Air Cleaner Temp Sensor Problems

[this 'ol truck]

 

Working on a '74 C20 with just over 30K on the clock. After replacing all the hoses, belts and major tune-up, I find that the Thermac flap quit opening up in the air cleaner snorkel. I replaced the temp sensor and it still won't open after warming up. The truck is bone stock original other than 2.25 in duals/w turbo mufflers and a '88 air cleaner minus the screen like restrictor. I bought a US made sensor but i guess it could still be faulty, it just doesn't add up. Any ideas would be a big help.

[txab]

The default position should be "open". Another words, with no vacuum applied to the damper motor it should be open. Are you sure it isn't stuck closed?

[kuhl_530]

Maybe a fault in the wiring to the sensor?

[txab]

Maybe a fault in the wiring to the sensor?

It should be totally vacuum operated. This is a 1974 model

[this 'ol truck]

Working on a '74 C20 with just over 30K on the clock. After replacing all the hoses, belts and major tune-up, I find that the Thermac flap quit opening up in the air cleaner snorkel. I replaced the temp sensor and it still won't open after warming up. The truck is bone stock original other than 2.25 in duals/w turbo mufflers and a '88 air cleaner minus the screen like restrictor. I bought a US made sensor but i guess it could still be faulty, it just doesn't add up. Any ideas would be a big help.

 

tested the vacuum motor and it opens and closes just fine.( just dissconected the vacuum hose and reinstalled)

[txab]

So the door opened when you removed the vacuum source? If that is the case then you should try another sensor in the air breather. Again the default position is for the door to be open when no vacuum is present

[Mike G]

Let me get this straight.. The 72 air cleaner should be vacuum operated, I would guess it works like all other so that when vacuum is decreased by excellerating, the flap opens to allow more air. If the air cleaner is from an 88, should that not be temp regulated and opens the flap when it gets warmed up, much like a "automatic" choke?

[this 'ol truck]

Let me get this straight.. The 72 air cleaner should be vacuum operated, I would guess it works like all other so that when vacuum is decreased by excellerating, the flap opens to allow more air. If the air cleaner is from an 88, should that not be temp regulated and opens the flap when it gets warmed up, much like a "automatic" choke?

 

 

that's it. the sensor closes off the vacuum when it reaches running temp. going to try another new one ASAP.

[Mike G]

What part of the country you located in and do you need air restriction? I block my air cleaner restrictors open on my toys, since they are usually driven in the summer anyway.

--Mike

[this 'ol truck]

What part of the country you located in and do you need air restriction? I block my air cleaner restrictors open on my toys, since they are usually driven in the summer anyway.

--Mike

 

just like the cold warm up feature, even though i do live in the same neck of the woods (Centennial) got the new sensor in and she's running like new once again. I drive it to and from work and to haul or tow, that's it.

[Mike G]

Well howdy neighbor!