Last Nail in the Coffin?

[TurnThePage]

My '97 F150 has had its share of issues over the years. Starting last fall, if I use the keyfob to unlock the door, it gets stuck in a cycle of endlessly locking the door instead (click, click, click, click, etc). A smart slap to the door seems to correct that. At least momentarily.

Today, I went to start it (for the first time in a week or two) and found an EXTREMELY dead battery (2v). Hmmmm.. When I connect a charger, the horn starts blaring. What gives? I've disconnected the battery while I recharge it.

Why is the horn sounding when I connect the battery? Is this likely just the horn? Or is it rather something much more expensive?

[Gdetrailer]

BillyW wrote:
Well, it's been cold and wet/snowy, and I've been pretty busy, so no major work done yet. BUT! I've managed to recreate the original lock cycling problem while the GEM fuse was removed. Could it still be a short to ground in the GEM? The fuse is only on the hot side power to the GEM, right?

I would think that the GEM has only one fuse but you never know..

You could have sticking/stuck/bad relay perhaps.. But after looking at the wiring diagram I am not sure if the relays are at fault..

Door lock wiring diagram

DIAGRAM HERE

Door lock relays appear to be in the “smart junction box” which I suspect is the fuse box directly under the GEM..

From the diagram it appears that the door lock relay coils are hot or powered all the time. The GEM “grounds” (negative going signal) the relay coils to activate the relays. All it would take is a short to ground on the relay coil to engage a relay, water or rust from the relay to ground could create this short.

I am not sure if the door lock relays are replaceable so if you can't find them in the fuse area in the fuse box they may be internal and not replaceable without replacing the fuse box..

[TurnThePage]

Well, it's been cold and wet/snowy, and I've been pretty busy, so no major work done yet. BUT! I've managed to recreate the original lock cycling problem while the GEM fuse was removed. Could it still be a short to ground in the GEM? The fuse is only on the hot side power to the GEM, right?

[Fredzo]

My '96 F250 had the same problem about 8 years ago. Turned out that the module had a lifetime warranty from the supplier (to Ford), but that they had no rebuilts of that model available.

They sent me a new GEM with two new fobs, and all I had to do was change a couple of connectors, also supplied, and it cleared my problem.

I had to return the old module.

I can't, for the life of me, remember who the mfr. was.

[Gdetrailer]

BillyW wrote:
Yes, it appears they don't manufacture them anymore either. I haven't called a parts outlet yet though. I'll be cleaning and checking as much as I can before actually replacing it.

And by the way, the battery maintainer was slowly losing the battle too.

Step by step removal instructions

HERE

Doesn't look good for finding even refurbs but for some reason there is a ton of used GEMs on Ebay..

EBAY SEARCH

I am not too impressed with Ebay finds since you take a chance that the used GEM may be bad also..

Somewhere I read that they are kind of generic so you may have a little leeway in years as long as it has the same "build" fuse box and options like like 4x4, power windows and such.. Otherwise it would need reprogrammed by a dealer..

[TurnThePage]

Yes, it appears they don't manufacture them anymore either. I haven't called a parts outlet yet though. I'll be cleaning and checking as much as I can before actually replacing it.

And by the way, the battery maintainer was slowly losing the battle too.

[Gdetrailer]

BillyW wrote:
Well, Gdetrailer, you may be on to it. I had some time today, so I whipped out the trusty Heathkit multimeter and did a little testing. I have never used the amperage measurement function on it in the nearly 30 years I've had it, so I'm not certain of the readings. When I put it in the circuit, amperage jumped to nearly 1.5 amps then settled to .44 amps. Pulling the door lock fuse didn't affect that at all. When I pulled the fuse for the GEM, it initially jumped to about .8 amp before settling to .08.

🙂

.44A or 440ma is definitely a high draw which would be more than a battery maintainer can typically supply..

The .08A or 80ma with the GEM disconnected would be a much more realistic power draw when sitting..

So, now you are down to the GEM as the most likely suspect for the flat battery.. And since the GEM also controls the door locks I think replacing the GEM should solve both issues..

Not sure how easy it is but you might want to double check the harness connectors going into the GEM for any water, corrosion or even chaffing of the wires which could also cause problems..

[wecamp04]

We had an 2002 explorer had the door lock problem it would lock and unlock trying to get in ,got to doing it while driving that's when the interior lights started fflashing it did it .Traded it for a new 2010 much better.

[TurnThePage]

Well, Gdetrailer, you may be on to it. I had some time today, so I whipped out the trusty Heathkit multimeter and did a little testing. I have never used the amperage measurement function on it in the nearly 30 years I've had it, so I'm not certain of the readings. When I put it in the circuit, amperage jumped to nearly 1.5 amps then settled to .44 amps. Pulling the door lock fuse didn't affect that at all. When I pulled the fuse for the GEM, it initially jumped to about .8 amp before settling to .08.

[Skid_Row_Joe]

TNRIVERSIDE wrote:

donn0128 wrote:
Security systems often do that when the hattery is dead and then connected to a charger or other 12 volt source.

X2. I'm betting on the security system.

X3. He's got a dead battery and perhaps an out of control power drawn down on the battery when idle. Find a good electronics automotive shop, and hope for the best in their diagnosing and repair expertise.

[Gdetrailer]

BillyW wrote:
Gdetrailer, I'm familiar with that phenomenon and have paid attention to the possibility for many years. (At one point I actually thought it was the culprit of a random power window issue that plagued the truck for over 2 years. After visits to multiple mechanics and lots of $$$, the right one finally narrowed the problem down to a misbehaving relay.) In this case no leak that I can detect. I'm not ruling it out though. But when the lock is caught in its looping cycle, I can hit the door and cause it to stop. Do you think the BCM would cause the lock to behave in that fashion which quits after I strike the door?

On a side note, even though I've kept that cheap HF battery maintainer connected after fulling charging the battery, the voltage was down to 12.55 when I checked it this evening. That's with HF still plugged in.

Here is a photo of Ford’s door lock actuator (you will need to scroll down the post)

THIS LINK

In there you will find only several gears and a motor, the motor has a overload thermal cutout attached to it.

The thermal cutout goes bad and causes the actuators to get weak and no longer have enough strength to lock and unlock the doors.

That’s it. No other “electronics” contained within the door lock actuator which can cause it to continuously cycle.

Banging on the door is not really fixing the cycling problem at the actuator..

The door lock/unlock switch contains no electronics and typically since the late 1990s does not directly operate the door actuators but is routed to the BCM/GEM. The BCM/GEM then operates the proper relays to lock/unlock.

If you really sure that the BCM/GEM is not the problem with the doorlocks and the battery drain is not related then go ahead and throw parts at the problem by replacing the door lock actuators at about $70 each..

The battery drain is a well known issue with the BCM/GEM. The BCM/GEM controls pretty much anything which draws power. It has the duty of controlling all non engine/transmission electrical systems. It controls headlights/turnsignals, radio, doorlocks wiper motor, interior lights. It also has timer functions so when you close a door the interior lights stay on a few minutes and if you leave a door open it will turn the lights off after a preset time..

To find the drain and confirm if your BCM/Gem is either the cause or not of the battery drain you can do a simple test using nothing more than a 12V light bulb.

You can use pretty much any 12V bulb like a turn signal or backup bulb and a socket for the bulb or solder wires to the bulb.

You remove positive battery lead and wire the bulb in series with the battery lead (one wire of the bulb to the positive of the battery and the other wire to the wire you removed from the positive of the battery).

At reconnection your under hood light will relight and the bulb you have hooked in series should also light dimly..

The under hood light should turn off after 10-15 minutes and the bulb you connected in series should no longer glow.

If under hood light goes out and bulb you connected continues to glow you have a phantom power draw.

To find the phantom power draw you will now need to start pulling fuses.

Since there so many fuses it is going to take a while..

For a more accurate way of checking on phantom draws you can use an ammeter, most el cheapo DVMs tend to have a 10A DC ammeter function which as long as you do not run any high draw items will be fine.. If you don’t have a DVM or a DVM with DC Ammeter you can often get FREE DVMs from Harbor freight (with a FREE coupon) which do have ammeter function..

Insert Ammeter in series like the light bulb I mentioned above, DVMs can read current either + or (-) so for this test it doesn’t matter so don’t worry about a (-) reading..

To flatten a battery overnight I suspect you have a current draw of 1/4A (.250A or 250ma) to even 1A or more.. Your HF "maintainer" is pretty much a trickle charger at best supplying 1/2A or perhaps 1A (and that might be generous) to the battery..

There will be a very small draw from the stereo keep alive memory/clock power and the trucks computer and most likely the BCM/GEM. I have never measured it but I would suspect that normal draw should be well under .05A (50 ma) since your vehicle should be able to sit unused for several months without draining the battery flat.

If you really feel the BCM/GEM is not causing the battery drain here is a few other suggestions on what to look at..

I have run into some wiring chaffing issues under the dash on our 2006 F250 to which caused a real brain teaser that I have never been able to find and fix.. Try this one out.. Radio speaker on the drivers side only gets a loud buzzing noise when the vehicle is only in reverse and you have your foot on the brake!

After several weeks of being upside down on my head under the dash I gave up and CUT the speaker wires for the drivers side door at the speaker and the radio and ran my own speaker wire directly from the radio to the speaker. No more buzzing noise!

Another known issue is the door switches get gummed up and the result is your interior lights stay on until the BCM/GEM times out.. The door light switches are integrated into the door latch and the fix is to spray some lubricant into the latch.. Regardless the BCM/GEM will automatically shut off the interior lights after it times out..

Some other things to look for is sticking brake light switch, that one for sure can drain a battery overnight as well as can a brake controller malfunction..

Not sure of the exact years and models of vehicles but you may wish to inspect your Master Cylinder cruise control pressure switch.. T

There is a defect which affected many Ford vehicles from 1994 up to and including 2004.. This one was if the seal/diaphragm failed on the switch it would leak brake fluid into the switch and possible cause a short and fire.. I know my 2003 F250 was part of that recall..

Here is a listing of the recall..
HERE

HERE

The “fix” if you could call it a fix was to inspect the switch for leaking and if it wasn’t leaking a special “fuse” link harness was installed (in other words they left a “defective” switch in place!! If no leakage was spotted at the time of the recall service)..

A leak could short the switch and the fuse link would blow preventing a possible fire.. It is possible that yours could have a leak and is NOT shorting out but is drawing enough current to drain the battery but not enough to blow the fuse link or yours does not have the fuse link installed..

I would highly recommend that you check to see if yours was affected.. If you have any doubts on this one disconnect the wiring harness from the MC switch immediately, it will not harm your vehicle by having it disconnected just be aware that in doing so your cruise control will not deactivate when the brake pedal is pressed..

[TurnThePage]

Gdetrailer, I'm familiar with that phenomenon and have paid attention to the possibility for many years. (At one point I actually thought it was the culprit of a random power window issue that plagued the truck for over 2 years. After visits to multiple mechanics and lots of $$$, the right one finally narrowed the problem down to a misbehaving relay.) In this case no leak that I can detect. I'm not ruling it out though. But when the lock is caught in its looping cycle, I can hit the door and cause it to stop. Do you think the BCM would cause the lock to behave in that fashion which quits after I strike the door?

On a side note, even though I've kept that cheap HF battery maintainer connected after fulling charging the battery, the voltage was down to 12.55 when I checked it this evening. That's with HF still plugged in.

[Gdetrailer]

BillyW wrote:
I'm wondering if flawed door lock electronics coupled with a low battery could contribute to totally draining the battery. Since I've totally recharged the battery, I haven't been able to replicate the door lock problem. Of course, I haven't given it much time yet either. A frayed wire could be the culprit. Will investigate that too. Thanks for the input!

By the way I've heard from multiple people with late 90s vintage Explorers relating similar stories! Not just online either!

NO.

The door lock mechanism in the door is nothing more than a MOTOR, it contains NO ELECTRONICS in that motor other than a fuse link in case of overload or overheating.

It IS COMMANDED BY THE BODY CONTROL MODULE (BCM) or sometimes referred to as GEM (Generic Electronic Module).

The Body control module is located on the DRIVERS SIDE near the kick panel.

It is well known that the windshield on a lot of Fords trucks will develop a WATER LEAK ABOVE THE BODY CONTROL MODULE.

The Body control module often DRAINS the battery once damaged by a water leak.. It is also known for causing door lock problems, windshield wiper issues and even no radio..

HERE is one example of the issue..

ANOTHER ONE

ANOTHER ONE

MORE

MORE

This is a well known problem and is not the locks or battery..

[jrnymn7]

'Til recently, mine's been a great vehicle. Only other thing that went (a number of years back) was the daytime running lights controller. But now it's showing its age... time to say good bye soon 😞

[mchero]

ITS POSSESED! GET RID OF IT QUICK!!!! LOL