I'm working on a few electrical bugs in a 91Z. Both door lock actuators do not work. When the door lock button is depressed, the 20Amp fuse blows. Replaced the fuse and changed out the door lock relay. Same thing, the fuse blows. When I test the actuators with an ohm meter, both show very low resistance, almost open. Is this normal? Or, should the circuit in the actuators show a complete loop? I'm guessing that it's replacement time but hate to throw parts at it if not needed.

Thanks for your input and comments.

 

Help? Anyone ever tested a power door lock with an ohm meter? Do they show low resistance or should the circuit be full?

 

What kind of resistance did you measure? You can try to search for the spec. I'd measure it for you but I'm not at home, I'm stuck in Florida right now.

You can disconnect the door lock relay and see if that stops the fuse from blowing. If not, then your problem is in the wires before they even make it to the relay or actuators.

You could also pull the actuator wires out of the relay connector (you can pull wire by wire with a tiny screwdriver) and see if the fuse still blows. If not, it'd point to the power-side harness or maybe the actuators themselves.

Let us know what you find.
Lou

Lou

 

Lou, Thanks for the tip's and advice. I'll try all of them.

Dont remember the exact ohm reading but it barely moved the needle off the zero. If it was an open, I'd just replace the part... which made me wonder if indeed that's normal?

btw, I'm using the interior wiring schematics you helped me with and they've been great!

Thanks

W

 

Dunno if it'll help but I can try to snap some pics from my service manual of the door lock diagrams and trouble shooting steps tomorrow fr ya.

 

The power locks have two power circuits. The 20 A fuse supplies the relay coils in the Door Lock Relay only. If this fuse is blowing each time you operate the power lock switch, then you have a short in either the Light Blue LOCK circuit or the Black UNLOCK circuit. Note that the circuits are commoned at the the Door Lock Relay Terminals. The LOCK circuit goes to terminal A and the UNLOCK circuit goes to terminal B. Both of these circuits are connected to the relay via connector C217. Note that the orange wire from the 20 A fuse to the door lock switches is always HOT.

The second circuit is the Power ACC circuit and it is supplied via a 30A Power ACC circuit breaker on the fuse panel. This circuit powers the door lock motors to lock or unlock the doors, via a contact in the door lock realy. This circuit is also hot at all times to the door lock relay terminal A via an orange/black wire. Make sure this circuit braker is closed to provide power to the door lock motors (acutrators).

The acturator is a DC motor so its internal resistance will be low, as you noted. Make sure you disconnect the acturator before putting the ohm meter on it, so you don't include other parts of the circuit.

Hope this helps you find your problem

Dave

 

Dave, Thanks for the specific info! I havent yet had a chance to get back to the problem / project but you've certainly helped narrow the search. The 20amp fuse is the one that shorts when the door lock switch is pressed to lock or unlock. Kind of points me to a bad ground (black wire) I suspect?

I did disconnect the lead to the actuator motors when testing with my ohm meter, sounds like low resistance is normal. That's also good and useful info.

Thank you one and all that have take the time to post and assist.

 

No Problem. I started a new job today and will be flying to Boston on Wed. to attend my aunt's funeral.

The Black wire metioned in my first post for the UNLOCk cicruit is not a ground connection. (Yes Black is normanly used as the ground circuit in these cars). The ground appears, from my service manual schematic, to be directly connected to the door relay.

Good luck, and let us know what you find or if you have further questions. I will be on the road through Sat., so it may be a day or two before I can post a response.

Dave

 

If you say the problem is in the control circuit and you already replaced the relay, then I'd test it with the relay removed. If it still blows the fuse, it's either the switches, wiring or relay connector.

Does the switch on the other door blow the fuse too?

Does it short on LOCK or UNLOCK only?

Does it short when you just press AROUND the switch? Maybe the orange power wire behind the switch is stripped and when you push on it, it touches ground.

If you rule out that it's not the switches then you can move onto the harness. Disconnect the switches and the relay too. Then measure resistance (against ground) on the black wire on the switch connector. Same for the light blue wire. You should see open circuit, meaning highest resistance possible. You shouldn't see 10 Ohm or 0.1 Ohm or anything like that. That would be a wiring problem.

Let us know what you find, it's got me curious.
Lou

 

FWIW a common problem for power windows and locks is the wire bundle that pass through the door jam. After this many years of opening and closing the door I have found wire will break and/or crack causing shorts and opens.

 

ok, so I hate to sounds dumb, but I am new to all of this.

where is the door lock relay? and roughly what does it look like?

any help is appreciated.

 

Welcome to the boards. Please don't feel dumb, you only learn by asking questions

So take a look at one of the diagrams I just posted in this thread. The first image on the left will have a picture of where the relay is located. Note that you probably will have to remove the hush panel under the steering wheel and then the kick panel on the left side of the driver's compartment just in front of the driver's door to access the realy.

I suggest you right click on the image and "Save AS" to your computer. Then open the file in some picture viewer software so you can rotate and zoom in to read them.

Look here:

https://www.thirdgen.org/forums/elec...rritation.html

Note that you will have to rotate the diagram 90* to the left to view it correctly.

Dave