (wrongly) evaporator freeze up. I think I will try testing this one more.

[David.X5]

UPDATE - I sprayed some cleaner on the IHKA temperature sensor and it fell apart - only the dust was holding it together. So will work on replacing that, too... Still looking for a DIY on replacing that one piece inside the IHKA module

[David.X5]

Looks like I need a new Ihka module. Can't figure what else it could be.

Removed the evaporator sensor and it tests fine on the bench. Resistance changes as it should. About 2.5kohm at room temp and 7.5kohm in ice water. Hooked it back up and evap temp in Ihka never changes. Doesn't matter if car is running even.

Opened up Ihka and soldered in a fixed 470 ohm resistor to fool it into thinking it has a working temp sensor. No dice. Temperature remains unchanged in Ihka. Was also hopping this would let me confirm the temp range for the varistor. Nope...

[David.X5]

Update - Spent a lot of time reading sensor values using Autoenginuity software.

First, replaced the module which brough back the cabin temperature sensor and evaporator temperature sensor.

FWIW, there is only one cabin temperature sensor (the IHKA module has an open intake and one fake grill, no air can flow through it).

There are two heater cores and two heater core temperature sensors. I could see the signals calling for the heater valve to be closed, but one heater core was warming up - and one was staying at cabin temperature - that side of the heater valve was passing heat when it shouldn't - so new heater valve is on its way. ECS had a new OEM valve for $100. The ebay rebuild kits are $55, so just bought the new OEM version.

From what I learned this week, I would use software to diagnose any center-hot AC problem and not jump to conclusions - mine was a combination of electronic failure in IHKA and a leaky heater valve.

[David.X5]

The aftermarket heater valve (Hamburg Technic) arrived dead. Waiting for a BMW heater valve now

[Alika808]

Originally Posted by David.X5

I'm getting hot air coming out of the center-right vents.


5) When I call for AC, I get 12V on one heater valve but not the other - think this is my source of heat!

So - think this is my problem - why is one side calling for heat???
Could be IHKA is fubar, but I would like to troubleshoot more.
Problem is one side, so am thinking about which sensors have a L & R...
Bad Interior air temp sensor?
Perhaps a bad heater core sensor?

Has anyone found a way to read these sensors directly?

For troubleshooting purposes, try to disconnect the connectors of the heater valves to override the valves not to sending heat into the A/C system.

[David.X5]

Thanks. The valves are "normally open" so they would be open if you disconnect the wire and I would get full heat! To force them closed requires 12v to each valve.

I have noticed IHKA doesn't like it when I disconnect the heater valve wire while it is operating. Not sure if that is my imagination, or the output needs a drain for the current (think CB radios - you would destroy the output stage if you pushed transmit with no antenna connected...).

[Alika808]

OK, how about disconnect and plug the coolant hoses going to the heater core to eliminate the heated coolant enter into the system.