This 1997 Ford F150 came in with three complaints. The power windows do not work. The wipers do not work and the interior lights do not work. Figuring that they were all related I decided to test the easiest system to access, the power windows. I pulled the driver’s side power window switch assembly up and checked for power at the light blue/black wire with the key on. No power.
I then went to the interior fuse box and removed the battery saver relay. It is the small relay second from the top left corner.
I checked for ignition power on the lower right terminal, 12 volts, good.
I checked for ground at the upper right hand terminal by first placing one lead of my voltmeter to a positive battery source, 0 volts, bad. That in itself is enough to show that the GEM module is faulty but I also looked at GEM data with a scan tool and saw that internal system voltage was 22 volts. Hard to do with a 12 volt battery. Diagnosis of a faulty GEM module. To see how to replace the module please click here.
This is the reading with a new GEM module across terminals 85 and 86. Just like it should be 12 volts. Another important note is that I asked the customer about water leaks on this side of the truck and also closely inspected everything as I disassembled looking for signs of water intrusion. Water leaks are a big problem with these modules.
Again with the new GEM installed there is now power on the light blue/black wire.
In case you have not already figured it out if the windows had to be operated to raise a downed window you could do one of two things if there is no power at the light blue/black wire. One, you could apply 12 volts to this wire with a jumper wire. Two, you could jumper terminals 87 and 30 together at the battery saver relay. The second will also test the wiring in the door jamb as well.
Since you have a measurable low voltage at the power outlet, you need to determine if it is being caused by the ground or power circuit dropping out.
Hi Sparky, my name is Sergei. I have read all your answers here and another post – amazed with your knowledge. Still need help. 99 Expedition while driving suddenly driver’s window goes down by itself, can’t roll it up, other windows don’t respond as well, door locks try to work, but weak, blower dies, radio sometimes too, buzz in a fuse box when try to operate doors or open windows, portable voltmeter plugged in power outlet shows 6v. Car drives perfect. All symptoms at the same time. Sometimes fixed all by slamming the door hard, disconnecting ground (I put switch inside). I removed GEM and look at it now: pristine, no signs of water or any loose solder, no dust. At the fuse box harness connectors couple of lower contacts have water signs. Will clean. Should I replace GEM?
Thank you so much,
Sergei
My recommendation would be to do the testing outlined in this article once the power windows have stopped working.
Sparky,
No problems with the wipers or anything else. Everything works including the driver window switch until the 4×4 high then low light comes on, then a click and after that no driver side window.
Very likely that it has. Do you have a problem with the wipers and dome light as well?