Chevy & GMC Vans

Hey guys. It's been a while!

I'm volunteering to route mark for the ride to conquer cancer again this year, and I decided the occasion was a good excuse to do some van maintenance. One thing that's really been bugging me is the power door locks. 3 out of 4 of them don't fully function. They try, but they're unable to generate enough force to toggle the locks, even if I apply 12V directly to the motor with a good battery. I took one apart, and the brushes and commutator are in good shape. I tried cleaning and lubing it, but it was still weak . I can't figure out why this motor is just giving up. Any ideas?

I do not know what year you have but on most years all the locks are wired in parallel meaning one of the locks could be causing your circuit to draw too much amps.

The locks are like the windows, they will stop working from too much heat from amp draw. Then if you wait a while they will start to work again. It seems that there is a thermal switch that wears out like the windows but is not easy to replace or fix. Sometimes you only get a couple of button pushes before this happens.

One way to find it is to disconnect each lock one at a time to find the problem or connect only one lock at a time to find the problem lock. I just replaced my passenger lock actuator which allowed my three presses. It finally stopped working so I replaced it. Now I get close to ten presses in a row before all power starts to fade.

If you have a liftgate the same problem can be caused by that lock also: viewtopic.php?f=10&t=9031

I think you're onto something. I noticed that if you leave power applied to the actuator, the current decreases gradually. I also noticed a rectangular sandwich of metal inside (see pic). If I apply power to the connector terminals, the actuator is weak, but if I apply it directly to the brass tabs, bypassing the sandwich, then it is much stronger. It must be some kind of current limiter or thermal protection. As you say, it must be faulty. I wonder what would happen if I put a jumper across it?... would the motor burn out even though the circuit is fused under the dash?

Sure enough, the resistance across this "fuse" was about 80 ohms. This was the case with the other two locks as well. Either oxidation builds up on them, or as the motors stiffen over time the heat destroys them. Anyway, since these actuators are pooched and not serviceable, I decided I might as well run 'em into the ground. I soldered a bridge across the fuse, and they're back to moving vigorously. I'll just have to be careful not to hold the switches down too long.

Awesome, Glad you got er figured out !
And hey, Where ya been ?!?!
Nice to see ya round again.
Carefull you dont have anything bumped up against one of those switches too.

Hey- I ended up doing very similar to you, without finding this thread first.

Could I suggest changing the thread title to 'fix for weak power locks' or something like that, perhaps with the part number (assuming this was the stock Valeo 5045877 actuator)?

I also found high resistance across the rivet coupling between the bus bar and the brush holder. Soldered that as well.

If you care to harvest more pictures, there are some here
https://photos.app.goo.gl/CcpyM5mKJhEUAPE3A