We have been taking all our fresh air heater cores to the same radiator repair shop for over 30 years now.
We found out that the old timer that runs the place will be retiring & selling the property.
This guy is the only guy that I have found that knows how to repair & pressure test the fresh air cores.

Since we knew his days at this shop are numbered.... we took all our heaters apart & had him repair & pressure test all of our cores.

We were lucky... we took him 4 cores at a time & he only charged us $20 to repair & pressure test them.... Our $80 investment neted us 16 good cores.



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Here is a good shot of one of our NOS heater control valves for reference.

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One note of caution regarding our fresh air heaters & control valves...
Our old radiator repair man said that the original cooling system is designed for a zero pressure radiator cap....
He stipulates no more than a 4 lb. cap is to be used with these original heating systems.