98 Windstar Power Locks Going Crazy

This morning I put the key in the driver's door and turned it to unlock the door. All four door power locks actuators kept cycling the unlock function about once per second. I could not get it to stop, so I disconnected the battery for a few minutes. I hooked the battery back up and drove to work. Once I arrived there, I left the van running and had to get something out of the back. When I opened the liftgate, the actuator for the gate started cycling the unlock function. I parked the van and shut it off, and the actuator stopped. Eight hours later, I drove home from work. Once I got home, just to see what would happen, I hit the lock button on the driver's door. When I did, the actuator on the passenger front door started cycling the unlock function. I shut the van off, but it kept cycling until I disconnected the battery. What in the world is going on???? Thank you for any suggestions that you may have.

I can't say for certain, but I've notice strange behavior coming from the GEM (Generic Electronics Module). This module is located under the dash to right right of the drivers legs. It controls most of the interior electrical functions. For example, the GEM is what controls the time delay to turn off the interior lights. It also controls the power door locks and power windows, which is the problem that I experienced.

The GEM would disable the power windows at random times. Initially I thought it was a grounding problem, but I was never able to cure my problem with improvements to the grounding. Although the GEM isn't meant for disassembly, I managed to remove the board from the plastic enclosure without breaking it. I found that one particular pin on one IC package was the location of the fault. When I would touch it with my meter probe, the GEM would work OK, usually for several days, but the problem eventually reoccured. I reflowed the solder joints to this IC to fix the problem.

You might be able to fix this by replacing or repairing the GEM. In that it is the master control for the door locks it is a good place to start looking. I believe diagnostic codes are stored for the GEM, which could help to better isolate the cause of your problem. The only place I know that can read these codes is the Ford Service Centers, and independents often don't have the necessary tools to access them.

A replacement module costs ~$60.

I checked my wiring manual for the Windstar, and it showed that in addition to the GEM, the keyless entry and security systems could also play a role in causing your problem.

Tomj76, I think you are correct about the GEM. I have checked the state of my battery and alternator, all is well. I have made sure that nothing is hitting any of the switches. If you think about it and boil it down, the power lock system just consists of the door switch, fuse, relays, and GEM. Due to the fact that it is totally random with regards to which door starts going crazy (sometimes all four doors, sometimes just the right front, etc.) that basically rules out the door switch and relays because they would actuate all of the doors every time, right?

By the way, my van does not have either keyless entry or security systems. Thanks for all of your time tomj76.

Where can I get a new module for $60? I checked with the dealer this afternoon. They are discontinued from Ford. List price is $282. They can get one from a dealer in another state, but I would still pay $200 at least he said. $60 I would pay, but for $200 I think my van would just have manual locks from now on. By the way, I noticed tonight that my dome lights went off right away with the closing of the doors; normally it takes maybe ten seconds or so before it would go off. Perhaps another indication of an issue with the GEM??

I think I saw a few for sale on ebay. Also try Autozone, Advance Auto, Carquest, RockAuto...
http://www.rockauto.com/catalog/raframecatalog.php?carcode=1304648&parttype=2888

Well, I purchased a used G.E.M. for $65 and just put it in. The same exact thing keeps happening; no changes. That stinks. Now what? There are three different relays for the power lock system and the door switch. Just pick one of the two and change them out? Would there be a good way to test and see which one it is? I had the battery un-hooked while I changed the G.E.M. At the same time I put the power lock fuse back in. When I connected the negative battery cable back onto the battery, there was a "clunk" sound from the power lock system. I got in the van without ever putting the key in the ignition. I hit the lock button on the driver's door and they started going nuts again. I can hold down lock for a few seconds and it will stop. If I hit unlock, nothing happens. I hit lock again and it starts going crazy again. I unhooked the battery, pulled the fuse back out, and put my original G.E.M. back in. Bummer. One other side note: when this lock deal started, at the same time my dome lights started to shut off as soon as the door is shut, versus usually it stays on for a little bit. When I put the used G.E.M. in, I got in the van and shut the door. The dome light stayed on for awhile like it used to. When I put my original G.E.M. back in, now the dome light shuts off again right away. Thank you for anyone's thoughts.

I'll try my best to describe the door lock circuit... it's fairly complex.

There are three relays, located in the I/P Fuse Panel, each a single pole, double throw, and one terminal of the coils of each are continuously connected to 12 volts. The other coil terminal is connected to the control.

All the "motors" that lock or unlock the doors are wired in parallel, except for the sliding door, which is series wired through the "Memory Lock Relay" before connecting in parallel to the other motors.

One side of the motors is connected to the common of the "Door Lock Relay" and the other side connected to the common of the "Door Unlock Relay". Normally both of these relays switch to connect the common to ground. When a button is pressed to unlock the doors, then the Unlock relay connects its common to 12 volts from the battery. Likewise, when a button is pressed to lock the doors, then the Lock relay switches its common to 12 volts. In each case, since the other motor terminal is connected to ground through the alternate relay, the motor receives power. Note that if one control button is pressed to unlock the doors and another button is pressed to lock the doors, then both relays switch to 12 volts and the motors have 12 volts on both sides, and no action occurs.

The "Memory Lock Relay" appears to lock the sliding door (but not unlock) the door under control from the GEM.

The door lock control buttons are double pole, double throw switches that alternately connect one of the commons to ground. These are also wired in parallel. The DPDT switch has two commons, one connects to Door Lock Relay coils and the other connects to the Door Unlock Relay coil. Since the other terminal of the coils is always connected to 12 volts, pushing the button should cause one of the relays to close.

Since your doors are spontaneously switching both ways, I can't see a single point of failure in the schematic that would cause this symptom. However, I doubt it is due to a bad relay. First, relays normally fail by NOT passing current when connected. You have the opposite condition. Second, you'd need two relays to fail in the exact same way. Just to check, you might be able to swap the Door Lock Relay with the Memory Lock Relay. If the symptom changes so that the doors only unlocks randomly, then replace both of the relays.

It seems more likely that a short is occurring in the control circuit. I think it's unlikely that you'd have a short condition in both wire circuit leading from the switches, but it is possible that one switch is bad, alternately connecting the coils to ground.

Note that if you had a permanent condition on either relay (i.e. always connected to 12 volts, or always connected to ground) then you would only be able to switch the door lock in one directly.

I have just been going without power locks for several months now. I took my van to a friend who is a retired body man so he could adjust the hinges on my drivers door. While there, I mentioned my power locks issue to him and he said that he would check it out. You will never guess what it ended up being. He took the key and went around the outside of the van to check out all of the locks. On the passenger side sliding door, he could turn the key one way, but not the other. He played with it for a little while and got it freed up. That was it! A couple thoughts here: either the lock was stuck and somehow the system knew that door lock was not going up, so it kept trying every second, or it is maybe something with the timer function on that door. If the door is open and you hit the power locks, after the door is closed the computer completes the function on that door then. Not sure. Crazy. Sprayed some Tri-Flow lube on everything and it has worked great since!