[Flyers1]

Having a problem with my AC/Furnace. AC was working fine and was turned on for about 3 weeks. Thursday night it cooled off and we opened up until Saturday morning. On Saturday morning the AC would not turn on, neither would the furnace side. Furnace is a Janitrol GMP100-4, 14 yrs old.

Checked all breakers and they were OK. Thermostat was calling for heating/cooling. Checked circuit board and 3 amp fuse was blown. Replaced fuse and it popped again. Called local HVAC guy since it was Saturday and hot and he came over and stated that the transformer was shot and replaced it. He also checked and recrimped connections for the thermostat wires. Afterwards, he checked the AC and furnace the furnace appeared to begin starting up, the element would light but NO burner activity. This would just continuous cycle like this. The outside AC unit would not kick on but the inside blower would start.

He thought there was a short somewhere. Told me that problem could be 1 of 2 items, 1) bad thermostat since it was only sending 20V to unit instead of 26V or 2) thermostat wiring short between furnace and outside AC unit since he saw some gnawing in the garage from apparent mice activity. He advised me to check those two items to save some money. I was not real certain that he was on the right track or just confused.

Today, I replaced the thermostat and ran a thermostat cable from the furnace down my hallway and through my garage doors right to the AC unit to test his theory, same issue. I see voltage of about 20 volts at the end of the wires. When I connect the wires, there shows 0 volts at the contactor connections. I also replaced the control board, no change.

I did some measurements:

25 V or so from R to C
25 V or so from Y to C in cool mode
25 V or so from W to C in heat mode

During heat cycle, red light on board stays on solid, unit attempts to start, igniter glows but no burner action. This happens 3 times then unit goes quiet. Gas valves and control appears ON.

During cool cycle, exterior unit does not kick on.

Could he have wired the transformer wrong to cause both of these problem? If so, how do I correct without bringing him back?

Any suggestions?