C2 or C3 with C60 test

[Harry S.]

Since it's been hot this week I was wondering if anyone with a C2 or C3 and an IR gun could run a heat test for me. I'm interested in the temperatures on the input side and output side of the hot-water-shutoff valve.

Take you car for a run with the AC on, stop, leave it running with the AC on and check the temp on the input side and the output side of the hot-water-shutoff. On the output side check as close to the firewall as you can get.

I believe my hot-water-shutoff is stuck a bit open and is sending hot water into the heater core all the time. The affect is to warm all that nice cold air generated by the AC unit. My freon is OK, already checked that.

Thanks

[Stuart F.]

Re: C2 or C3 with C60 test

I'd be glad to help you Harry, but I have the 2W/Tx60 A/C system, i.e. 2 windows and top down x 60mph.

Stu Fox

[Jim T.]

Re: C2 or C3 with C60 test

Harry I am not sure about a C2, however on the 1969 and 1970 C3's the only time the vacuum valve is activated to shut off coolant to the heater core in the air conditioned Corvettes is when MAX is selected on the selector dial for air conditioning. If the selector dial is not on MAX there is coolant flow through the heater core. This is one reason why since it was new I have always select MAX when I am using air conditioning in my 1970. MAX recirculates air from inside the car, outside air is not used.

Looking at my 1964 supplement service manual it says the "COOL IN-HOT PULL controls a vacuum switch (operated by the temperature door actuating door cam) controls a vacuum water valve which allows engine coolant to flow through the heater core only when this knob is pulled out."

[Harry S.]

Re: C2 or C3 with C60 test

Harry I am not sure about a C2, however on the 1969 and 1970 C3's the only time the vacuum valve is activated to shut off coolant to the heater core in the air conditioned Corvettes is when MAX is selected on the selector dial for air conditioning. If the selector dial is not on MAX there is coolant flow through the heater core. This is one reason why since it was new I have always select MAX when I am using air conditioning in my 1970. MAX recirculates air from inside the car, outside air is not used.

Looking at my 1964 supplement service manual it says the "COOL IN-HOT PULL controls a vacuum switch (operated by the temperature door actuating door cam) controls a vacuum water valve which allows engine coolant to flow through the heater core only when this knob is pulled out."

Jim, a 63 is like the 64. no coolant until you pull the lever for heat.

Think I found the bug today and it wasn't the hot water shutoff. Took the car for a 5 mile ride and all I got was slightly cooled air. When I got home I let it run and put the IR gun on the hot water shutoff valve.

Then the freon hose blew off the tube that goes to the cooling coils in-front of the radiator. This tells me the problem is the STV is out of whack as there was no balanced pressure from the hi and low sides.

Off to fix another problem........

[Don H.]

Re: C2 or C3 with C60 test

Harry, I had my '65 out today with the AC on but had not yet read your post to answer the question. For what it is worth, I always pull & plug the vacuum line to the shut off and the valve inlet during AC months. I then plug it back in during cooler months. This method is not good for a PV but works well from a practical stand point. Don H.

[Jim T.]

Re: C2 or C3 with C60 test

Don my understanding from reading my 64's service manual is that your procedure allows circulation of hot coolant through the heater coil 100% of the time when the vacuum line is disconnected from the shut off valve.

[Don H.]

Re: C2 or C3 with C60 test

Jim, I do not think that is correct. I believe the valve is spring loaded closed and the vacuum opens it. I have done this for years with a '64 I used to own and my present '65. I can currently hit the low 40 degrees F at the vent with my '65 with the air on. The 1964 and 1965 air units are virtually identical. Good luck, Don H.

[Harry S.]

Re: C2 or C3 with C60 test

Jim, I do not think that is correct. I believe the valve is spring loaded closed and the vacuum opens it. I have done this for years with a '64 I used to own and my present '65. I can currently hit the low 40 degrees F at the vent with my '65 with the air on. The 1964 and 1965 air units are virtually identical. Good luck, Don H.

Correct, the valve is closed all the time. It opens with as little as 5 inches of vacuum.

[William F.]

Re: C2 or C3 with C60 test

Most all of these hot water valves let some hot water through even when in "closed" position. Won't judge, but many put a cutoff valve in the inlet hose a few ins. before it enters firewall

[Harry S.]

Re: C2 or C3 with C60 test

Just an FYI. I've attached a picture of the hot-water shutoff where it is dated.