Loose wire on Window Regulator?

98 Mazda 626

When the front passenger window is rolled all the way down, it gets stuck in the down position. When rolled down with the driver side switch it happens every time, when rolled down with the passenger side switch it gets stuck intermittently.

Smacking the door where the regulator is mounted usually fixes the problem the first time, although occasionally I have to smack it more than once. The pins going to the regulator read 0.9 and 11.4 volts during normal UP operation, and 1.9 and 10.3 when trying to roll it up when stuck. So the regulator is dropping less voltage when in the stuck position. At first I was thinking maybe a loose connection to the regulator, but looking at the voltage readings makes me think maybe an internal partial short since the regulator is dropping less voltage when it's stuck.

I bypassed the switch and applied current directly to the regulator and the same occurs, so it's not the switch.

The window can be rolled up and down all day with no problem, as long as it's not rolled all the way down.

I'm not planning on fixing this since I can see someone already replaced the switch in an attempt to fix it, meaning the problem has been there for a few years at least, and because the window basically works other than the all the way down case.

I'm just curious if anyone has run into something like this before and potential explanations?

Since the problem only occurs in the fully down position, it'd be my guess that you're dealing with a burnt motor segment. It's that segment that lines up with the brushes in the fully down position, and neatly explains why smacking on the door cures it. In other partially lowered positions, you're not ending on the burnt segment, so it always works.

A current waveform of the passenger window motor might bear this out. Or I could be way off. :silly:

Sounds interesting. What would you expect to see on the current waveform? Have an example?

I was imagining something like a fuel pump waveform with a dead segment. Steady current draw, with intermittent spikes to zero. I don't have any examples of a window motor with this symptom, 'cause I've never encountered it. :silly: But, I imagine the waveform will be similar.

So I took an amperage waveform rolling the window up:



It goes to about 13 amps at the start, oscillates between 4-6 amps while rolling up, and when it hits the top spikes to 13.4 then quickly levels out at about 12.6 amps.

When I take a waveform when the window is stuck down, it's a constant 12.6 amps, with a slight downward slope.

Maybe when the window is rolled all the way down it's getting physically stuck somehow? Like maybe the top edge of the glass goes slightly under the edge of the frame and when I smack it that frees it up?

Wow, 12 amps when stuck down? :blink: Scratch my failing motor theory.

I think you're on the right track with the binding window or regulator idea. I'd suspect a regulator problem first, just because it moves and flexes more than the window channels.