66RBS

Re. 66 conv with factory air

On a recent 95* day I was cruising down the highway and noticed the following temps with the AC off. LH vent 115 -120. RH vent 105 -115. With the AC off and cool **** in the hot water shut off valve is closed and water is not flowing thru the heater. C2's rely on a door in the heater box to keep the hot air out of the cold air stream

So I thought I'd try a test to see where the heat is coming from. A few days later when the engine was cold I used two C Clamps to close both the input and output hoses to the heater. 82 * ambient and with AC off and cool **** in I was getting about 82 -84* temps at the AC outlets when engine up to temperature. I was figuring if I was getting engine heat thru the firewall it would show up with this test.

Stopped and removed the C clamps and on the return trip with AC off and cool **** in got temps of 98* LH and 94 RH AC vent. So it appears to me I am getting some heater leakage of about 15*.

Any ideas of how to reduce?

Randy

Nicola

Looks like the vacume control valve is not working.
When the valve is working properly it supplies vacume to the water valve which intern closes off the heater core when you call for cool. Top right cable us pushed in. When it is pulled out in the heat position valv supplies vacume which opens the water valve and floods the heater core.
Hope this helps.

Nicola

Sorry in heat position valve cuts off vacume which allows water valve to flood heater core for heat.

66RBS

You are correct. The cool in-hot pull ****,in addition to controlling the heat door, also controls the vacuum operated water valve which allows hot water into the heater core ONLY when this **** is pulled out. Above measurements were made with all ***** in.

So why would I get 15* of heat rise in the AC ducts if the hot water shut off valve and heat door is closed for all the tests? The only change was unblocking the 3/4" heater output hose with the C clamp. My guess is I am getting heat transfer to the heater core via conduction thru the 3/4" heater hose

Randy

65GGvert

I think the problem will be around the valve in the heater hose. It's either not closing securely, or the vacuum isn't correct.

65 Pro Vette

I bought a new A/C Delco control valve and tested it out of the car for leakage, it took 3 valves from the supplier to get a good one.

Powershift

I think you have a couple of issues here:

It sounds like a few internal doors are not working correctly as well as the hot water valve not closing all the way.

1. Pull the small hose off the hot water valve. This should close the hot water valve. Plug the end of the hose with a small screw or golf tee. When the car is hot, check the temperature of both heater hoses at the firewall connection. Both should be warm, but not hot if the valve is closing all the way. You can also check with an IR Temperature gun.

2. You should not have any air coming out of the AC vents unless you pull the AC on ****. This turns on the compressor and also opens the internal door to the AC vents. With this **** pushed in, the compressor should be off and the internal AC door closed. Any heat generated should come from the heater ducts.

The hot water valve is activated by a vacuum switch on the top of the heater box. These often good bad and leak thru. This may be the reason the hot water valve doesn't close all the way all the time.

Larry

Jud Chapin

Check to see if the weatherstripping on the rear of the hood is in place, and if so, is in good condition. If there is leakage here, hot engine compartment air will enter the HVAC system exiting the interior vents.

http://www.ecklerscorvette.com/corve...1963-1982.html

66RBS

I refinished the bottom of the hood about 3 months ago with fresh weatherstripping My plenum doors ( the oval ones in the footwells, unknown about the 4 internal doors in the heater box) are in good shape with fresh seals so even the hot outside ambient air shouldn't be entering the HVAC system

Randy

66RBS

Larry,

Pulled the vacuum hose off the hot water valve. With **** "cool in" in there is no vacuum (valve should be closed). With the **** "hot pull" out I got 15" of vacuum. So I guess my vacuum switch on the heater box is working. Reconnected vacuum line and idled with "hot pull" in out position ( valve should now be open). Turned fan on and felt warm air coming from heater ducts on side of radio panels

After about 5 minutes of idle

T Stat housing 165*
5/8" inlet hose before water valve 164*
metal valve body 167*
5/8" hose to heater 161*
return hose 3/4" 159*

The temp in the RH AC ducts were about 107* but started to fall when I pushed in the "cool in" ****.

I think I will let everything cool down and run the shut off valve temp tests tomorrow with the "cool in" **** in. Water valve should be closed so I'll see what temps I get. Also maybe I should remove glove box and see if I can determine position of "heat door" in front of heater

Randy

66RBS

Correct. I am just measuring the temps in the AC ducts with the AC off. I figure my AC has to overcome this additional heat (about 15*). I am just trying to Improve the efficiency

Randy

66RBS

Removed glove box to see what is happening with heater door. When the "cool in-hot pull" bowden cable is pulled it the pulls the lever to the door to the left opening the vacuum switch. All of this assembly is on a mounting plate that has slotted holes. I loosed the hex bolts and rotated the base approximately 3/16" clockwise hopefully moving the heater door more closely to a closed position in front of the heater. The mounting base rotates around the heater door shaft in foreground of picture. Retested to be sure the vacuum switch is still in adjustment; pull the **** yields 15" vacuum to the hot water valve.

Re ran the temp tests for the hot water valve with "cool in-hot pull" **** all the way in. Water valve should be closed. AC off and no fan.

T Stat housing 164*
5/8" inlet hose 126*
metal valve body 124*
5/8" hose to firewall 132*
3/4" return heater hose 125*
RH AC duct 77*

I am encouraged. Temps at the water valve are about 30* less so maybe the valve is closing and judging by the reduction in AC Duct temperature I may have closed the heater door. Time will tell.

Randy

Nicola

I also have a 66 factory A/C car.
With a/c off I have no air flow through the a/c ducts.
When the system calls for heat...temp cable out. This action should cut vacume to the water valve causing it to open and flood the heater core.
Am I correct?
Nic

66RBS

Partial credit. You had it correct in post #2. I had to edit my original post to correct the mistakes.

"When it is pulled out in the heat position valv supplies vacume which opens the water valve and floods the heater core."

See for yourself. Pull the vacuum hose off the water shut off valve. Cool in= no vacuum=valve closed
Hot pull=vacuum=valve open

Randy