Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Bryant 350mav pressure switch issue

swayze19 Member Posts: 3
I recently went on a job for side work, I typically don't but they're family and it's November. The original call was a roll out switch, furnace is 11 years old and never seen service, apparently never had issues, so flame roll out led me to a cracked secondary heat exchanger I just replaced it got it all back together and the thing won't fire. The pressure switch wouldn't make. In turn I take all nessary measurements and I saw it run with a lazy flame until roll out kicked. If I blow into tubing I can hear it make yet when I jump out the pressure switch it runs perfect. Ran a combustion test and all numbers are good. Pulled tubing off to inspect and found what looks like peices to a restricter in the tubing and pressure switch. Took it all out re attached and nothing. Jumped pressure switch runs until it makes temp then you have to pull it off and put it back on when it calls. Left unit off until I can figure this one out.


  • mars_6
    mars_6 Member Posts: 107
    Did they have a new roof installed this summer?
    Matt Rossi
  • swayze19
    swayze19 Member Posts: 3
    No I don't think so
  • unclejohn
    unclejohn Member Posts: 1,830
    Your numbers can't be good if the switch won't make and it still trips the roll out when jumped.
  • swayze19
    swayze19 Member Posts: 3
    I think I may have misspoke it was tripping on roll out when I found it, that led to a cracked secondary heat exchanger, that was replaced and everything put back together, when I went to refire it it was out on the pressure switch, I took a bunch of measurements and jumped out the switch, at that point I used a combustion analyzer to see how it was firing all the numbers were good, when I returned today I replaced the pressure switch and still same thing, all tubing looked in tack but I didn't have ten properly connected to the collector box and condensate, the labels on the tubing read the same directions and that was the mistake, once I switched were i landing the tubing it fired on its own and only shut down when the stat was satisfied. Thanks so much for your input and I'll be here again I'm sure