P38A Stuck in Low Range Again

JamesBB said:

Here is an update.

The secondhand ratio motor I bought is dead. No movement at all. When I apply volts directly to the motor (either way around) there is no movement, just a small spark. So I guess it is seized.

I rotated the TB spindle manually while holding the output shafts (one at a time), as soon as I feel it free up I feel a very slight knock through the output shafts. I guess this is the cam moving the forks forwards to engage Hi (I hope). I guess the only way to find out is to drive it.

I have asked for another replacement motor, but I am thinking finding one that works off of a scrapped car is a gamble as they are all so old, and hardly ever used when the car was working. Hence chances of being seized.

When it comes to fitting another motor I think you are right, find high manually, plug motor in, start up, select high, switch off, and bolt-on motor.

I will update again when time permits. Cheers for the encouragement.
Jams

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Grrrrrr said:

Never had an issue in any of the 5 I have driven or the current 3 I have access to. On that basis I would say one for a scrapper should be fine unless something in your setup is causing the motor to draw too much current and burn out.

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Grrrrrr said:

Never had an issue in any of the 5 I have driven or the current 3 I have access to. On that basis I would say one for a scrapper should be fine unless something in your setup is causing the motor to draw too much current and burn out.

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Mark Piercy said:

That's because you use the lowrange and keep it exercised

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Mark Piercy said:

I use the low box for pulling cars around the land and in the rough terrain

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Datatek said:

It's good for reversing with the caravan in tight spaces too

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DanClarke said:

I think the OP's problem highlights the "use it or lose it" nature of the Hi-Lo feature.
I rarely need to put mine in the Low range and maybe it ought to be a "monthly task" just to ensure the mechanism doesn't stick.
Keith, even though it is driven by Mosfet power transistors the Voltage is still 12V or thereabouts isn't it?
So if the OP has tried a change motor against a 12V car battery in either polarity and it doesn't work/is seized is that not a valid test?
I mean, its not a motor driven by a PWM signal is it?

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Datatek said:

@DanClarke Yes 12 volts direct is a valid test. Usually it's the iron rotor segments rusted to the iron field segments that causes them to seize I'm told. A strip down would sort it most likely.

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Grrrrrr said:

Is there a way to squirt Plusgas in anywhere and then just jiggle the shaft back and forth until it frees and then blow it out with an airline?

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JamesBB said:

Hi Guys
Sorry for the silence on the progress. Here is an update.
While waiting for another replacement motor I decided to strip both down clean them up and make 1 good out of the 2.
Both had broken plastic/rubber (whatever it was) spacers around the end stop screw.
I fitted a small black rubber grommet of a similar size over the screw as a test replacement. Put on a blob of grease (as seemed on the original), greased the gear, and reassembled.
Applying power (each direction) and it spins freely and looks healthy.

I used the other donor motor's main gear as a tool by marking with a permanent marker along the shaft where the spindle is pointing (gives an indication of position). Then as it is far easier to turn the main TB spindle with the gear, I found rotating fully clockwise put it into Hi range. Tested by driving it. Diags still told me it's Lo. I decided that was due to the lack of live info from the motor, which was not connected at all. I connected the motor electrically, started and changed ranges, it possibly fooled the motor into supplying feedback to say it was Hi.

The marker line I made allowed me to see the position/direction (approx) the motor should be pointing in when bolted back on.

At that point, I applied voltage directly to the motor again to spin it to the position I noted immediately before. Bolted back on and tested again.
It works. No select neutral message.
Changed into Lo again, all ok.
Changed to Hi, beep beep beep nothing.
Take motor off, realign to Hi manually again as above, re-fit motor.
Test, all ok in Hi, problem with Lo.
Hi or Lo is defined by the electrical contacts on the motor assembly. I very much doubt the problem is internal to the TB as you can select both Lo & Hi. I would bet that the timing between motor, TD and contact assembly is not correct.

The TB can be moved to Lo or Hi manually, it drives fine in either mode. So I guess it is ok in general and suspect the problem is either a weak motor in one direction or maybe the selector fork on the end of the cam inside the TB is maybe worn or gummed up. Apparently, it is only plastic.
The next plan is an oil change and see if it helps at all. It has not been changed in a very long time.
In the meantime, I have now received another motor which seems strong in it's behaviour testing off of the car.

Update soon. Efforts changed to underside rust protection at the mo.
Cheers

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