The heater fan quits working on colder days. It is not the fan motor, as twice after it has quit, several days later the fan began working again. As controls are switched, the indicators light and mode shifting sounds can be heard. It seems to be that the fan quits on the colder days (<38 deg) the will resume woking again when the outside temperature exceeds 50 degrees.
So, (sorry VDCdriver, couldn’t resist) why do you say that it is not the fan motor?
It is not uncommon for the blower motor brushes to wear out such that the blower can stop on a dead spot and then won’t restart until car movement causes the rotor to turn to where it is not at a dead spot. The last blower motor that I replaced had exactly this symptom, it would run for a while and not run for a while.
It could be wiring, it could be the blower speed controller, or it could be the climate control head unit, but it is most likely to be the blower motor itself.
To see if the motor may be at fault like Tardis said check the voltage across the leads to the motor with the speed control set to high. If there is 12 volts on the leads and the motor isn’t running then the motor is the trouble. If there isn’t 12 volts there then the trouble is elsewhere. Possibly the blower relay or a bad power connection.
Thank you, I will check the motor. I just thought there might be a loose cable connector that has oxidized contacts or something that the change in temperature would affect. Also possibly some outside air temp sensors somewhere that I may be able to bypass.
I hope the motor is accessible without disassembling too much housing or whatever, so I can check the motor voltage.
I will check the motor. Also I will try to find the cable harness connectors and spray them w/ electrical contact cleaner.
The car is not garaged,it resides in Alexandria, Va. where we had an ice storm last night. This am I had no heater or defroster. Interesting if when the weather warms back up the blower starts running again, as it has five times this winter quit until the weather warmed back up.
The motor could be the problem but I think the relay is a better suspect from what you say about the trouble. If you find the relay tapping on it lightly with a screwdriver handle may reveal the problem.
There is a high (maximum) speed relay, but lower speeds are controlled by a power transistor. Relay failure would make the maximum speed slower, but it wouldn’t stop the blower from running. The relay is inside the speed controller with the transistor. It’s mounted mostly inside the blower box, to the right of the blower motor.
The last time I had an intermittent blower it was just a bad connection. The connector had gotten corroded from some moisture leaking in due to clogged up cowl drains under the windshield. So I just cleaned up all the contacts and that was the end of that. The only way to know is to pull the connector and look at it.
If the connectors are clean and tight then the next time the fan isn’t running despite being set to run, give it a sharp whack with something like a rubber mallet. That overcomes the issue tardis mentioned. If a good whack gets it going then you probably do need a new motor.
If that doesn’t bring any results then its time to break out the voltmeter and start tracing the circuit.