1965 AC Question

**Motormitch** · 08-20-2012, 08:05 AM

I just picked up a barn find 1965 Riviera and got it running and brakes working this weekend. It has a factory AC system on it and it is intact. Clearly after setting for quite a while, it had no gas in it, but the compressor still engaged when turned on so I thought that I would put some in it just for kicks to see if the system would hold gas. I found what I am pretty sure was the low side access port and started injecting. Right above the access port is what looks like a vacuum actuator and when I turn on the gas, it blew the small vacuum line off of it. Then I tried again and this time the line stayed on, but gas began to leak out around the base of the connector for the actuator (bolted together with 4 small screws. What the heck is this and am I even using the right access port on the AC system? I have never seen anything like that before, but I have spent most of my time with Mustangs, late 60's Toronados. Anyone have a diagram of the AC system showing the different components?

Second question, When I drained the gas tank I also replaced the fuel filter at the engine with a clear one to watch the gas and I noticed that the factory one it had one line in and two lines out. One to the carb and then a return line to the tank. When I looked the part up to see about ordering a new one, I found that there are two fuel filters. one only has one line in and one line out and the other looks like the one on the car with one line in and two lines out. It lists the one for one as a Non AC car and the other as a part for cars with AC. I have be showing my ignorance, but why would the presence of an AC system require a fuel filter with a return line (or return line to be more clear)

THanks in advance for any help....

**raycow** · 08-20-2012, 02:40 PM

When the AC is in operation, the underhood temperature is likely to be higher than with no AC. The purpose of the fuel recirculation system is to lower the fuel temperature in the engine area and hopefully prevent the fuel from boiling and causing vapor lock. Also, if vapor bubbles do form, at least some of them might get returned to the tank.

Sorry, but can't help you with the AC problem.

Ray

**Motormitch** · 08-20-2012, 06:55 PM

Originally Posted by raycow

When the AC is in operation, the underhood temperature is likely to be higher than with no AC. The purpose of the fuel recirculation system is to lower the fuel temperature in the engine area and hopefully prevent the fuel from boiling and causing vapor lock. Also, if vapor bubbles do form, at least some of them might get returned to the tank.

Sorry, but can't help you with the AC problem.

Ray

Thank for the explaination/ It makes perfect sense and helps explain it. I have struggled with vapor lock on my 67 GT390 Mustang becuase it has every option possible and is running a 428CJ so here in Texas it gets HOT. I put in an electric fuel pump with return line and the problem basically disappeared.

**Bob** · 08-20-2012, 09:40 PM

I don't think there should be any vacuum lines blowing of the a/c system when charging it...

**Motormitch** · 08-21-2012, 05:19 AM

Originally Posted by Bob

I don't think there should be any vacuum lines blowing of the a/c system when charging it...

This diagram really helps me to understand the flow. Thanks a lot. I have ordered a set of shop manuals for exactly this type of help. The vacuum line that was blowing off is the one going to the suction throttle valve. That must mean that the part is REALLY shot to let the gas push all the way out of the vacuum valve. Does anyone know where I can get a new/rebuilt valve?

Thanks,
Mitch

**Bob** · 08-21-2012, 07:02 AM

Old Air has STV kits:

http://www.oldairproducts.com/catalo...iera&Year=1965

Or these guys might do a restore on yours:
http://www.classicautoair.com/GM_OEM_Parts_Valves.html

**Motormitch** · 08-21-2012, 08:48 AM

Originally Posted by Bob

Old Air has STV kits:

http://www.oldairproducts.com/catalo...iera&Year=1965

Or these guys might do a restore on yours:
http://www.classicautoair.com/GM_OEM_Parts_Valves.html

THis is a great forum and thank you to everyone for thier help. One last question (I hope) on the STV issue. If I am not trying to do 100 point show car restoration, but just an awesome weekend driver, would you rebuild the STV or covert to an electric clutch control? Also, if converting to 134a, the STV needs to be calibrated, but is it safe to assume that the calibration issue disappears if you convert to electric clutch?
Mitch

**telriv** · 08-21-2012, 04:57 PM

Some may disagree, but this is MHO. A vehicle designed for R-12 needs to remain R-12. To use 134 the A/C condenser needs to have AT LEAST a 25% larger capacity to properly cool. 134 runs at higher pressures & the original hoses were NOT designed to hold these kind of pressures. Also you need the newer hoses which are NOT as porous as the orugunals. Lastly, the original A/C compressor was NOT designed to cycle on & off. All the O-rings need to be changed along with the compressor seals as well as the receiver/drier. I know some have converted to 134 & had great results, but I REFUSE to do this in my shop.
Again, just MHO.

Tom T.