[Sport71]

All,

We've been having some cold mornings lately, so I'm trying to get my ThermAC valve to function properly (71 LeMans Sport / 350). The air cleaner is a single snorkel type. On cold starts the valve is not closing in order to let the heated air from the exhaust manifold to the carb. I thought that the air temperature sensor that sits in the air cleaner was bad, so I replaced it with a new one. Still no movement of the valve. When I hook up vacuum directly to the valve it moves to the correct position, so I know it's not seized up or the diaphragm isn't bad. I bought a second air temp sensor (thinking the first might be bad) and the problem remains. I figure the chances of 2 brand new sensors being bad is slim (right?!). I've been running vacuum from the port directly forward of the carb to one port of the sensor, then from the second sensor port to the ThermAC unit. Any suggestions?

Thanks guys ...

Vince

[Sport71]

All,

We've been having some cold mornings lately, so I'm trying to get my ThermAC valve to function properly (71 LeMans Sport / 350). The air cleaner is a single snorkel type. On cold starts the valve is not closing in order to let the heated air from the exhaust manifold to the carb. I thought that the air temperature sensor that sits in the air cleaner was bad, so I replaced it with a new one. Still no movement of the valve. When I hook up vacuum directly to the valve it moves to the correct position, so I know it's not seized up or the diaphragm isn't bad. I bought a second air temp sensor (thinking the first might be bad) and the problem remains. I figure the chances of 2 brand new sensors being bad is slim (right?!). I've been running vacuum from the port directly forward of the carb to one port of the sensor, then from the second sensor port to the ThermAC unit. Any suggestions?

Thanks guys ...

Vince

[george kujanski]

Are you sure the port you are using has manifold vacuum rather than ported vacuum? Sounds like that's the only thing it can be since your connections sound right.

Regards, George

[Sport71]

George,

Thanks for the response. The vacuum source that I'm using is right in front of the carb on the intake manifold, so I'm fairly certain that it's of the correct (vacuum) type. The only other vacuum-driven items are already hooked-up and working fine (PCV, distributor advance, transmission line).

There isn't some other device that goes between the manifold source and the air temperature sensor, is there? If someone has a schematic of the vacuum line routing it would really help. Thanks again ...

[fiedlerh]

Heat it with a hair dryer and test it with a MityVac hand pump or engine vacuum. It should actuate around 150°F and can be adjusted if it is off. Use a small pin punch in the nipple and a pair of pliers to turn the nipple. The pin punch prevents you from collapsing the tube.

[Sport71]

Great idea. I didn't realize that adjustments could be made on the sensor. I'll try it this weekend. Thanks.