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I have a Z4000 with the "short light" staying on continuously. Everything is disconnected, power cycled but no change.  The right handle seems to have an mechanical issue, something seems to be rubbing/interfering - I assume something got loose. Any tips on how to take the cover off and tinker with the handles? I am not finding much on the forum or web in general except send it in.  No smoke no arcing seen, just the red light came on.  The aux power still provides voltage - have not put a voltmeter to the track outputs, I'll check this,  but pretty sure nothing coming out.

Thanks for any insights -

Got the cover off. One of the cover screw mounts had broken off and was rattling around, but that was not the issue. As it turns out the right hand handle was nothing more than the adjusting screw accessible from the underside had gotten loose to the point the handle gears did not engage with the pot. A little adjustment and the handle works fine.

On the other hand the transformer still shows a short. I could not see anything burnt, melted or discolored. Ill have to decide whether I want to send it in for repair or try to find a used one.

You need a long hex or torx bit to unscrew the cover. Screws were in hand tight so not a big deal to remove the cover. There are several wiring harnesses which connect to the cover so be careful lifting the cover, they need to be separated to get the cover completely off. I do not think there are any user serviceable parts in there so not much point in trouble shooting unless you have a guide and the diagnostic tools. 


Last edited by ScoutingDad
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If the z4000 throttle gear has slipped inside and is not fully closed you will get a short light! the metal bracket sometimes get bent and the gears slip off each other and get out of time. there not easy to take apart and I would not recommend trying unless you know what your doing , you can damage the unit inside and the harness's are very short and easy to pinch a wire !

also MTH will only sell transformer  parts to ASC TECH's


Last edited by Alan Mancus

Have to remove all the allen screws from the bottom of transformer.  Metric.  Some may have been phillip depending on production run.  Handles up and top comes off.  Need to observe where harness go and how they are oriented on top.

As far as handle there is a set screw on bottom of handle on later models to control friction on handle. G

Z4000 repaired!

Once again thanks for all of your replies.  Turns out the right handle worked itself loose and only partially engaged the throttle gears. Once that happened the potentiometer would not rotate to the zero position. The Z4000 would turn on but not leave the "short" status.

This Z has set screws to adjust the handle tightness on the underside of the case. I guess one had worked itself loose and allowed the gears to slip - causing the problem. Z4000 internal

The contact between these two white gears is adjustable through the set screw. Backing it out most of the way  I was able to rotate the smaller gear to a zero or off position without moving the handle gear. Once set, the handle was rotated to the off position and the set screw re-adjusted bringing the gears back together to mesh. Since both potentiometers were now at zero, the Z started up normally. Funny how something so simple causes the Z to stop working - I suppose its a safety feature.  In my opinion this gear design provides a lot of sloppiness in fit and ensures the pot will eventually work its way into a non-zero position and show a fault. Expensive to ship and repair - and unnecessary since nothing is really wrong with the transformer.   

Z4000 handle

CAUTION - as mentioned in the comments, the wiring harnesses do not leave a lot of room to move things around, be careful in lifting off the cover. While you can disconnect the harnesses from the cover you really do not need to do so in order to re-align the pot gear. You will need a long hex key (allen wrench)  to remove the 7 screws holding the cover on. Mine were barely finger tight.  Remember to pull the power plug before opening this up. I put the cover back on without the screws to make sure the pots were zeroed, powered it up to make sure it worked, pulled the plug and then screwed the cover back on. Also be careful on handling the cover and base, I find it is brittle and found some pieces broken off internally. 

Thanks to the following for their help

@gunrunnerjohn  @GGG  @Alan Mancus 


Images (2)
  • Z4000 internal
  • Z4000 handle

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