Ambient sensor
 

What is the purpose of the ambient sensor for A/C on a 72 Lemans? Also, is there a way to check if it's working? On top of that, My wires going to it are just that, wires. No plug. Where would I source the two terminal receptor plug to affix my hanging wires?

The ambient sensor prevents the A/C compressor from engaging at low outside (ambient) temperatures. I think its set around 40*. Contact terminals should be closed (0 ohms) when measured with an ohmmeter above 40* plus or minus a few degrees. Put it in the refrigerator for awhile to test contact opening. I may have the plug you need in one of my spare harnesses. Does it look like this?

Thanks for that info. I will test it. Mine actually is on top of the cowl and two terminals come up about 1/8" and turn 90 degrees forward for the plug.

Went out to the garage. 28 degrees and checked the ohms reading and got nothing. Does that mean the ambient sensor is bad? I fired up the garage gas heater now for 70 degrees to work in this afternoon. I love my old house furnace out there!!

So far so good. It should be open or "nothing" at that temperature. Get it above 50* and check again. Should read zero on the meter.

Ok, I thought I was suppose to see zero when checking cold (below 40), and see a number when warmer. So, no reading was good and when warm I should see zero?

I think the plastic plug end to this sensor is a fairly common style/size used also on other electric connections. If you can't find one locally let me know & I can mail you one off of a spare harness I have laying around here.

Yes..
I reviewed the circuit in my diagnosis manual and it mentions the switch opens at freezing (32*) Given the age of the switch and other factors I would say you should see 0 ohms between 32 and 45*. If it's still open past that point I'd buy a new one.

Yes, maybe I need a new one since it shows no difference when tested in extreme temps one way or the other.

Thanks for the offer Steve. I'll see if I can source a plug.

I just checked mine and it`s good. I put it in the freezer for a while. Infinity. Let it thaw for a while, .1 ohms. Thought an almost 50 yr old sensor would be bad. Works fine.



I have never had a/c in this car since 1985. It`s going back now. Make sure you sand down the terminals a bit. Mine were dirty and causing a false reading on the DVOM.