The Impossible Hyster

Mr.Ferguson · Sep 1, 2018

I have a hyster z90 telehandler, don?t know the year. I know this is for tractors, but the hyster (hence the name) is doing the impossible. It is charging the battery, even though the alternator is not hooked to the battery. In fact, the whole harness isn?t hooked up, and 2 out six gauges work! It truly baffles me!

Slightly on the concerned side, Mr.Ferguson

pms · Sep 1, 2018

Hook a voltmeter to the battery while it is running.Assuming it's a 12 volt starting/charging system if meter shows 13 or more volts one way or the other that alternator is charging the battery.If 12.5 volts or less then you are probably right and before long you will have a dead battery.

NCWayne · Sep 2, 2018

I had something similar happen on an old Traverslift telehandler. If the exciter wire to the alternator is hooked up, and working to excite it, then it's possible to back charge through what of the electrical system is there, if the diode that's supposed to be in that line is bad, or missing.

In my case it was keeping the fuel solenoid pulled in, even when the switch was turned off. I put a new diode inline and it solved the problem.

Hope this helps.

Mr.Ferguson · Sep 2, 2018

Hooked up a voltmeter, and is charging. But it no connection to the alternator. None!

tn terry t · Sep 2, 2018

(quoted from post at 01:01:20 09/02/18) Hooked up a voltmeter, and is charging. But it no connection to the alternator. None!

whats you voltage reading ?

oliver power · Sep 2, 2018

I've seen an 8 cylinder gas engine in a pick-up truck rev so high, I thought it was going to blow. Turn the ignition key back off, and it continued to rev, as if I held the peddle to the floor. (Now here's the unbelievable part) I yanked the coil wire off, and it continued to rev. Yes, that's right. The engine ran with no coil wire going to the distributor cap. Had to choke the engine, in order to shut it down. So yes, back feeding electric is possible. Would have NEVER believed it if I didn't experience it myself.

MarkB_MI · Sep 2, 2018

One thing I've learned over many decades of electrical troubleshooting is that if something doesn't make sense, then you've overlooked something and you need to back up.

First off, unless it's a self-exciting alternator, it can't charge without a field connection to the battery. I would check the voltage of the alternator output terminal relative to the alternator case. That will tell you if it's actually charging or not.

Now the alternator is not necessarily the only possible power source. The most obvious candidate is the starter. If the starter drive is stuck, the starter will get "motorized" and become a generator. It's not going to last long if that happens!

gene bender · Sep 2, 2018

Are you sure the starter isnt a starter-gen combination

centash · Sep 2, 2018

Must be making an internal connection through the alternator frame and sending current to ground....somehow...
Ben

teddy52food · Sep 2, 2018

Does it have a charging system with magnets on the flywheel?

guido · Sep 2, 2018

Hello Mr Fergusson,

No it is NOT charging your battery, it is not connected! It is not a wireless system. You need to make some voltage checks and post them. Any noise you hear while the engine is off? Normal battery voltage is 12.6 volts @ 80 * F* while charging volts is between 13.8 to 14.2 V. Some newer vehicle run a bit higher though,

Guido.

K Effective · Sep 2, 2018

Dang, he's invented the perfect, perpetual motion machine and you guys are trying to "fix" it!

MarkB_MI · Sep 3, 2018

> Does it have a charging system with magnets on the flywheel?

A little research shows these machines are powered by four-cylinder Perkins diesels, so probably not.

Is it possible it has been re-powered? That might explain the disconnected wiring harness.

The Impossible Hyster

Mr.Ferguson

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pms

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NCWayne

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Mr.Ferguson

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tn terry t

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oliver power

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MarkB_MI

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gene bender

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centash

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teddy52food

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guido

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K Effective

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MarkB_MI

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