How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask BillyHvac Your Own Question
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 21998
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
Type Your HVAC Question Here...
BillyHvac is online now
A new question is answered every 9 seconds

I have a new Rheem package unit. It seems to be losing the

Customer Question

I have a new Rheem package unit. It seems to be losing the 24v. My contactor is going In and out. I've checked the voltage and its dropping from 24v to 10 or 12 ,8 it jumps all around.
Submitted: 4 months ago.
Category: HVAC
Expert:  BillyHvac replied 4 months ago.


at the unit...where thermostat wires attach...jump R to Y...tell me if the contactor stays closed or chatters

Customer: replied 4 months ago.
I jumped r and y and yes it still chatters. I removed everything that's is in the loop. Thermostat, smoke detector, economizer. And bypassed it jumping r and y and it does the same thing. I changed the transformer and the circuit board and still the same. I removed the low voltage wires from the contactor thinking it might be a bad contactor when under load. And checked voltage on wires and getting the same thing. 24v dropping to 10v, 8, 12 and the board starts clicking.
Customer: replied 4 months ago.
It's a new install which was running for about 2-3 weeks just started having problems.
Expert:  BillyHvac replied 4 months ago.

did you by pass everything on the y side and send thermostat wire (Y) direct to contactor thus eliminating lps, hps, delays etc...just to start elimination?

Customer: replied 4 months ago.
bypassed all pressure switches.
Expert:  BillyHvac replied 4 months ago.

I understand but to draw a firm line for direction...did you actually put the Y wire from thermostat direct to contactor

Customer: replied 4 months ago.
still does same thing
Customer: replied 4 months ago.
I checked directly off the board and same. It's acting like a bad board but I just replaced it. Also if I jump R and G the board starts clicking but nothing comes on.
Expert:  BillyHvac replied 4 months ago.

Thank you.

Is the transformer wired for proper input as 208 or 230 depending on present voltage?

And is this single phase or 3 phase

Customer: replied 4 months ago.
its a 3 phase and yes it's wired for proper voltage. I tried it on both 208 and 230 and same thing.
Expert:  BillyHvac replied 4 months ago.

is there a stinger?

Customer: replied 4 months ago.
Customer: replied 4 months ago.
In compressor compartment. It had some build up around it. Sort of what builds up on a car battery terminal.
Expert:  BillyHvac replied 4 months ago.

I ask because I was called by a manufacturer to troubleshoot a similar situation that I found the wild leg was controlling the transformer.

Once I moved the wild leg from supplying the transformer all was well.

Was the corrosion on the compressor terminals themselves?

Customer: replied 4 months ago.
No just around it.It was working fine for a few weeks
Expert:  BillyHvac replied 4 months ago.

well I dont think it is board,

as a test you can run direct 24v to contactor from thermostat, no board..nothing but transformer feeding contactor coil..if it still chatters then you will need to look at supply voltage/ground issues.

The beauty of transformer direct to contactor is it takes everything out of equation except 24v start and end.

Customer: replied 4 months ago.
I'll try that but if it dosent chatter when run I g from transformer to contactor directly then I'm back to where I'm at.
I disconnected wires from the transformer and checked voltage at transformer and it held 24v so I'm pretty sure when I connect it to the contactor it should work that way. But then what?
Expert:  BillyHvac replied 4 months ago.

By your have tried everything else.

You said you bypassed the entire 24v that is eliminated as it still faults

That leaves 230 supply and 24v output...what controls output is the supply.

Bypassing direct to contactor, which is new is not going to ground or cause 24v issue.

So when you say "then what"...I do not know as my next move is contingent on what I find each step of the way.

Right now you are painted in a corner with supply voltage and 24v as suspect..

Have you unhooked loads on the 230 side to see transformer reaction?

Customer: replied 4 months ago.
Thank you. I'll try that tomorrow.
Expert:  BillyHvac replied 4 months ago.

Take another contactor...unhook the 24v from the existing..put it to the one in your hand...the loads wont engage as the contactor in the unit stays open...

If the contactor in your hand is definitely supply/ground related.

If it does NOT....then you know that there is possible draw from a load affecting the power supply..and remember to check for the wild leg feeding transformer..

also you can remove compressor from contactor and see if fan only still makes it can remove fan same way.....right now I would look at high voltage side

Customer: replied 4 months ago.
That makes sense. I'll try that for sure tomorrow. Thanks again. I'll let you know tomorrow what I find.
Expert:  BillyHvac replied 4 months ago.

Just keep me not respond to this message until you have info...any response makes the computer system force a response from just wait until you have news...good luck


Customer: replied 4 months ago.
Good morning. Took another contactor and installed the 24v side only. Still does the same contactor goes In and out.
Expert:  BillyHvac replied 4 months ago.

did you switch the power feed to the transformer once you narrowed this down?

It is now down to power feeding the transformer, transformer ground, unit ground, wild leg.

Related HVAC Questions