All power windows slow or no go. problem found.

[KentuckyBuck]

I have recently identified why my 1987 Grand Wagoneer's windows were slow or not operating.

I have been having trouble with all of the windows not having enough power to go operate. I thought at first that all the actuators were old and tired but when I hot wired my front driver's side window, it worked fine. I checked voltage when I operated the window using its normal wiring harness and I saw a 3 volt drop. I decided to dive into the electrical distribution system and try to isolate the fault.

The following 3 diagrams were most useful in tracing the circuit:

http://oljeep.com/gw/elec/88/88_FSJ_Wir ... mPage1.jpg
http://oljeep.com/gw/elec/88/88_FSJ_Wir ... mPage3.jpg
http://oljeep.com/gw/elec/88/88_FSJ_Wir ... mPage6.jpg

I was able to get from the battery to the bulkhead wiring connector (position D4) without voltage drop. I bought a little "add a circuit" device and plugged it into the fuse box where the 30 amp breaker for the windows is and I was able to see the same 3V drop when I operated the windows. This indicated that the fault was between the battery side of the fuse box and the D4 position of the bulkhead connector. Aside from a couple of feet of wiring, the only thing between the fuse box and the D4 position is the ignition switch. I picked up a new ignition switch from my local NAPA for $15.

On my FSJ, the ignition switch is mounted on top of the steering column. I had to take a few pieces of trim off below the steering column, unbolt the bottom flange where the column goes through the firewall and then I had to unbolt a bracket that holds the column up against the dashboard. This allowed the column to be lowered out of the way and gave me easier access to the ignition switch. No problem taking the old ignition switch out after that. I confirmed that I was seeing high resistance across the B-3 and A terminals when the switch was in the ON position. I only saw .6 ohm across the same terminals on the new switch.

Installation of the new switch went fine in the reverse order. All my windows worked pretty well after the replacement. They would all benefit from some fresh lube but I might save that for later....

In retrospect, one thing that I found interesting about the pre-fix fault was when I put my key in the ignition with the door open (but before I turn the key to ON), the chime module would sound loudly but when I turned the key to ON, the chime module would sound at a lower volume...maybe 40% less. After I had the new switch installed, this volume drop didn't occur. I cracked open the old ignition switch (springs and contacts fly everywhere) and was able to see carbon build up on the internal parts...specifically the contacts for the ON position and also on the Voltage In contacts. Smoking gun.

[Mexdsk]

Nice write up! Thanks for the info, I am sure it will help others.

[FSJ Guy]

INTERESTING!!! Wow.

Great detective work!

[babywag]

Good troubleshooting!
Not surprising that a ~29yr old switch is in need of replacement.
The late models have pretty good wiring overall, some issues with certain circuits, but like you showed easily found/repaired w/ a little effort.

Just out of curiosity did you notice the voltmeter gauge now showing a more accurate voltage reading?
I've found that on the late models if the voltmeter gauge is reading lower than battery voltage, there is usually a drop somewhere like you found.

[KentuckyBuck]

Tony, I honestly didn't pay any attention to the voltmeter (the dash mounted one) before I started. Since you asked the question, I wish I had. It would be an interesting piece of data. I took a look at the schematics and found that the voltmeter is part of the instrument cluster and is connected to the circuit off of the "ignition fuse". The information it provides is specific to that circuit meaning it would directly reflect the voltage in the instrument cluster but would indicate voltage drops along the path from the battery -> starter relay -> bulkhead connector -> ignition switch -> ignition fuse -> cluster. The path for the power windows follows that same route but diverges at the ignition switch. I would expect that the voltmeter now reads a higher voltage level but had the drop occurred in the wiring harness between the fuse box and the door, the voltmeter would not show an increase after the harness was repaired.

I will look to see what the voltmeter reads now and see how it compares to the levels near the ignition switch. I can't test the ignition switch now that I have put the steering column back together but I can test at the bulkhead connector with little effort.

[GaJeep94YJ]

I finally replaced my switch after the engine would stay running after I removed the key....

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