Dr. Robert Trane’s book, “Trane Furnaces: Diagnosis, Repair, and Operation” is a classic in the world of Trane furnace repair. The Trane Furnace Code TP5 article is a great way to brush up on the Trane furnace repair code and learn what Trane furnace code TP5 is its causes, and potential fixes.

What is Trane Furnace Code TP5?

Trane Furnace Code TP5 is the code indicating that the furnace’s blower motor is failing. If a furnace’s blower motor fails, the furnace can’t cool the house. The blower motor provides the air conditioning for the furnace and the air is blown through the coils to heat up the air for the house. If that part of the furnace stops working, the furnace isn’t going to be able to do its job. Trane furnaces have a blower motor with a built-in relay to automatically switch over to the blower motor when the furnace’s burner shuts off. If that relay stops working, the furnace is going to lose heat and never be able to cool the house.

What causes Trane Furnace Code TP5?

The most common cause of the blower relay failure is the removal of the relay when installing a new blower motor. With the old relay out of the way, the furnace’s relay can’t make that electrical connection and the furnace stops working until the relay is replaced. Another common cause of the relay failure is corrosion in the relay contacts. A buildup of mineral deposits around the contacts can cause intermittent contact, which is another way of saying the relay is constantly trying but isn’t making good contact. That’s usually a result of either too much heat or a buildup of condensation between the contacts. Either way, it means that the furnace isn’t getting the air conditioning it needs and the house is too hot.

Fixing Trane Furnace Code TP5

The fix for Trane furnace code TP5 is to replace the relay with a new furnace relay. The relay will make good contact so the furnace can start working again. Once the furnace has cooled down a bit, though, it’s a good idea to have a technician replace the furnace blower motor. The blower motor works with the relay to ensure that air conditioning is provided to the house. If the relay fails but the blower motor doesn’t, the furnace won’t be able to perform its job.


If you’re noticing that your Trane furnace isn’t providing enough air conditioning, or it’s getting hot in your house, you might want to check the compressor running code. The blower relay is the most likely culprit. The relay controls the compressor and if it stops working, the furnace won’t be able to keep the house cool. In either case, replacing the relay will put the furnace back in action and provide the air conditioning that your house needs.