Help with Door Ajar sensor

[L.U. Cifer]

Whilst trying to figure out my recent "Help! I'm Driving Inside a Pinball Machine" problem (I'll probably be posting about that later--door locks clacking, bells ringing, and lights flashing, whether running or not, as long as the battery is connected), I found my driver's Door Ajar sensor wire was exposed and "grounded" against the window track. How does that thing work? When it is grounded does that indicate the door is closed? That would be my guess since I don't REMEMBER my Door Ajar light staying on when I'm driving. 1995 Explorer XLT 2WD.

Thanks!
TW

 

[Mbrooks420]

It’s a switch. It shouldn’t go to ground. It goes back the the GEM, or another computer.

 

[L.U. Cifer]

It’s a switch. It shouldn’t go to ground. It goes back the the GEM, or another computer.

Hmm. There is but a single wire, and a single connection, that I’m referring to. It plugs into the lock mechanism on the upper left corner with a Y/BLK wire. The PURPLE/Green wire that is bumbled with the other wire split off to a connection on the upper RIGHT corner of the lock mechanism. Is it a switch with 2 separate connectors? Or am I looking at a different device/connection?

 

[L.U. Cifer]

Hmm. There is but a single wire, and a single connection, that I’m referring to. It plugs into the lock mechanism on the upper left corner with a Y/BLK wire. The PURPLE/Green wire that is bumbled with the other wire split off to a connection on the upper RIGHT corner of the lock mechanism. Is it a switch with 2 separate connectors? Or am I looking at a different device/connection?

It appears the purple/light green wire goes to the Door Handle Switch.

My electrical knowledge is only a small step above “it’s fast, it can kill” but it appears both wires (one to Door handle Switch and one to Door Ajar Switch) are grounded when either of those switches are closed, sending that voltage back to the GEM.

Does that seem to be accurate? Don’t mind being told I’m wrong!

Thx!

 

[Mbrooks420]

If it’s a single wire, you must be correct. It must supply the computer with a ground.

This would be an NPN type of input, where a more traditional input would want to see a voltage (PNP style) an NPN is provided a 0v signal to trigger it. This makes sense as you don’t have a second wire requirement, and if it shorts out it just triggers and input, and doesn’t blow a fuse, or be a fire hazard.

 

[J_C]

I suspect you have a couple different things going on as stated.

The GEM produces a reference voltage. If the wiring is good, and door properly latched shut, switch working properly, a closed door closes the circuit, completes the circuit to ground through the door latch, so there is only a single wire to it needed to do that. The GEM senses that its reference voltage was pulled down with the door properly shut and all related parts functioning.

You stated you found the wire shorting out but that would only (momentarily, not dependably) cause the GEM to think the door is shut, while you have the opposite situation where the GEM seems to think the door is open when it isn't, so you have either a latching issue or the switch itself is failing, or the wire is frayed if not broken, so the switch is intermittently (if ever) failing to short the wire to ground when the door is shut, causing the bell and lights to come on.

See attached wiring diagram. A multimeter would be handy to check continuity between the switch terminal and ground in the latch shut state, and test continuity between the wire to the switch terminal, and the GEM to see if it might be frayed apart in the door hinge, boot area which is another common fault.

Another possibility is the door is sprung or misaligned and the latch is not fully closing so it is not fully depressing the switch to close the circuit to ground. I suppose if your door latch striker sleeve is shot, or the latch mechanism itself is falling apart (latch itself is probably the least likely of all alternatives presented) it might also cause some play and the same result.