We have come across some jobs in the past where the furnace 3 amp fuse blows when the AC or Heat Pump is activated. Diagnosis is below.

Diagnosis:

1. Replace Fuse
2. Restart call or heat pump or Air Conditioner
3. Does unit fuse pop soon after the unit starts? Or immediately?

• Immediately- Verify contactor and wiring. Shorted Contactor is usually the culprit.
• Soon after -  This is typically due to one of the high or low pressure switches in the condenser. Use jumpers to jump past the switches, test operation.

For replacement:

Typically these are brazed in to the units refrigeration circuit. It is easiest to get a tee for your service valve and a new pressure switch of the same rating.