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Old 12-12-2019, 06:39 PM
tjs72lemans tjs72lemans is offline
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Default 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?

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Old 12-12-2019, 07:14 PM
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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?
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Old 12-13-2019, 08:52 PM
tjs72lemans tjs72lemans is offline
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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.

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Old 12-14-2019, 12:07 PM
tjs72lemans tjs72lemans is offline
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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!!

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Old 12-14-2019, 01:40 PM
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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.

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Old 12-14-2019, 08:53 PM
tjs72lemans tjs72lemans is offline
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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?

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Old 12-14-2019, 09:26 PM
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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.

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Old 12-14-2019, 10:36 PM
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Quote:
Originally Posted by tjs72lemans View Post
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?
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.

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Old 12-15-2019, 10:08 PM
tjs72lemans tjs72lemans is offline
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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.

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Old 12-22-2019, 11:43 AM
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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.

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