Have a CT3600A4444 Stat. When I went to turn on heat it blew the 24v fuse. Fuse stay ok when stat is not plugged in housing, blows when stat is put back in housing.

You have a short somewhere, triplecheck your work. may have a crossed up wiring.

you have 24 volt across both terminals of contactor coil? if not and condenser is still running then you have a stuck contactor. also this is a heat pump so you have 24v and common going to out side unit and rodents or dogs may have chewed up wire and causing a short making connection and this would have blew transformer. FYI installing a 3 amp car fuse(spade type) installed in line of 24v coming off transformer will protect transformer as well as other components. your T-Stat may be defective as well.

Two wires to the T-stat should go to W and C which is W for heat call and C represents common!
When the T-stat is set to heat it will connect the 24v red wire to the W terminal therfore sending 24v to the heater and the common wire completes that circuit. Make sure to use an inline fused wire to test so you do not blow your transformer. Easier to replace a fuse then a T-form

Red wire to R on thermostat red on furnace and red on heat pump Same with white except w1 on thermostat. Blue to common on thermostat common of furnace (probably brown but will be marked) and blue to common on heat pump. yellow to Y on thermostat and straight to heat pump. Orange to O on thermostat and straight to heat pump. If wired correctly with no shorts fuse problem should be solved. commonly people leave enough wire exposed inside the t-stat for wires to short together. This will blow the fuse. Hope this helps. I understand the frustration.

The exhaust is clogged or restricted holding too much heat in the exhaust housing or the limit t-stat has gone bad. This is the t-stat sitting next to the thermal fuse. Good luck.

Sounds like you had a direct short on the 24v side
of the transformer. Usually there is a inline fuse that
will blow so it protects the transformer..

Turn power off to unit
-Take doors off unit
-Look for a little fuse that may be located on the
control board where the thermostat wires go.

-Check the fuse, if it is blown then replace. However
you need to check the thermostat and the wires
that go to it to make sure they are not touching.

-If the fuse is not blown, then at the thermostat put
the fan to the on position. Go to the unit and turn the
power on, if the fans starts then things are at least
looking better. If the fan doesnt start, check to see
if the 110/220 fuse or breaker that you have isnt tripped

Hi,
First, Is there batteries in the t-stat that have gone bad? If you are not sure, pull the face off of the t-stat and check.
If that is not the case then it may be a transformer in the furnace or if you are lucky, a fuse in the control board that blew.
If you have an electrical meter, check for 24v AC at R and C on the control board. If there is no power then the fuse is blown or the transformer is gone.
If there is a fuse then check and change that, they can be blown without it looking like they are.
Did a t-stat wire break or come of??? If the R wire braks or comes off it will totally shut things down...

Heatman101

first look for red button neer the copper line set if has one push it second inspect thermostat wires for weed eater damage check disconnect for fuses check breaker at main panel pull disconect and remove cover check stat wire connections look at the capacitor if swelled up on top bad if all look ok put disconect in using insulated object manually push in contactor if unit comes on check for 24 volt ac on yellow stat wire to common if none stat wire could be loose at indoor unit or stat bad hope this helps you

double check your wiring. R terminal on the furnace will provide 24 volts to the t-stat. W terminal in the t-stat will send 24 volts back to the furnace W terminal to turn on the heat. G terminal in the t-stat will send power to the G terminal in the furnace when the t-stat is switched to fan on. Y terminal in the t-stat will send power to the Y terminal in the furnace which in turn will send 24 volts to the A/C outside. The C terminal in the furnace should be connected to the c terminal in the A/C outside as well as to the T-stat. Check the fuse again

you have a short in the wireing.disconnect at air handler and hook-up short t-stat wire to t-stat,ifok chk wire to condenser