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How to Troubleshoot Rear Hatch Lock Actuator

05-21-2011, 02:37 AM
All my locks work except the rear.

I checked fuse #8 and it is OK (OM says this is fuse for rear lock.)

What is the lock circuit? There is a RED and BLUE wire on the connector:

is the ground involved in the actuation?
what is the actual voltage input?
what is the difference between LOCK and UNLOCK actuator input?
how to bench test the actuator?

Thanks in advance,

PS. This lock has been inoperative for some years. I seem to recall when I first got the van used, I tried to diagnose the voltage input to the actuator and could not make any sense of it using a DMM. I thought that maybe there was some kind of exotic waveform (who knows what FORD might do, eh?) and that I would need to put an oscilloscope on it to see what was going on. Obviously, I abandoned the project since that was too much work at the time. But this is all from memory...

05-28-2011, 08:20 AM
No exotic waveform, just an on/off pulse. It will be a relatively short length, so it might be hard to really see it on a digital multimeter. If you have a peak hold feature on your meter it would catch it. A light bulb across the circuit may be a good substitute here. An analog meter would at least give an obvious meter movement.

My 2003 uses relays out of the rear control module for the rear door and rear hatch locks. In my case I was blowing the fuse whenever I would activate the door locks. The wiring had rubbed against the hatch frame and cut through the insulation. Pull the cover off of the door and check the wiring thoroughly. A bunch of stuff on my 2003 switches the ground rather than the hot. I put both voltmeter leads across the circuit rather than just clipping negative to ground.

Hope that helps.

05-28-2011, 10:39 AM
Hello, 2k3
I recently made my first visit to Daphne and Fairhope. Impressive area. Don't know any good real estate (single family residence, near water) opportunities do you?

(How's this for stealing a thread?)

05-28-2011, 07:27 PM
2k3, thanks.

I put 12v DC across the red and blue wire in the connector and got actuator action in one direction. I refersed the polarity and got the other direction.

So that says the actuator is OK.

I did check the fuse (I believe it is #8 on the interior panel.)

I do have a constant door ajar warning light that is due (I think) to the contactors on the RHS sliding door. I don't know if that warning would deactivate the rear hatch lock.

I think I read somewhere that the rear hatch lock runs off of some "rear module." If thats the case, the problem could be that.

I will have to check the leads to the rear hatch for abrasion. I'm thinking your talking about the flex wires that are along to top edge closer to the RHS hinge?


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