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No display on the thermostat and no AC

by The Handyguys

in Blog Posts, Handyguy Brian

Handyguy Brian had the following conversation, via instant messaging, with his lovely wife (or so he thought) about how to troubleshoot a no display issue with a thermostat and no Air Conditioning (AC). No audio here.

Some steps for troubleshooting your AC, thermostat or heat.

thermostat went blankBelow is an actual conversation. The initial assumption was bad batteries in the thermostat but we learned through troubleshooting that the particular thermostat doesn’t need batteries, read on and find out how we got the thermostat back on and the air-conditioning working. There is a surprise at the end!


Sarah: Is there a reason there is no display on the air conditioning controls? It’s hot in here and I wanted to turn it on. It’s blank.

me: probably the batteries are dead in the thermostat. The cover should just pop off and I think 2 AA batteries.

Try that first. If that doesn’t bring it back to life we can then check the electrical panel for a tripped breaker. If that’s not it there are a few other things we can easily check.

Sarah: no batteries

there r no batteries

me:  you sure??

Sarah: yes

me: hmmmmm

check the breaker box, there should be a breaker labeled AC or hvac or something, flip it off and then back on.

it’s probably a double breaker.

Sarah: ok brb

Sarah: nope didnt work

me: If that doesn’t do it, tell me what model number & manufacturer of thermostat we have

Sarah: i have no idea

me: It should say on the cover or something

honeywell xyzpdq123 or something

Sarah: the front says: White-Rodgers

me: okay, and a model ##?

Sarah: there isnt one on the front

me: k, hold on a min…

me: Model number should be on the inside of the front cover.

Sarah: u mean the “type #”?

me: yes

Sarah: 1F86-241

me: reset the thermostat by pressing <up>, <down> buttons and move the SYSTEM switch from OFF to HEAT at the same time.

Sarah: k but we want cold air

me: please do exactly that ^^^^

Sarah: k then do i put it to cool?

me: just do that and tell me if the display comes on

Sarah: kk

me: You are pressing and holding BOTH up and down buttons while moving the switch from off to heat

Sarah: i did that and it didnt work

me: okay, do these things…..

1) Double check all the breakers, turn every one off then on…

2) check the emergency shut-off switch at the top of the basement stairs, make sure someone didn’t mess with it.

Sarah: all of them?!

me: ALL of them

Sarah: the breakers


me: all of them

one at a time

Sarah: fine then check emergency switch?

me: yes, then….

3) check the service disconnect switch, it’s mounted on the side of the main unit in the basement, it’s a normal looking switch.

Sarah: k ill start with the breakers


me: make sure no one messed with it, it should be on.

4) check the service access panel, it’s the cover that faces the red couch. There is a switch behind the cover that turns off the power if it’s removed. Make sure that cover is secure.

me: 5) In the basement, near the service disconnect switch, look for small thin wires, do they look like someone was messing with them? Maybe someone was putting something in that closet and knocked them and pulled one loose?

Sarah: what main unit?

the red switch is on i flipped and flipped all the circuit breakers one at a time so what is the main unit that has the normal looking switch

what is the main unit?

me: In the basement closet, the big beige thing

that all the ducts are connected to.

did anyone put stuff in there and maybe bumped the switch?

Sarah: ooo that thing kk brb

Sarah: nothing is in there that might have bumped it but it was off so i turned it on

me: hmmm, someone messed with it

did that fix the problem?

Sarah: yes thx u

me: whew

Sarah: now the house will get cooler



me: one of the kids switched it

Sarah: y would they do that?

me: just to see what it would do

maybe they thought they would be turning on a light

A few minutes later…

Sarah: That was your daughter you were chatting with. I’ve been one the phone!

me: ahahhahah

she did all that?


Sarah: ye


me: hahha

toooooooooo funny

me: I want to make a post from the chat! Its good info

Sarah: You are funny. ;)

How about that! Handyguy Brian’s 13 year old daughter was able to fix the air conditioning!

This is blog post only, no audio podcast.

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{ 20 comments… read them below or add one }

Sarah Hill June 21, 2011 at 3:15 pm

Funny! We have those conversations with people everyday. Good thing we know so many great servicemen to help them out. Thanks for sharing!


Jay July 14, 2012 at 10:19 pm

I went through all those steps and then saw that the drain hose came unhooked from the unit and the catch basin had filled with water. After I bailed enough water out, the unit restarted.


The Handyguys July 15, 2012 at 5:06 pm

Good catch – Just make sure the drain is not clogged and the pump is working so you don’t have the issue again.


Michelle Gates November 24, 2012 at 10:52 am

I followed these steps and figured out that the batteries were dead. I then had to reset the thermostat. Thank you for saving me a service call.


Maria May 26, 2013 at 9:29 am

Y air conditioner stop working . I have a white roger s rectangle model about eigh yrs old in an condo apt . All off the sudden my unit started making nose and no air was blowing . I had a very bad burning smell coming out off my vents. I shut the brakers on an off then inside to the unit an handle with on an off I then shut that on and off . The unit still does not work . Please help


The Handyguys May 28, 2013 at 9:33 am

This sounds like more than a thermostat issue. I would suggest calling a AC repairman.


murali June 28, 2013 at 4:56 pm

I have this honeywell model # CT3600A4444 thermostat and it stopped displying i tried all above steps tried to restart all circuits and changed batteries but LCD still doesnt work. When i turn that i do get the air off the vents but airconditioner outside still doesnt turn on ..any suggestion?


The Handyguys June 29, 2013 at 10:00 am

Either a bad thermostat, bad wire between the thermostat and AC or a bad control board in the AC. New thermostat is easy to swap out to see if that’s the issue. Return it if it doesn’t work and call a repair company.


maria September 23, 2013 at 2:21 pm

my thermostat is not displaying the temperature just HL what does that mean?


The Handyguys September 24, 2013 at 9:01 am

HL probably means High Limit. It sounds like you are in a service or configuration mode. Try removing the battery (if you have one) for a minute or so then re-install. If it still says HL, try new, fresh, batteries. If that doesn’t work post the manufacturer and model number of the thermostat (Or google them) and see if you can find an owners manual to look up what may be wrong.


ralph a. applegate October 29, 2013 at 4:42 pm

My thermostat was off and so was the furnace . I put in new batteries and it still did not work. I did not check breakers because I did not see how that could disconnect?


The Handyguys October 31, 2013 at 2:08 pm

It indeed could be a breaker or fuse. Check those before calling for service.


scott November 24, 2013 at 2:27 pm

I have a have tried all of the mentioned steps, put batteries and the display light up. Once I removed the batteries the display went blank



izy January 25, 2014 at 5:46 pm

ok i am having aproblem with the ac. i tried to replace the batteries and when i put the lid thing back on it wouldnt fit right. while i was trying to fix it to fix it fell and the battery holder popped off. i stuck it back on. now when i try to put the lid back on two things happen. first either the light turns on and i can see the buttons if its not on correctly but the ac wont turn on, or i put it in correctly the ac turns on, but i cant see the display. please tell me what i can do as when i just make the ac work it stays stuck on 67 which is way too cold.


Inita February 5, 2014 at 11:24 pm

Wow. My thermostat also had no display on the air conditioning controls. On your advice I replaced the batteries. IT WORKED. FEELING GOOD NOW! Thank you.l


D.Sant February 25, 2014 at 1:01 am

My Honeywell thermostat THM5421 had a blank screen when the water pump stopped working. The thermostat controls a 95% efficient furnace. The water pump filled up and did not empty automatically. When I manually emptied the water tank in the pump the thermostat started working again. For a permanent fix the pump had to be replaced. A furnace technician offered to replace pump for $500, but I found the identical pump on Amazon for $50 and did it myself.


The Handyguys February 25, 2014 at 8:27 am

Good job!


Chris March 4, 2014 at 9:34 pm

Thermostat said I needed battery. Replaced them and now AC is on and when I put the thermostat to 75 it stays on 77 and no cool air coming out vents. The icon for the battery is still in the panel, not the battery pic but a circular icon.


The Handyguys March 5, 2014 at 12:02 pm

The circular icon probably means fan. The battery icon probably indicates a full battery. It sounds like one of two issues. My first thought is you have only the fan turned on. Check if you have a switch that says Auto<>Fan or AC<>Fan, make sure its in auto or AC position. If it is, perhaps a wire became disconnected when you changed the battery. If none of those then you could have a defective thermostat or your AC has a freon leak.

If this is the first time you tried to use the AC in a while I would lean towards a Freon leak.


Mike April 10, 2014 at 3:25 pm

The house I’m renting just had both thermostats die like this overnight. I read the whole post and found a light switch in the attic that I turned off then back on and it worked. Thanks!


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