1991 XJ power door lock issue

[Bobburt]

Doors all lock like you would expect of them; fast, normal.
Front passenger door unlocks slow, the rest including rear hatch do not unlock. Doesn't matter which switch I press. Doesn't matter if the Jeep is running or not.

I've been testing all that I can think of. Tried new relays, no change. 12.5v to domes/vanity/courtesy/glove box lights/RKE, 12.5v from the fuse block to the light green wire at both relays. Windows roll up and down fine, so it's probably not the 30amp circuit breaker.

For some reason, there's a huge voltage drop in the unlock relay/circuit. The relay gets 12.5v in, and puts 5v out when I hit the switch, not nearly enough to power a lock actuator. The voltage drop eventually goes down to 0.6v at the rear hatch actuator.

I've tested the entire circuit for resistance. It's around 85-90ohms, which from what I've read around is considered normal? I'm still not entirely sure.

I checked all the door hinge boots and there aren't any broken wires as far as I can tell.

I haven't changed anything related to any electrical stuff. This just happened out of nowhere. I noticed this happened after I replaced the headliner so I'm wondering if I bumped or broke something along the line.

I don't know what else I can test. Any input would be greatly appreciated.

Here's the wiring diagram.

 

[dan1977p]

Pull the door panels and grease all the joints in there. They probably haven't been touched in 25 years

 

[trippled]

When you're running the locks, do you still have 12v into the relay? 5v is no good.

 

[Bobburt]

I've been doubting it's the joints in them, they lock just fine; like you would expect a door to lock. But I'm gonna grease them regardless.

When I lock them with either switch, or when the switches aren't being touched, they get 12.5v in.

It's only when I hit unlock on either switch does the power drop, both in and out, to 5v.

 

[Bobburt]

Ok, a little update.

I've since greased all the mechanisms. No change.

I've changed the circuit breaker just cause. No change.

I pulled the front carpet out so I could check the wires running from driver to passenger. All wires were intact and in really good condition considering the age of the vehicle. No pinched or cut wires at all.

And I was mistaken earlier. When hitting unlock, the voltage to the fuse box does drop. I tested it on the dome light fuse and it actually drops to 7 volts there, and to 5 volts at the unlock relay.

So I've got awhile before I put my carpet back in to take care of a couple leaky and rusty spots, and gotta wait a few days for the foam under the carpet to dry. Does anyone have any suggestions of what else I should check or try?

 

[dan1977p]

Your linkages could also be bent causing friction but if you're saying you're only getting 5V to the relay and expecting 12, I would hot wire the locking mechanism directly inside the door to see if that help. If it does, may be bad grounds before the relay. What is the output on the relay? If you're checking the signal wire, I would expect lower voltage there but still 12 going out but I don't know for sure.

 

[Bobburt]

When you say output on the relay, I'm assuming the wire that goes to all the door actuators? For the unlock relay, it's pink/violet and it only outputs 5 volts when the switch is hit.

On the lock relay though, there's not really any unsurprising power drop. The voltage to the relay drops to about 11.5 and the output voltage is 11.5 when the lock position is hit.

 

[dan1977p]

I mean the wire going from the relay to the door lock actuator, not the wire going from the switch to the relay. Since you're getting 11.5 volts out of the relay, I would suspect its a mechanical problem or the actuator is bad. Check out this part of the FSM for door locks.

Door Locks Troubleshooting

 

[Bobburt]

Even with the slight voltage drop, the doors lock normally.

But that FSM section helped me finally understand how the lock/unlock wires are routed to the doors, and why the rear hatch actuator is only getting 0.6v when either switch is in the unlock position.

I'll give those tests on there a try.

 

[Bobburt]

"(8) Hold driver’s side switch in UNLOCK position.
Measure voltage at unlock relay terminal 1 (86).
Meter should read battery voltage. If OK, next step.
If not, repair open to driver’s side switch."

This is where the voltage drops to 5.

I don't really understand how open circuits work. If there is an open circuit somewhere, how would I go about finding it?

Or is it possible for a ground to be "open"?

 

[Bobburt]

I couldn't figure out where or how an open circuit might occur.

So, as a last ditch effort, I decided to drop the headliner to see if the issue goes away, like to how before I put the new headliner in. And sure enough, as soon as I dropped the front half of the headliner, the doors lock and unlock like they should straight from the factory. Somewhere in the ceiling is a pinched or exposed wire or something, touching bare metal, or something.

Shouldn't be too much trouble now. Thanks for all the replies and tips.

 

[dan1977p]

Glad you found the smoking gun.

 

[Bobburt]

The junction or bundle of wires at the top of the passenger window is where the problem was. There's a little notch in the sheet metal and the wires were routed and squished through it, and would get pinched when the headliner was pushing up against it.

Took most of the tape off to see if there were any exposed wires just to make sure. Ended up re-taping that bundle and the wires going to the vanity lights in the mirrors. Headliner's back up and no more pinched wires. Locks are working like they should now.