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Hello, I have a Honeywell thermostat that stop working recently.

It worked OK for at...
Hello, I have a Honeywell thermostat that stop working recently. It worked OK for at least the 5 years since I bought the place.

But now, no matter what temperature I set it to, when I turn it on, it works for about 10-15 minutes, then stops and never starts again, even though it's set to "auto" and the room temperature is much lower than 80 - it's about 65-68. I need to turn it off, wait 5-10 minutes and turn it on again, and even then it does not always start heating.

Should I just replace the thermostat? If so, what would be a correct replacement for the model I have - it's LR1620.

Thank you,
Natalie.
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Answered in 10 minutes by:
12/23/2010
Bill P.
Bill P., HVAC Mechanic
Category: HVAC
Satisfied Customers: 338
Experience: Oil / Gas / A/C / Hydronics
Verified

Bill P. :

hi there

JACUSTOMER-6grwkgmf- :

hello

Bill P. :

Did this just start recently or has it been acting up for awhile

JACUSTOMER-6grwkgmf- :

it started a few days ago, this week, it worked before OK.

Bill P. :

im just trying to find the manual for this thermostat, is it digital with batteries?

Bill P. :

from what i can find it is a older type, mercury thermostat, it that correct?

JACUSTOMER-6grwkgmf- :

no, it does not have batteries. it looks rather "old-fashioned". it's a brown box and there is a little handle on the left side to switch between "auto" and "on", and a little handle on the rigth to switch between "heat", "off" and "cool".

JACUSTOMER-6grwkgmf- :

it does have a mercury "thing" inside.

Bill P. :

Ok, they generally dont give too much trouble, we will have to figure out if the problem is actually in thermostat or elswhere

Bill P. :

does the bubble of mercury roll back and forth nice and easy, like bouncy

JACUSTOMER-6grwkgmf- :

but the heater itself works, it pushes the heated air for a while, but then it turns off.

Bill P. :

what type of heat to you have? gas with a/c, heat pump etc?

Bill P. :

and about what age is the heater?

JACUSTOMER-6grwkgmf- :

I am not sure about the type and age of the heater, definitely older than 5 years. I think it's gas with a/c

Bill P. :

ok it could also be a case of a sensor or something on the furnace is dirty and causing it to go off

Bill P. :

is the heat off right now?

JACUSTOMER-6grwkgmf- :

I am not at home at the moment. I normally turn on the heater in the morning, and turn it off at night. This morning the room termerature was about 62, and when I turned the heater on, it worked for about 10 minutes OK, then turned off. But it's set to "auto" and 90, and the room temperature was still around 66, and it did not turned on back again. Then I set it to "off", waited for 5 minutes, set it back to "heat" and the heater started again, but for another 5-6 minutes only. I have to repeat "set to off, wait, set to heat" steps in order to restart it.

Bill P. :

ok

Bill P. :

it sounds like it could be a problem with the furnace rather than the thermostat

Bill P. :

im not positive, i just dont want to say its the thermostat problem yet

Bill P. :

what you can do to be sure, is take the thermostat off the wall and unhook terminals R and W and wire them together

Bill P. :

that will bypass the thermostat and should make the heat come on and stay on.

Bill P. :

when you get home, go to your furnace and see if you can find a little sight glass in the fan door, and look through to try and see a flashing light

Bill P. :

that is if it is a normal gas furnace of15 yrs. or less..

Bill P. :

the blinking light is a diagnostic light and may give us a clue as to what is happening

Bill P. :

there will be a sticker on the fan door somwhere that explains what the blinking code means

JACUSTOMER-6grwkgmf- :

Ok, I'll try that. But in the case it's a thermostat problem, which current model should I purchase to replace the existing one? I don't need digital, so a mechanical one would be OK, but is there anything I need to check so that it works for the furnace I have?

Bill P. :

well if its just a normal system, pretty much and heat/cool stat will work

Bill P. :

i havnt been able to find a diagram of you current thermostat..

JACUSTOMER-6grwkgmf- :

Probably because it's old. Do I need to "accept" now or could we restart this conversation after I get home and check the furnace? I might have more questions then.

Bill P. :

you can leave it for now and it will email me when you come on and say hi again

Bill P. :

that would better i can then let you know if you just need a normal thermostat or not

Bill P. :

try looking for the blinking light first, then the jumper on the thermostat R and W terminals (unhook from thermostat first)

JACUSTOMER-6grwkgmf- :

Ok, thanks. But I'll need to use a different computer from home - how do I find you again? Do I go to this web-site and go to "My questions"?

Bill P. :

I guess so lol, Ive never been on that end of it..

Bill P. :

I believe so though yes

JACUSTOMER-6grwkgmf- :

Ok, I'll try to get back to you in a few hours. Thank you.

Bill P. :

Ok

Customer :

Hi Bill, let me know when you are available

Bill P. :

Hi

Bill P. :

Im still up wrapping presents..

Customer :

Sorry to bother you when you are busy with important stuff :-). I tried to find out what model if the heater I have - it's located at the attic of my townhouse, so when I finally manaed to climb there, I could not see any light inside the unit. It looks pretty old, though I could not find any date or year on it. The name isXXXXX it looks like there is a separate A/C unit there. The only number on the heater that I could see that looks like a model number is XXXXX if it means anything to you. Then I tried to turn on the thermostat again and it behaved the same way as before - the heater worked for a while, then stopped, then for half an hour or so nothing happened even though the temperature in the room is much lower than what I set the thermostat to, then I set it to "off", waited for a while and then set it to "heat" and it started again, then stopped after 5 minutes or so. Since now it feels warm enough in the room, I left it as is. So, I am wondering if it makes sense for me to try anything with the thermostat - if I disconnect it, it might not work at all after I connect it back and I won't be able to start the heater at all. Maybe I should just call some repair company and have them come over and check both the thermostat and the heater. What would you recommend?

Bill P. :

well if the furnace hasnt been looked at for quite awhile, it might not be a bad idea anyway

Bill P. :

how is the air filter? have you checked it lately?

Customer :

I replaced it a few days ago, so it's pretty new.

Bill P. :

ok

Bill P. :

Its up to you, you could try jumping the R and W at the thermostat, then you would know if it is the thermostat or not..

Bill P. :

but a service wouldnt hurt the furnace anyway, it may be a sensor needs cleaning or drains needing cleaned etc..

Customer :

How exactly do I "jump" the R and W? Do I do that when the main electicity switch is turned on? Or do I connect the R and W when the power is off and then turn it on? I know which switch on the main electrical panel controls the heater, so I could turn it off first if I need to.

Bill P. :

ther wires on the thermostat are low voltage and now dangerous, but you could turn the main power off so that you wont cross any wires and mess anything up

Bill P. :

so all you do is this, turn main power off, take thermostat off wall, (or flip it off, whatever it take to get to where the wires are) then take the wires off of R and W and touch them together

Bill P. :

or leave them connected to the thermostat (just put the thermostat to off first) and use a paperclip to connect R and W, its sometimes hard to get the paperclip to stay in there

Customer :

and does it matter which positions the thermostat controls are set to? There are two of them - one is called "fan" and can be switched between "on" and "auto", the other can be switched between "heat", "off" and "cool". Should I set them to "auto" and "off", respectively? While I was typing this, you sent another comment, so is this what I do - turn the power off, set the thermostat to "off", try connecting the R and W with a paparclip and then turn the power on?

Bill P. :

yes turn the thermostat to "off" and "auto" before you start

Bill P. :

the rest you have correct

Bill P. :

be sure that the paperclip is in there solidly

Customer :

OK, let me try this. By the way, which timezone are you in? Just curious how late is it for you?

Bill P. :

12:46 for me

Customer :

oh, you are on the East Coast, I suppose. I'm in LA and it's 9:47 here. I

Bill P. :

Yes Im in Ontario, easters time zone

Bill P. :

taking wires off and twisting them together is possibly easier for you..just depends what screwdriver you need..youll see when you flip thermostat off

Customer :

well, I managed to put the paparclip so that it stays by itself connecting the R and W, and the thermostat now is set to "auto" and "off", but the heater is working. So do I need to wait for some time to make sure it continues working?

Bill P. :

yes you need to see if it runs for longer than it has been, or till the house is quite warm

Customer :

but you know, there are no wires attached to the R and W - it's just two little ... hmm ... metal things coming out of the plastic marked with "R" and "W", so I just put the ends of the paperclip to them. There are wires - red, white and yellow - but they are connected to other things in the thermostat. Does it make sense?

Bill P. :

ok, i think maybe what you mean is you have taken the actual thermostat off the wall but the "sub base" is still on the wall

Bill P. :

the actual wires would be behind there

Bill P. :

it should work just as well the way is is

Customer :

well, I only took of the plastic cover of the thermostat, the rest is still there. I have not unscrewed it from the wall since like I said I was afraid that after that I would not be able to start the heater at all (and even though it's not too cold here in LA, still the temperature in the room drops to 63-65 without a heater, which is not comfortable).

Bill P. :

fair enough, I dont blame you, especially this time of year

Customer :

well, it stopped again, just like before. So what does it mean - something wrong with the heater itself?

Bill P. :

yes something wrong with the furnace then..

Bill P. :

since its working intermittantly, hopefully it just needs a good service

Customer :

It appears to be rather old, so it's possible nobody would want to deal with it - I am afraid they will just tell me to replace it, which will cost a lot ... Well, not much I can do about it. Thank you anyway, it's been good education for me. Merry Christmas and Happy New Year!

Bill P. :

ask around during Chrismas for a referall..i find personal referals to be much better than just calling from the phone book..

Bill P. :

Merry Christmas to you too!

Bill P.
Bill P., HVAC Mechanic
Category: HVAC
Satisfied Customers: 338
Experience: Oil / Gas / A/C / Hydronics
Verified
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Bill P., HVAC Mechanic
Category: HVAC
Satisfied Customers: 338
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