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: 22629
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

Honeywell Thermostat Saying “HOLD-AC”.

Customer Question

My Honeywell programmable thermostat says "HOLD-AC". What does that mean?

Submitted: 6 years ago.
Category: HVAC
Expert:  BillyHvac replied 6 years ago.

Thank you for choosing JustAnswer! This most commonly means the thermostat is missing A/C power. The furnace is not sending power to the thermostat. What is the make/model of the furnace?

Customer: replied 6 years ago.

I am not at home now and will have to check.

Expert:  BillyHvac replied 6 years ago.

Okay, here is a test.

Remove thermostat from top wall mount plate. You will see thermostat wires attached to lettered terminals. Locate R and G, then use a paper clip shaped in a U - touch one end to R while touching other end to G. If the fan/blower starts, it is a thermostat issue. If the blower does not start, it is the furnace not sending power to thermostat.

A blown fuse on the circuit board in the furnace, a high water safety switch, and the main power to furnace off are the biggest culprits.

BillyHvac and 2 other HVAC Specialists are ready to help you
Customer: replied 6 years ago.

Our furnace is a Rheem Criterion II. I checked the R-G jump as suggested and got nothing to happen. I changed out the hot surface igniter (just in case) and no change. The breaker is on and when I operate the switch on the furnace I can hear a "hum" when it is in the "on" position that stops when I switch it to off, so I'm pretty sure I have power to the furnace.

Expert:  BillyHvac replied 6 years ago.

Have you checked the small fuse on the circuit board? It is located in the blower section.

Customer: replied 6 years ago.
How do I find the fuse? I looked and failed to locate it.
Expert:  BillyHvac replied 6 years ago.

If you can get me the model number of the furnace I can be more specific.

Also are you running heat or air? If in A/C use, there can be a blocked drain switch that shuts power off to thermostat.

Get me the model and we can move forward.

Customer: replied 6 years ago.

Rheem Criterion II. We had central air installed a couple of years ago on the upstairs furnace. This issue is with the heat from the basement furnace, but with the AC installation we had a humidifier installed on the basement furnace and it has a drain tube on it. We have not run that humidifier much, and I have noticed some "stuff" in the clear drain tube. I will go home and look. I am at work right now. I will also look in the lower panel for a circuit board with a fuse on it.

Expert:  BillyHvac replied 6 years ago.

Thank you, ***** ***** you can get the model number of which Criterion; it will start with a RG, then other numbers. Then I can you specifically where to check. There various models and that number will give us direction.

Customer: replied 6 years ago.

It is Model RGDG-12EARJR

I have removed the lower panel cover and cover on the circuit board and can't find a fuse. The humidifier is dry; dusty and cruddy but dry.

Expert:  BillyHvac replied 6 years ago.

Thank you, ***** ***** RGDG the fuse is in the wire that leads from the transformer to the circuit board. It is an inch long and a small tube inside a capsule. Also, tape door safety switch down and see if the circuit board blinks a sequence of lights.

Customer: replied 6 years ago.

Found the fuse. It is burnt. It seemed I needed a pocket microscope to see it. Man, that dude is little. Any idea why it would burn?

Expert:  BillyHvac replied 6 years ago.

The biggest culprit is the outdoor thermostat wire to ac unit damaged, check that wire before turning power back on, or do not hook up Y and C on circuit board.

Customer: replied 6 years ago.

I replaced the fuse without really expending a lot of energy in looking for the reason for it. I guess I'm hoping it was an isolated incident; like a lightning strike, or something during the summer months while it was not being used. It was very difficult to find a replacement for the fuse. None of the vendors I checked with had the right size, voltage and amperage combination. I ended up replacing the fuse holder with one that fit the 250V 2A requirement, and used an off the shelf size from radio shack. Thank you for your help. The furnace was still working this morning, so whatever caused the fuse to blow has not been repeated (so far). I did buy spare fuses, just in case.

Expert:  BillyHvac replied 6 years ago.

You did the correct thing; replace with fuse and holder readily available.

I appreciate the cooperation and competent help, well done.