Pressure switches really need replacing or something else??

Hey guys, first post, new HVAC service technician here, only been doing service for a few months but had my license just over a year.

Anyways i ran into the same problem twice today on two different rheem R96V furnaces And thought I would run it by some of you guys.

Both no heat calls, show up for this is giving me error code 46 and 57 I believe, low pressure switch not closing in high fire mode and high pressure switch not closing in high fire mode. So first thing I do is hook up my manometer in the vent motor is pulling 1.8 inches WC, way above the 0.3 and 0.6 needed for low and high. But then after testing some more sometimes the pressure switches do close and the unit fires up.

Do pressure switches really go that often? Just seems weird that I run into two in a row in the same day, my company wants me in and out in a half an hour when we are subcontracting from these rental companies so I don’t get proper time to do a full diagnosis unless it’s one of our clients so I’m just told to write it down as replace the pressure switches and go from there.

Is there anything else worth checking if I run into that situation again? Just don’t want any callbacks

Check the ohm value of the pressure switch as well

You can always connect your meter to across the pressure switch in continuity mode and see if the switch is closing. If you want an excuse to buy another tool, you can pick up a SDMN6 pressure switch tester/manometer.

Also, a lot of those pressure switches are super cheap and the membrane they use for the differential is extremely delicate. I wouldn’t be at all surprised that you ran in to two defective pressure switches at rentals.

Originally Posted by WKenealey

You can always connect your meter to across the pressure switch in continuity mode and see if the switch is closing. If you want an excuse to buy another tool, you can pick up a SDMN6 pressure switch tester/manometer.

Also, a lot of those pressure switches are super cheap and the membrane they use for the differential is extremely delicate. I wouldn’t be at all surprised that you ran in to two defective pressure switches at rentals.

I can’t count the number of times a tech told me he checked the switch by blowing in it and it worked just fine.

Yeah but that tool doesn’t cost anything 🙄

Originally Posted by VTP99

Yeah but that tool doesn’t cost anything

I’ve had a few guys do it at the counter with a new switch. Sorry guys, If I see you do that, that switch isn’t getting returned under warranty.

Seems a bit suspicious that it’s pulling 1.8. Just seems really high compared to the labeled pressure.

Sent from my SM-S901U using Tapatalk

Originally Posted by 2sac

I can’t count the number of times a tech told me he checked the switch by blowing in it and it worked just fine.

They would blow IN to a pressure switch that measures negative relative pressure?!