1998 E36 328i conv. AC Compressor does not cycle

[jerrycastillo]

Hello,

My AC had stopped blowing cold. The compressor clutch was not rotating. Checked the system and found out the compressor relay (yellow 61 36 1 389 105) was dead. Replaced it. Now the AC blows cold air again.
The compressor clutch engages when the snowflake button is pressed (the car has a IHKA system) and stays ON until the snowflake button is pressed again.

My doubts:
Shouldn't the compressor cycle ON and OFF directed by the DME?
Do these models have a variable displacement compressor that does not need to cycle?
Do these models work the air flow to let some hot air into the evaporator instead of cycling?

Thanks for any leads!!!

Jerry

[boarder2k7]

The compressor should be on full time at idle depending on temperature, maybe a very slow cycle. The system cycles based on high side pressure only, the DME doesn't cycle the A/C.

If your system is a bit low on refrigerant it won't cycle as well.

All I'd do is check temps. Today in 90 degree weather I was pushing 40 out the vents. You should see at least a 30 degree differential to the inside (center vent, full cold, fan on medium). Minimum achievable temp is 38 degrees on the vent as set by the thermostatic expansion valve. If your temps are okay, don't sweat it! I wouldn't even open the caps to check pressures if you hold good temps.

[JDStrickland]

There is a Failsafe switch that looks at the System pressure.

Your report sounds like you have low pressure, which means you need to have the system serviced.

[B320i]

I've found the system doesn't really cycle at idle in very hot weather - in fact, it seems to very briefly cycles off before immediately cutting straight back on in such circumstances (like the tick-tock of indicators in terms of speed).

Once you're at speed, it should do something.
Again, in very hot conditions (40ºC/104ºF or above) you will often find nothing happens on fresh-air mode. Both climate control (i.e. driver/passenger sets an actual temperature on either dial or display) should recirculate when the cabin becomes sufficiently hot.

Trying manually selecting recirculate, and see if that gets the system to start cycling. Again, the system may not cycle much, if at all, in very hot conditions with fresh air, but will do so to some extent with re-circulation active.

Might be prudent to double-check your fan clutch is working properly, and the electric fan is also working correctly. As I understand, it should actually go to high-speed if the pressure gets too high...

Little Story:
On a long drive in this past Aussie Summer, I was in conditions upwards of even 45ºC (113ºF). I had to set the control wheel to blue to override climate control and recirculate as the air just wasn't cool enough. Even setup like this, with the Fan on "3," the A/C did not cycle once in the couple of hours at (and probably several degrees above!) this extreme temperature. Suffice to say, it was still pretty cool.

[jerrycastillo]

Thank you 2k7, Strickland and B320i for your answers!

[boarder2k7]

Thank you 2k7, Strickland and B320i for your answers!

Happy to help!

B320i brings up a good point as well, the system definitely won't cycle when it's really hot. The expansion valve is thermostatically controlled and is trying to get the air temperature in the evaporator compartment down to 38 F, at which point it will close, allowing the high side pressure to build. If the air never cools, the valve will stay open and it will run.

I found myself thankful again today for BMW's good A/C though... 89 and 60% humidity and still nice and cool inside!

[masCh]

Hi, I know this is an old thread but I used to search function to find something related to my problem.

My outside temperature is 35C (95F+) and my air-conditioning, as far as I can remember since I got it some 25 years ago has always had this problem where the AC goes so cold that it freezes until the vents start fogging and there's little air flow from the vents and cabin temperature starts to rise. If I stop the car and go outside, there is no water dripping from the bottom until like 5 mins heated by the hot sun, then suddenly cold water starts draining in large quantities from under the car.

How I have managed this is I turn on the AC (snow button) then switch it off after 10 min then switch it on again manually.

From what i read is that the climate control module or IKHR should be doing that automatically? Is that right? What controls the cycling of the compressor so that I could test the signals from the connectors?

Don't know if it matters but I have a digital climate control and I don't know where the IKHR is yet, I assume the IKHR is what cycles the compressor?

Also another related thing, my heater coil is leaking coolant so that has been sealed off, there is no heater in the vehicle which I think means I can't control the climate in the car, except by cycling the compressor.

I'd like my vents not to freeze up and block cold air though.

[shogun]

here some info IHKA, IHKR , study that, I assume your problem could be a temperature sensor, evaporator temperature sensor (?)https://ia801005.us.archive.org/11/i...IHKA%20E36.pdf
E46 IHKR might be similar https://ia801005.us.archive.org/11/i...IHKR%20E46.pdf
IHKS https://ia801005.us.archive.org/11/i.../04%20IHKS.pdf
diagnostic https://www.forumbmw.net/img/members...-IHK-Codes.pdf
IHKR: The IHKR system is a “semi-automatic” climate control system. Interior air temperature is controlled automatically, but air distribution and blower speed are controlled from the control panel by the driver. IHKR was used on the some early vehicles such as the E34 and E36 (up to 95). The most recent use of the IHKR system was on the E39 525, E53 X5 3.0, E46 325 and the E85 Z4 as standard equipment (IHKA was available as an option). IHKR is also a single zone system, with only one temperature control for the entire passenger cabin.