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.
The main grounds are located behind the right and left kick panels. Others who live in the salt belt states have found connectors rotted out behind the left kick panel.
I unfortunately do not have a lot of repair history of just the wiper/washer systems. I did compare the wiring diagrams for the two year model trucks and the wiring for the wiper/washer systems is the same. In theory you could use the donor vehicles GEM to test the wiper washer systems. The actual test procedures are quite involved and range from 12 to 23 steps. A scan tool that can read GEM/CTM codes would be highly recommended.
Sparky. I am having a GEM problem but i can hear the battery relay click on and off, and my windows work, it clicks and they wont, then they are back working. When it works it great, when it doesn’t i loose windows, wipers, and interior lights. I think i have ground to GEM problem, where does the GEM get its ground from?
Hi sparky. I have a 97 f150 4.2 ltr work truck with no bells and whistles with wiper issues. The wipers and the washer doesn’t work at all. I checked the fuses and relays, both were good. I replaced the wiper switch and still nothing. Not sure if its a related issue but the air bag light and check engine is on as well. Reading some of the posts I was wondering if it could possibly be the gem? I have a similar truck I’m using for parts the only difference is its a 98 and has the 5.4 ltr v8. If the gem is the problem would the one from the parts truck be ok to use?
Dash lights and turns signals are not functions of the GEM. The engine would not start with the replacement GEM due to anti theft issues. There could many causes for your problems but I would start with checking fuses and switch functions.