A heater may be a simple system but poor performance can be hard to diagnose. As the heating season warms up, here are two simple troubleshooting tips to put near the beginning of your diagnostic process:
1. Wireless Ground Connections
A bad ground connection can rob the blower motor of the voltage it needs. If the motor has a black ground wire, your inspection is pretty straightforward. Follow the wire from the motor to its terminus and make sure there’s no rust, paint, dirt, or some other obstruction to impede the connection.
But some motors don’t have a ground wire. Instead, they depend on their mount for a good ground. If the mount’s ground path is somehow interrupted, then the blower motor won’t be grounded, either.
Use a multimeter to make sure you’re getting full voltage to the motor. Once you know the voltage is adequate, you can then look for worn brushes, dirty squirrel-cage fans, damaged fan blades, and other more typical motor problems.
2. Deteriorating Hoses
It’s amazing the amount of debris that can accumulate in coolant over time. Some of these contaminants are big enough to plug water valves and potentially damage the heater core.
What’s the source of this debris?
Much of it comes from hoses, which tend to deteriorate from the inside out and shed material into the coolant. That’s why it’s important to promote coolant changes at recommended intervals—and to replace hoses that feel spongy.
One final note about heater components: always match replacement parts to the original spec.
For example, if the vehicle uses a long-life motor, the replacement should be a long-life motor. Long-life motors are rated from 6,000 to 12,000 hours of service life. Standard motors—with their sleeve bearings and shorter brushes—are rated at 4,000 hours. It may be tempting to use a cheaper part, but the difference in service life helps explain the value of using the right OE-quality replacement.