1969 blower motor keeps blowing fuse
#1
The fuse blows everytime i turn on blower switch. I jumped the fuse this time with a wire and noticed the blower has one speed. Also I used my volt meter and unplugged the plug that connects to the resistor and checked for voltage. I noted medium setting would have voltage reading on two pings as well as high setting. What should the voltage readings be on the plug that connects to heater box resistors?
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#2
1) Use a headlamp globe rather than wire as a fuse replacement.
2) Pull the wires off the motor and see if the globe gets bright (should not come on at all) - That will isolate wiring faults from motor faults.
3) Sorry don't know about resistance values. Would not be supprised by values in the 0.25ohm range.
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#3
Its not a short. This is what I have. Switch that looks like it is for AC car but my car is non AC and heater box is non AC (green lead goes nowhere on plug). Resistor I think is the issue although it passes for continuity. I cannot find a non AC replacement but the ones made for AC cars look identical. Can I use a heater box resistor for AC cars for non AC heater box? need to know the difference.
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#4
I would think the resistors are the same as I would suspect that the blower motors are the same, just in a different box. Did the car have a/c that has been removed or dash parts for a/c that was never there?
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#5
As per marti report it came with heater only. I assume the heater switch was replaced by previous owner with the one that has ac green wire but there is no ac in car or in dash. I bought the resistor for heater box with ac so I will know soon enough. What puzzles me is why I have two 12 volt leads when in medium and high speed. Seems switch was designed that way. I bought another switch made for heater only and there was no difference in design. Anyone have more info? Hopefully this is not the reason for blown fuses
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#6
As I understand it the switch applies either full 12v across the motor (full speed) or through 1 or more resistors (even if the resistors are in the same block/part) to give slower speeds. I would guess that the resistor block you bought has 3 terminals; Common; Resistance 1; Resistance 2. To get full speed the resistor is by-passed. Slowest speed - highest resistance. What is left will be the connections for medium speed. Any help?
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#7
thanks, i installed the new resistor but only high speed works and motor makes noise. At this point I assume its the motor. I thought it was the resistor but now i know its not. I tested the blower motor at first by connecting it to battery and it was working but it never really spinned smoothly when i turned it by hand. I'm not sure how much it should spin freely if i give it a good twist. The only thing i can assume now is that the low / medium speeds is not enough current to spin it. BTW - in medium speed the resistor started to glow red hot.

I know its not the switch as i checked for continuity on each pin. If you happen to have one, can you tell me which pins have continuity with each other? This was my results

low = low pin and supply pin
medium = low pin, medium pin, and supply pin
high = high pin, medium pin, supply pin
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#8
That sounds about right. The current will take the path of least resistance (bit like me at work). The facts 1) motor is not smooth turning and 2) glows up the resistor at slower speeds points to motor problems.
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#9
Problem fixed. I replaced the motor with a new one. Wish I had done this in the beginning instead of doing the job twice.
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