Actuator Testing

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Mar 13, 2003
North Front Range, CO
I need to test the rear diff actuator before I try and have it welded.
The FSM says to use a 'heater main relay' to test the actuator.
Why do I need to use the relay?
Can I test it another way?
I've heard of guys using a little 9v battery to test it. Does the FSM say what voltage is going to the actuator?
There is voltage from the wire harness and ECU but I can't tell the volts are to the actuator.
From the EWD for my '97 it looks like you want to put +voltage to the green wire to go one direction, and +voltage to the green/blue wire to go the other direction. The limit switches in the actuator opens or closes either the green/black wire or the green/yellow wire to complete the circuit.

ECU changes directions by switching the +12v to the proper motor wire depending on which direction you want to turn the motor. The EWD doesn't make it clear to me which direction the motor will turn; you'll have to figure that out for yourself.

It looks like you want to hook the -voltage from the 9v battery to the White/black wire. The diagram is on pg 155 for someone that has a scanner. I can take a pic of that page and post if you need it.

When u pull the rear diff elec connector u are left with the female plastic connector that has 5 male pins. With this up straight (i.e. inverted U tab at top) apply + and - to pins 1 and 2 on bottom left. Doesn't matter which way u apply the Voltage as if nothing happens just reverse it. 9V little alkaline battery (new) will work for the motor if its all in good working order. In not then u have to use 12V. Don't leave power on too long - max 3-4 secs.
If u don't hear anything when tried both ways (switching around the Voltage) then it may be stuck! Give the motor cover (top left of housing - and thats after u have taken off the protector shield cover) a tap with a hammer and try again. If after a few attempts and nothing then u may have to disassemble it and see why its sticking.
If u get that far and need help give me a shout. I've plenty of pics and war-stories on my rear (fixed) diff :)

"Give the motor cover (top left of housing - and thats after u have taken off the protector shield cover) a tap with a hammer and try again"

A true mechanic, percussion maintenance!!!
[quote author=Beowulf link=board=2;threadid=8727;start=msg75272#msg75272 date=1071293225]
From the EWD for my '97 it looks like you want to put +voltage to the green wire to go one direction, and +voltage to the green/blue wire to go the other direction.[/quote]

That's wierd. I read about the 9 volt battery test on some mini truck dude's website and it states to use the green and green/red...and that's what I've been using. Just this week me and Mike B and Cody M just tested my second diff actuator for the first time (I bought it back in march...) Anyway, it was the green and green/red wires on it--and on my other one. I wonder if the wire colors were changed or something in the later years... I can't remember what years mine are from...but I believe they are a '94 and a '95.

Anyway, when we were testing this one last week, we thought we had a good 9 volt (I made Mike stick his tounge on the terminals a couple times to check it :D ) Anyway, we got nothin'. No movement. Pulled an old car battery that we thought was good and still got nothin'. Then we went and opened the hood of Cody's 40 and tested it on his battery and Voila! it worked great. I then went and pulled a brand new 9 volt out of it's package and tried it and Voila! it worked too. So my 2 cents is to make sure you have enough voltage.

The pin numbers in the '97 EWD don't match what LAL posted. Maybe there was a wiring harness change?

It's good to have someone confirm that the 9v battery test is valid. Thanks!
I tested it and it doesn't work.
Took it apart and the magnet got broken.
I am now stuck with the Downey cable locker :(
regd the pin layouts remember that the layouts in the manual relate to one side (male or female, I can't remember which). I know from pulling the connector that the connector plug that actually connects to the diff has the pins 1 & 2 (bottom left) as the ones that turn the motor (done it tooo many times)

Kurt - if the magnet is broken u can easily fix that (mine were loose and was able to re-epoxy). If really bad then u can get replacements (from an good elec repair store or maybe Napa?)

With replacing the magnet,welding the housing and having a new rod made, as that was bent too, and then it still might not work. I think I am done with it. The cable locker is working good anyways.
I'll just keep it for parts next to the broken t-case.

I think it would be a big benefit to the diff lock community if you could document a cleaning/disassembly procedure along with some detailed pictures. Yours looks perfect inside but we occassionally get people asking about how to "clean" their sticky actuators. You've done 99% of the work so a quick write-up could make you immortal in the 80 series world....

... not that you aren't pretty close to being a legend already with all the X-fer cases, the spare parts inventory; and the (shhhhhh) leaks :D

Maybe Santa will bring you a new digicam?

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