[Zerox1969]

Each year when it gets cold, my Gas Air Conditioner won't start when its to cold out. I turn the thermostat up, the unit clicks but then doesn't start right away. Sometimes it won't start until the sun hits the air conditioner. Last year I replaced the valve and cleaned the flame sensor. From what I have read the limit switch needs to heat up to a certain temperature before the blower relay will start the blower.

I am wondering if my fan / limit switch is bad? Or is the blower relay bad? Any suggestions.

I have had three repairs guys come out over the years, but its always working by the time they make it out and they can't find anything wrong.

Thanks...

[hvac1000]

Your unit could have a low temperature cut off. Are you running the unit in the A/C or heat mode. I would like to add that I have not seen one of those in our area for years.

[Zerox1969]

I am running in Heat Mode. I have that exact Camstat Fan & Limit Control unit you have posted in the sticky notes.

Also this morning I hooked up a new digital thermostat. I did this years ago, which did not help. But I thought what the hell. When I turn this new thermostat up, I do get feedback telling me that the heating system is running, but it still doesn't fire up for quite some time.

Another question, what is telling my electronic thermostat that it is running? Is that the camstat or the flame sensor?

Thanks for the help!

[labman]

Does the system have a schematic posted on it anywhere? Sometimes if you can't find an experienced repairman, you have to rat things out yourself.

[hvac1000]

Your thermostat is just telling you that the signal is sent to the unit. The thermostat has no way to verify that it is actually running.

You can jump the camstat out to test it. As labman said a wiring schematic would be a great tool to help you figure out the problem.

How long does it take to fire up? What was the temperature range of the gas valve you used. NOTE: gas valves used outdoors in the winter need to be rated for low temperature operation. A regular indoor furnace gas valve will not work.

Low ambient gas valves are needed under most circumstances. The useful temperature range of a gas valve can usually be found in the instruction supplied with the valve. Sometimes it is also marked on the valve.

[Zerox1969]

It had the problem prior to replacing the valve. I replaced with a valve a local fix it shop sold me. It seems to take 5 minutes on occasion, no wait during day, and at night it can sometimes not start for hours or until the sun comes up and hits the AC unit. It only gets to about 35 degrees out here in Arizona.

Any idea what setting I should have the camstat at? How would I "jump out the camstat? Do I just bypass it? Any idea which cabels to jump through?

I read in a post that the flame sensors need to be cleaned yearly. Its pretty dusty out here, could that be the culprit?

There is a schematic, but its faded and I can't make it out.

[hvac1000]

Sorry but I have no wiring diagram for your unit.
Yes you can always clean the flame sensor. For some reason the flame sensor is a weak link in many systems.

You will have to follow the wiring out to see where it goes and then determine what to jump to what for a test. Yes you can bypass the control to test it.

You might look at the sticky notes at the beginning of this board to see what the fan and limit control may look like. (Pictures)

35 degrees is not cold enough to cause a problem with most gas valves. I thought it may have been much colder where you live since you did not post a state or location.