Melted heater relay

[RedRocket]

So I have a 04 vibe. Alternator started slinging grease so I opted to replace it before it went completely bad. Put a new alternator on, first drive, I turned the ac on, it took a second to come on, came on and blew for about a seconds then went out and wouldn't come on. After a little research I found out where the heater relay was located. Got it out only to realize it was melted/burnt. I checked the voltage at the alternator with the car running and it read 14volts. I then checked the hot wire for the heater relay and it was reading 14.3volts. Is this to much? Is my new alternator over charging?

[andrewclaus]

14.4 Volts is pretty common for alternator output when charging.

The relay burned either from dirty contacts or an overload in the blower motor circuit.

[joatmon]

I agree the voltages sound normal.

The heater relay coil gets power from the 10A gauge fuse, I'd expect it to blow before the relay coil got hot enough to melt the relay, but who knows.

Uncommon, but sometimes some people here have had problems with a relay in the panel above the glove box working itself loose. Of those, the tail relay was more than others, but its a remote possibility that the heater relay was only making minimal contact with the socket, and current through resistance = heat. Or maybe the relay was bad internally somehow.

Doesn't explain why it happened just after the alternator replacement though. could just be:

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