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I’m upgrading my window motors as I finish the restoration of my pre-L car.  With the initial (native) motors in place the fuses blew every time I’d pull the switch.  I figured it was the old motor, old grease, poor alignment, etc.  I have purchased Taurus motors, modified the regulators, run them on 12v source w/good movement, and installed the setup.  Everything runs/moves as it should under direct 12v power w/o binding.  However, yet again, when I connect the new motor to the harness, pulling the switch again blows the fuse (25 amp) immediately.  What am I missing?

Last edited by George P
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The key here may be “restoration”. Do you have any prior operating hours with this vehicle?

that is, have the factory window motors ever been proven functional during your ownership?

there are two motors and two switches, one for each window. Do you have the same problems for both switches/windows?

what you are describing sounds like a short in the wiring and/or the window switches. but a short in each window’s wiring harness and/or bad switches for each window seems highly unlikely.

summary of questions-

have either of the windows ever operated during your ownership?

do you have the problem with one or both windows?

during your restoration have you connected wires to bare switches or are they still wired as they were at the time of purchase?

long-distance troubleshooting is difficult. Giving us some more details will definitely help.


As Larry says, it's hard to troubleshoot from afar. It seems that if the fuse blows when hitting the switch that there is a short. I've seen that with headlight motor switches that were bad and caused the fuse to blow right away. I would unplug the wires from the switches and check for shorts. Use a voltmeter that has a continuity tester to test. If there are no shorts in the wires, then plug one switch  in at a time and check again. Bad grounds can cause all sorts of problems also.


Thanks for the replies.  To answer some of the above questions.  I have very little time driving the car (corner of my street at drop off two years ago (pre-COVID) to my house …that’s it.  At that point I began dissecting it fully.  Can’t remember which of the two windows actually worked.  Both original motors turn when connected directly to 12v power.  I have the wiring COMPLETELY pulled apart with the dash and heater box out of the way.  When the motors (again, newly installed Taurus versions) are connected directly they run w/o a problem.  The switches have been replaced with brand new ones because I thought too that it could be an issue internal to the old switches …still happens.  I’m not sure if there’s an issue with the other window (driver side) as I’ve not hooked that one up yet.  I suppose I should/could do that first to see if it also blows a fuse …that would likely be a simple 1st step.  

If you can get one switch and window motor to correctly function that will be a help for your troubleshooting.

that will confirm you have one correctly wired switch and one operating motor.

(getting the wires correctly connected on those window switches is still a problem for me after 20 years)

you can then use the good switch to control the bad motor and see what happens

you can use the unproven switch with the good motor to confirm if you have two good switches

if your 12 V testing is just with a motor sitting on a bench, that is a different world than with the motor connected to the gear drive and raising the window

thanks for the additional information.

if you haven’t already you should study the wiring diagrams at




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My embarrassment is overshadowed only by my raw excitement that this was a quick and easy fix.  I did indeed have the wiring reversed on the new switches (which only perpetuated the problem w/the older switches I replaced because I wired the new ones like for like and only copied the problem).  Thanks again for the help.

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