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Heating, Ventilation and Air Conditioning

E36 test functions.

About a week ago someone on the digest "hacked" their way into the test functions for their 328 heating system. Here are how this feature works:

The IHKA of the 1996 E36 has a feature that allows different sensor values to be displayed on the control panel. The display mode is called up by pressing the "AUTO" and "REAR DEFOGGER" buttons simultaneously. 12 displays are available and you can toggle through them by pressing the fan rocker switch.

Test number Function
1. Interior Temp Sensor
2. Exterior Temp sensor
3. Left Heater Core Sensor
4. Right Heater Core Sensor
5. Evaporator Temp Sensor
6. Engine Speed Input
7. Road Speed Input
8. "Y" Factor Value
9. Fresh Air Flap Position in % (99.5% Max.)
10. AUC Sensor Voltage (if equipped)
11. Battery Voltage
12. Software Version
The sensor display functions are exited by pressing "RECIRC" and "AUTO" buttons simultaneously and also by turning the ignition off. The decimal point is not shown therefore 66.5% would show as 665 All temp displays are in degrees centigrade. Negative values are indicated with minus sign

E30 Blower problems.

The fan in my '90 325iC stopped operating in the 1,2 and 3 position but will operate in the 4 (highest) setting. I think I once read something about replacing a "fan control module" or something similar in name. If anyone has information or a previous post which describes how to diagnose and resolve this problem I would greatly appreciate it if you would e-mail it to me at or post it publicly. As my Bently has been ordered, I intend to DIY this repair.

Thanks in advance,

This sounds like something wrong with the Blower resistors or safety switch. When the control is in pos 1-3, current goes through 1-3 resistors and a overheat safety switch before going to the blower. In pos. 4 current goes directly to the blower. Since it doesn't work in pos. 1-3 I would suspect the safety switch or the resistors. On the '88 the safety switch is inside the blower housing accessible from the engine compartment, behind the cowl cover. The resistor is the most common failure, however.

> ...I found out
> that neither the fan or the AC work at settings 1 to 3, but do work at
> setting 4 (max fan speed). Nothing at all happens at 1 to 3.

Common problem. BMW uses series resistors to reduce voltage to the fan and produce the slower speeds. You just lost the resistor board. The AC doesn't work because it senses the airflow before it turns on.

The resistors are easy to fix, but somewhat hard to get to. Look on the top of the firewall from the engine compartement. There is a section about 18" long by 6" high right at the top which is removable with a couple of screws. You will probably have to take off a few wires and tubes from the firewall as well. After you remove that section you will see the top of the HVAC unit sticking out of the passenger compartement. Remove the plastic cover (held on by a couple of straps if I remember right) to see the fan. The fan motor is a horizontal cylinder with a squirl (sp?) cage fan at either end. The resistor board is slid into the HVAC case below the fan. It is a small board, about 1-2" square, with 3 bare wire resistors on it. You pull it out toward you, nothing to detach first, it has plugs on the far side. Either you lost one of the resistors, or the contacts are dirty. Check it with an ohm meter. Installation is the reverse of removal ;-)

good luck,