'73 Water Valve: AIM vs TIM&JG

[Roger S.]

According to the TIM&JG a vacuum operated water control valve is installed in the heater hose: page 74. The AIM shows no valve in the hose installation area: page 128, section B01-B12 sheet 70. No valve is shown in the heater control schematic in the service manual either. Which is correct?
Roger

[Joe L.]

Re: '73 Water Valve: AIM vs TIM&JG

Roger-----

I don't think that 1973 Corvettes used a water control valve in the heater circuit for either A/C or non-A/C applications. Such valves were used with A/C applications on some earlier Corvettes (68-70) and were also used again after 1974 for both non-A/C and A/C applications.

[Bob Unkel]

Re: '73 Water Valve: AIM vs TIM&JG

My 73 is all apart and also didn't have a valve. I question how the hot water was kept out of the heater core when you wanted AC or just cool vent air? May explain why it was always so hot inside!

[Jack H.]

Re: '73 Water Valve: AIM vs TIM&JG

Answer: it wasn't.... The system as a 're-heat' design. AC made cold air through the evaporator and that was 'mixed' by doors controlling air flow across the heater core (some, all, none) to reheat the final makeup air flowing into the cabin.

The hot water shut-off valve was marginally effective from the git go. It's vac controlled and defaults to normally open. This means when you stop (lunch break, get gas), the engine isn't producing vacuum, the hot water valve opens and the heater core re-heats due to engine coolant convection.... Once you're back on the road and the valve re-closes due to engine vac, there's still residual heat in the heater core to contend with.

Eventhough the air flow baffles in the cabin A/C box direct air away from/around the heater core, there's plenty of residual heat 'soaked' into the air box! On stop & go trips, there's a learning curve with these cars....

Get back on the road after a stop and INTENTIONALLY run the A/C to soak residual heat out of the heater core & air box. Now the hot water shut-off valve will do its thing.

And, yes, there was a period of time when designers removed the hot water shut-off valve from Corvette (cost savings?)..... This was at the same time when fiberoptics went away, and we went from dual to single horn configuration. Eventually, the hot water shutoff valve returned!

[Bob Unkel]

Re: '73 Water Valve: AIM vs TIM&JG

Thanks Jack, I thought this was something else that was missing from my car. In a small way this adds to the cooling capacity of the radiator system. No wonder the AC seems marginal.