heater switch
Thread Starter
Drifting
Joined: Jul 2004
Posts: 1,554
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From: Wi
heater switch
I did a search on heater switches. This is on my 64, no a/c. From what i understand, low and medium speeds use the resistor, high speed goes straight through the resistor? I have all new wiring, fuse block, and new blower motor, but the fuse blows on high speed. I have the original resistor yet. In my service manual, it says the heater is fused with a 10amp fuse, and fuse block also says 10 amp for the heater. Possible I have a short in the new blower motor, or is a 10 amp fuse too small? Not that I use the heater much, but obviously there's a problem somewhere that should be resolved.
Tech Contributor
Joined: May 2005
Posts: 15,576
Likes: 118
From: Conroe Texas
Typically in case the heater blower is wired such that the resistor is only part of the circuit for low and medium speeds. In fact, that's why it's there - to step down the current going to the fan on low/medium as a means of getting the fan to operate at a low or medium speed.
So when your heater is on high, the resistor is not used. If you are blowing a 10 amp fuse, then certainly more than 10 amps are going through that circuit, and this is not good.
Have you tried removing the fuse and measuring the Amperage at the fuse location, when the heater is on High, in order to see what kind of draw is there? I would think (but I'm no electrical expert) that if you are seeing 10.5, or 11 Amps at that fuse location, then you are probably seeing a variance due to the new fan. But if you are seeing a significantly higher Amperage level then you've probably got a short somewhere.
IF you measure the Amperage at the fuse location, be sure to measure as quickly as possible. If you do have a short somewhere you don't want to jeopardize the integrity of the wiring by replacing a fuse with a multi-meter, for very long.
Jeff
So when your heater is on high, the resistor is not used. If you are blowing a 10 amp fuse, then certainly more than 10 amps are going through that circuit, and this is not good.
Have you tried removing the fuse and measuring the Amperage at the fuse location, when the heater is on High, in order to see what kind of draw is there? I would think (but I'm no electrical expert) that if you are seeing 10.5, or 11 Amps at that fuse location, then you are probably seeing a variance due to the new fan. But if you are seeing a significantly higher Amperage level then you've probably got a short somewhere.
IF you measure the Amperage at the fuse location, be sure to measure as quickly as possible. If you do have a short somewhere you don't want to jeopardize the integrity of the wiring by replacing a fuse with a multi-meter, for very long.
Jeff
