1965 Thunderbird AC question

[sshoureas]

Hello All, I'm new to the forum as I just picked up a time capsule 1965 Thunderbird. I bought it as having ice cold AC although after getting it home I find the compressor clutch not engaging. I jumpered the clutch and the compressor engaged so it seems it isn't getting 12V. The underhood wiring doesn't appear damaged anywhere, again its a low mileage not messed with car so hacked up wiring likely won't be the problem. I have the repair manual on the way but for now it seems it might point back the HVAC control in the console? Sound right? After jumpering the clutch the cold line did did cold and began condensating. The sight glass showed some bubbling so it seems it may be low. I couldn't pick up much in the way of cool air inside but again the refrigerant charge is probably too low.

Thanks in advance for any help!

[jopizz]

Welcome to the forum. My first thought is that you may have a bad thermostatic switch or a vacuum leak to the switch. Those small vacuum hoses have a tendency to get brittle and crack over time causing leaks. If you look at the manual when you receive it you will see the large number of vacuum hoses that control the AC system. The first thing I would do is to check all the vacuum connections under the hood including the vacuum canister. That can leak and cause the AC system not to function. Here's the diagram from the manual.

John

[sshoureas]

John - Great advice, thanks! The diagram shows I'll keep busy for a while making sure blend doors and so forth work as they should but the clutch not engaging would point to an electrical cause, correct? With a jumper to 12V it does engage so I'd assume its either a fuse, wiring or an issue with the HVAC controller in the console? Do these fail very often? The vacuum diagram should help me sort out whether the doors and other vacuum operated components are working correctly. I am encouraged though to find the cold line dripping with condensation when I jumper the clutch. That seems to point to the system generally being capable though with a bug or two to resolve.

Thanks again for your quick advice and the diagram.

[jopizz]

The thermostatic switch controls the clutch. If that's not working the clutch will never engage.

John

[sshoureas]

John - I'm getting ready to dig into this issue this week after clearly my plate of some immediate home projects. If the AC charge is low will that keep the thermostatic switch from allowing the clutch to engage such as more modern cars do to protect the compressor?

[jopizz]

If the AC charge is low will that keep the thermostatic switch from allowing the clutch to engage such as more modern cars do to protect the compressor?

No. The thermostatic switch only opens and shuts off the clutch when the evaporator gets to a certain temperature to prevent freeze up. If it's low in refrigerant the switch will remain closed and the clutch will still be engaged.

John

[Deanj]

That's good to know because I thought the clutch wouldn't engage if refrigerant was low. I thought the system needed oil to prevent a catastrophic failure, and so the clutch wouldn't engage unless refrigerant met an acceptable level.

Dean

[jopizz]

That's good to know because I thought the clutch wouldn't engage if refrigerant was low. I thought the system needed oil to prevent a catastrophic failure, and so the clutch wouldn't engage unless refrigerant met an acceptable level.

Dean

The original type compressors used in Thunderbirds had a separate oil fill port so you could add oil without discharging and opening the system. I believe manufacturers began installing cut off switches in the refrigerant lines back in the 70's. Obviously burning out compressors due to lack of refrigerant was a big problem. It was pretty much left up to the owner to check the sight glass and determine when it was low.

John

[torpedo]

A/C

Hello All, I'm new to the forum as I just picked up a time capsule 1965 Thunderbird. I bought it as having ice cold AC although after getting it home I find the compressor clutch not engaging. I jumpered the clutch and the compressor engaged so it seems it isn't getting 12V. The underhood wiring doesn't appear damaged anywhere, again its a low mileage not messed with car so hacked up wiring likely won't be the problem. I have the repair manual on the way but for now it seems it might point back the HVAC control in the console? Sound right? After jumpering the clutch the cold line did did cold and began condensating. The sight glass showed some bubbling so it seems it may be low. I couldn't pick up much in the way of cool air inside but again the refrigerant charge is probably too low.

Thanks in advance for any help!

I've run into this problem quite extensively, as the experts mentioned it could be the vacuum hoses (loose or cracked), if the compressor is not working check the compressor clutch line leading through the firewall underneath the console directly under the steering column or your switch part #19A945, mine had a damaged diaphragm (tiny hairline split) which I repaired after purchasing another. Both work fine. It can be repaired with patience when you know this part is hard to find. Hope this helps as I to am learning thanks to this forum.