AC and Heat won't turn on. 4 Light blinking on furnace.

[Luey]

Hi guys,

First time posting since I got a problem on my AC or Heating unit. My AC/Heating was working fine until I came back from short vacation. My furnace is a Coleman model #DGAA090BDTA and a Trane AC unit.

I set my thermostat for heat or cold and my unit would not turn on. Check fused and all is fine. Check my furnace and light indicator is 4 blinking pointing to limit switch being open. My unit is a downward blower. I'd only saw one limit switch not sure if it's upper or lower. Writing on it is 025-35381 L145-30F.

My question is this the only problem? If I replaced this part will it fix my issue or do I need further testing? If so what do I need to do? Any help is greatly appreciated.

Thank you....Luey

[Luey]

Okay...I've found the upper limit switch. Tested the lower limit switch and I got low resistance reading on my multimeter.

The upper limit switch with no number written on it has no reading whatsoever. No continuity or high resistance. Could this be my problem? The upper limit switch?

Luey

[Luey]

Nevermind...I've found the culprit. It was the upper limit switch.

By jumping I was able to turn my AC on.

[Robert]

I replied to your email.


Thanks,
Robert