Tapping the cad cell relay

Old 02-06-10, 07:47 PM
Thread Starter
Join Date: Feb 2010
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
Question Tapping the cad cell relay

I have an older furnace, runs well, but recently sometimes, not all the time, I have to tap the relay box on the furnace and as soon as i lightly tap it , it fires up, sometimes it will run good for awhile, sometimes I have to tap it again. Is it the relay, or cad cell, I replaced my thermostat and wasted that $20 bucks, trying to guess at it, a new relay is next at about 100.00, lol, or should I keep tapping???
Old 02-07-10, 04:39 AM
Join Date: Oct 2008
Location: New England
Posts: 9,460
Received 47 Upvotes on 43 Posts
Not that experienced with HVAC, but a lot with electronics. If a mechanical input produces a response, then the issue is mechanical. Relays can have contacts that are burnt to the point where they are not making contact and the tap helps, but not good to continue doing that as a solution. Circuit boards can have cold solder connections which develop over time that act the same way.

Whether a cad cell would react to the tapping or not, I can't say, but I would think it less likely.

We will see what the pros have to offer.


Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: