Window switch only works when hooked up to external 12v source

[jogirob]

Hello all,
My saggy old window switch finally gave out, I had a switch from a 79 Chrysler Cordova on standby for just this occasion. 74 and 79 switches have a different order but the color coding is still the same on the wires that lead to the window motors. I used my multimeter to figure out ground and power. The PO wired things so that the window operates even without the key on the acc/on position so there's an always hot wire in there.

So now for the other weird part. I cannot power the windows up or down when I connect the window switch to chassis ground and to the hot lead. Before operating the toggle switches I get your normal 12.55ish Volts from from the hot lead. After I operate the switch, voltage on that hot lead drops to about 9.something Volts. and stays there until I disconnect the hot lead from the switch.

I bypassed the switch entirely by jumping the hot lead directly to the driverside window motor, and the other lead I connected to the chassis ground wire....but nothing happened.

I do get good continuity on the chassis ground wire. I get good 12.4+ V on the hot lead.

I used a 12v battery from my fish finder directly on the window motor and it did roll up and down without a problem despite being a smaller battery that hadn't been charged in months.

I took the power and ground leads from the switch and wired it unto my small 12v battery with the rest of the wires connected to the car as they're supposed to and guess what, the window switch worked flawlessly!

So what's the deali-o?! I'm about to patch some wires and have it extend under my seat where I'll have the small 12v battery hidden but that'd be pretty darn janky!

Thanks in advance. Oh and the battery is plenty strong enough to crank the car up.

-Jo

 

[Big Bad Dad]

Broken, or partially broken wire? Does it change if you move the wires around? I had a problem with the windows in my dodge truck. Turned out these was a break in the wire where the harness moved as the door opened and closed. It was only making connection with the door open...

 

[Brandy]

You have a bad wire somewhere between point A and point B. Your choices are to run a separate wire between the battery / run circuit and the window switch or find the break. I know what I would do....

 

[jogirob]

Ah yes, time for some voltage drop tests.
For starters I'll try to run the switch with my own ground wire hook up and see if that does anything, if not I'll route a wire directly to the car battery and see if that does anything. Will mos def be adding an inline fuse if I'm going down that route for a permanent fix.

 

[jogirob]

*Solved*
I did some poking and prodding and eventually found out that the extra wire coming out of the battery positive went directly to the driver window switch. Once I found out which end belonged to which end I was able to pinpoint the break.

The PO had a patchwork of about 3 different wires in order to work an inline fuse in inside the engine compartment. I did away with that mess and just have one patch in the line for the inline fuse. I'm guessing dirt, grime, and water got in there and deteriorated the quality.