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99 Astro power lock

Old  March 1st, 2012, 5:44 PM
99 Astro power lock

Hi all,

Have a 99 Astro van with a strange problem. The power lock switch on the drive side does not work when pressed. I can use the passenger side power lock, the lock on the remote and both function as expected. I figured it must be the switch and spend $20 with RockAuto and replaced the switch, but still same situtation and not working. I guess now I need all of you to help me understand and diagnos/determine what's wrong. Thanks in advance.

Last edited by courtroom74; March 1st, 2012 at 5:50 PM.
Old  March 1st, 2012, 10:33 PM
  • CF Veteran
    Join Date: Mar 2011
    Posts: 1,706
Welcome to the forum. I've seen defective switches out of the box. Take the switch out and then make sure you have good voltage on both orange wires that supply power to the switch. Then, measure the resistance between terminals F and H and also B and D on the switch while working the switch. The switch passes the voltage to the white wire (terminal H) in the unlock position and the light blue wire (terminal D) in the lock position. If they all check out, you have a wiring problem downstream.

Old  March 2nd, 2012, 5:12 PM
Great, thank you for the pointers. Will try it out over the weekend and see if I can make head/tail out of it. Thanks again.

Old  March 3rd, 2012, 5:27 PM
Just finsihed testing the switch (attached to the wire harness) there's no indication of resistance, nor votage when I active/press the switch (on or off). Or should I be measuring the terminals for resistance by itself without the wire harness? Any comments/suggestions are welcome.

Old  March 3rd, 2012, 5:45 PM
  • CF Veteran
    Join Date: Mar 2011
    Posts: 1,706
I was assuming the switch was isolated from the wiring. Measure the resistance (actually continuity, i.e., resistance approaching 0 Ω) between the terminals on the switch. Terminals F and H on the switch should be internally connected for unlocking and B and D, for locking.

Old  March 3rd, 2012, 7:40 PM
  • CF Junior Member
    Join Date: Jul 2008
    Posts: 46
I found broken wires at the umbilical between the door and the frame. Although, it wasn't lock that were affected. But since then, my drivers lock has stopped like yours. I haven't had a chance to look, but I suspect more broken wires.

Old  March 4th, 2012, 12:17 PM
Hi all,

This is what I just tried. I discounted the new switch from the wire harness. I used a digital ohm meter meter, first touched the two leads together and the meter changed from 0.0L to -0.000 (closed circuit, I think?). When the leads are apart, it reads 0.0L.
Then I placed the leads with terminal F and H (orange, white) which does not have any movement and still reads 0.0L (open?). Did the same with B and D (orange, light blue) and same result, no movement 0.0L.

I went back to the old switch I removed and tested the same way with identical results. Does that means both old and new switch are defective?

Old  March 4th, 2012, 12:46 PM
  • CF Veteran
    Join Date: Mar 2011
    Posts: 1,706
Were you working the switch? Both circuits are open at rest. Then, terminals F and H on the switch should be internally connected (circuit closed) when you press the switch for unlocking and B and D, for locking.

Old  March 4th, 2012, 3:21 PM
Hi EinST,

Was not working the switch before so I went back to remeasure per suggestion. Both switches (old & new) received the same result where when measure across F&H, B&D when switch was pressed (one way, close or open), I get movement on the digital meter (something like -.003) and it's no long at 0.0L. I supposed this is an indicator the problem is else where and not at the switch since both acts the same.

If so, what would be the next logical component to check? Is there any relay or fuse that goes directly to the switch? I'm assuming ... since the passenger side switch when pressed, lock work on both side. Or maybe check the power wire ... something simple that I can take measurement and do diagnostic?

Not sure if I can handle dealing with that bunch of warpped up wires without any step-by-step help ...

Old  March 4th, 2012, 5:01 PM
  • CF Beginner
    Join Date: Sep 2009
    Posts: 26
Step by step on the broken wires...
Find a broken wire, repair it
Find another broken wire, repair it
So on, and so forth.

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