I have a question on what controls cycling of AC compressor on OE AC car? What is the purpose of the temp probe/switch that goes in the evaporator?
The temp probe, signal the temp and when it reaches the temp 42 to 38 cold degrees it tell the expansion valve switch to cot off the power of the compressor, and other is when the system is low in freon the high pressure switch starts to cut off on and off the power to the compressor and the correct pressure low 35 high 150 on the gauges system running normal that’s my understanding
If temp probe doesn't cycle compressor, the evaporator will freeze. Modern systems use a pressure switch on low side that cycles compressor to prevent freezing.
So far, I don't think I have had evaporator freeze. I installed a NOS probe/sw Maverick specific from Ebay; not sure if the switch is/was defective. I just ordered a new switch for earlier Stangs I plan to install and see if that is the problem. So the probe is the equivalent of "modern system low side pressure switch" on our cars?
I don't remember removing the probe on my stock system but I do have a trinary switch on my dryer w/508 Sanden sompressor. I may check on it to see if by chance they may be working against each other in some way.
I removed all of the OE - AC components cept the evaporator; replaced w/ R134a Classic Air system upgrades including Sanden compressor. I went through the heat/ac box , painted all rusted parts, replaced vac. motors, etc. I am going to replace a NOS temp probe in evaporator w/ one I recently got from one of the Stang vendors and that should pretty much eliminate the issue of a faulty temp probe. My issue -- compressor not cycling -- gets to cold inside car. I don't know if the temp control slider on dash is working properly, it seems to work ok in the heater mode. I'd like to get this resolved soon, if possible --- hope to make road trip July.
"gets to cold inside car" never heard of such a thing...LOL if system isn't freezing up I see no problem. on one our July rode trips I have a pic of Effie wrapped up in a blanket with the A/C on low....
AFAIK, cycling the compressor has never been used as a method to control temp. On a factory system, temp should be regulated by blending recirculated cabin air along with cooled air, this is for max setting. For normal, outside air is blended with cooled air. Either of these settings reduce air flow across the evaporator, increasing possibility of freezing(thus the temp probe). Sounds like you have a blend door issue.
I believe you are correct on all counts. I notice putting the defrost on and temp switch in coldest position I get hot air from the windshield ducts. I don't know if someone have switch some vac hoses around or I did it when I had box out. I do recall putting hoses back where they were.
What setup do you have on the car now? Does your compressor cycle? How would you know if the switches are working against each other? I removed the probe to go through and clean/paint everything along w/ repairing a spot in bottom of the box. I replaced the original probe, but since, installed the NOS probe. I'm going to keep playing w/ the issue, cept, pulling the box out of the car. Going to run it like it is, for now --- too hot here, to be crawling around under the dash. I have a new master cylinder to install going too wait till better weather too mess w/ that -- at least, that won't commit a lot of time under dash.
compressor cycles... I have all newer stuff under the hood.box and everything under is stock style stuff. I will get with my A/C Guy and ask about the two being any problem.
