Ambient Air Temperature Sensor on HVAC Box

[NavyCPO]

So while Joe has been helping me with figuring out what in the heck is going on with my HVAC System, I keep finding these other issues.  Some Background, I bought my 70 Monte which was supposed to be an all original car.  And for the most part it is, except when it came to the A/C system.  The A/C didn't work and after some troubleshooting I decided to go ahead and buy a Compressor Kit for my car.  The kit came with the Compressor, the Reciever/Dryer and the Expansion Valve.  As I went to try and find the Expansion Valve (I had no idea where it was and started to tear into the HVAC box, when luckily Joe stopped me cold and showed me how the system was supposed to be and the Expansion Valve is located outside of the HVAC BOX.  Whew!!!)  Well come to find out there was no where to tie in the expansion valve because somewhere along the line someone replaced the evaporator and did not put in the correct Evaporator and also added a 2nd Receiver/Dryer and elminated the POA Valve and there was nowhere to install the expansion valve. (See Image 1) I'm going back to the original setup EXCEPT for the POA Valve by ordering the POA Valve Update kit (See Image 4) from https://www.oldairproducts.com/.  I'm also opting to go ahead and replace the condensor since I'm going from R12 to R134A just to play it safe.  The Evaporator can be flushed and I'll have them do a Vacuum leakdown test prior to ever servicing the system up and running the new compressor.  The POA Update kit will delete the POA valve which have a history of sticky plunger (what I've read) and provide a place to tie in the Expansion Valve to help regulate the refrigerant, as well as adds a Pressure Switch for cycling the compressor as in newer vehicles.

So after all this, and Thanks SO MUCH to JoeT for his bending over backwards to help me figure this stuff out, I have been digging around the engine bay and I found this 2 pin sensor on the HVAC box with no connector on it.  (See Image 2)  So I'm scratching my head thinking now what?  Where is the connector for this thing?  Do I need it?  After researching the service manual and again with Joes Help, I found that that is actually the Ambient Air Temperature Sensor which is what was used to cycle the Compressor on and off with the original system and POA Valve in place, instead of the pressure switch used on new systems.  When the Air Temperature in the Evaporator gets below 37' F it opens and shuts down the compressor, when it is above 37' F it turns the compressor on for proper cooling.  It prevents the Evaporator from freezing and helps maintaing system efficiency.

So after reading this, I said Ok so where is the connector for that?????  Sounds like I need it.  Then it dawned on me that the improper upgrade made to my system had a pressure switch on the added on receiver/dryer and THAT is where my 2 wires are for that Ambient Air Temp Sensor. (See Image 3) Eureka!!!!

And then I realized that since I'll be adding the POA Valve Update Kit, it comes with a pressure switch and those 2 wires will be attaching to that.  (the kit comes with the proper connector for the switch instead of 2 spade terminals which is what I have now.) So that lonely old Ambient Air Temperature Sensor will continue to sit there unused and all alone. Sigh....BUT!!!!  If you still have your POA in place, YOU NEED IT!

 

And lastly, the 3 Pin connector on the right side of the HVAC Box (See Image 2) is the Blower Motor Resistor.

 

Hope this information may be useful to someone who may come across a similar jury rigged system as mine.

[jft69z]

It's been a pleasure Dale, trying to figure out what the prior owners have left you 🙂.

I don't think we're done yet in regards to that 'Ambient Switch' though. My system has that wired in series with the new cycling switch that's going to be on the POA eliminator manifold.

 I got a new A/C harness from American Auto Wire at the time, as a direct factory replacement. I left that ambient switch in place to prevent evaporator freeze-up and wired in that new pigtail for the cycling switch into the circuit.

I'll give you a call later.

 

 

Here's a pic of the harness from AAW. The circled connector goes to the Ambient switch with the Green & Tan wires.

When I rewired it though, I replaced the green wire in that connector to a brown jumper wire that goes to the new cycling switch plug. (I changed the wire colors in the new cycling switch plug to better reflect the factory colors. That's the plug on the right side of the picture). I then tied the green wire from the original harness to the cycling switch as shown to complete the circuit.

 

 

[willie]

Dale see how good Joe is, Think about how good he could really be if he got out of the hot tub now and then!!!  lol

[jft69z]

1 hour ago, willie said:

Dale see how good Joe is, Think about how good he could really be if he got out of the hot tub now and then!!!  lol

Hey now, let's not get crazy...

[NavyCPO]

8 hours ago, willie said:

Dale see how good Joe is, Think about how good he could really be if he got out of the hot tub now and then!!!  lol

Last time I talked to him he was on the couch!  LOL

[Dtret]

1 hour ago, NavyCPO said:

Last time I talked to him he was on the couch!  LOL

With a bag of chips and a dog on his lap. 

[jft69z]

9 minutes ago, Dtret said:

With a bag of chips and a dog on his lap. 

About 20 minutes ago..