Evaporator Temp Probe Questions

[pcarenthuz]

I'm rebuilding/restoring the HVAC unit under the dash and figured I would replace the evaporator temperature probe while I'm at it.

Does anyone know of a probe that will work other than the specific part BMW number 64511386920? The reason I ask is they seem to be $170 or so and one for other models like an E39 can be had for $40. Has anyone ever looked into this?

Finally, is there a way to test the functionality of the probe on a bench --I assume its resistance varies by temperature?

Many thanks,

Pat Arnold

[ZeKahr]

I'm rebuilding/restoring the HVAC unit under the dash and figured I would replace the evaporator temperature probe while I'm at it.

Does anyone know of a probe that will work other than the specific part BMW number 64511386920? The reason I ask is they seem to be $170 or so and one for other models like an E39 can be had for $40. Has anyone ever looked into this?

Finally, is there a way to test the functionality of the probe on a bench --I assume its resistance varies by temperature?

Many thanks,

Pat Arnold

I doubt the E39 evaporator probe will fit unless you’re willing to hack up the wiring; connectors are different and then there’s no telling if the probes differ in length. The evaporator temperature probe is a simple on/off switch that opens at around 32F to prevent evaporator icing.

[pcarenthuz]

Okay, good to know it's merely an on/off switch. Easy enough to tell if it's working with a can of super cold or the like. Appreciate the reply.

[S.J.1981]

That sensor is basically for the de-icer, it sends a signal to the compressor when it detects a temperature drop to near freezing, to prevent the evaporator from icing up.

The same sensor on the E30 is found on the E28, E24, E36 Z3 (coupe and roadster) as well as the Z8.

[pcarenthuz]

Okay, good to know, thank you. It's interesting the same sensor is found in the Z8 as well.

I tested my current probe and was not able to confirm an open condition at or below 32* F but it did change to a high resistance.

[S.J.1981]

Okay, good to know, thank you. It's interesting the same sensor is found in the Z8 as well.

I tested my current probe and was not able to confirm an open condition at or below 32* F but it did change to a high resistance.

Here is the test for the sensor on the evaporator temperature regulator:



I guess pin 1 and a ground is the resistance input the sensor sends to the regulator, i am uncertain.

This is what Realoem shows:

[agent]

The FAQ/DIY section is for staff-approved instructional posts only. Please do not ask questions there. If you don't know where to ask your question, post it in General Technical and we'll move it to the appropriate subforum if necessary. Thanks in advance.