Gearbox Solenoid Repair
 

UPDATE: 03/10/15 - please see post #17 before carrying out this repair !!!


As some will know, X702UOK was showing very harsh gear changes on it's first drive last week - so much so that I'd be 90% certain that this is why it ended up at the breakers, as realistically it was almost undrivable. However, many kind souls on here (you know who you are ;)) have been offering advice and pointing me in the direction of the '2/4 brake duty' solenoid.

There's plenty on this forum already about how common this fault is with the autos, how to check it and how to remove and replace the faulty solenoid with a new one (so I won't go over all that again). But as the weather was decent today and the broken one had to come out anyway, I thought I'd try to find the fault rather than just bolt a replacement straight in.

On closer inspection, it turned out there was a tiny fracture in the earth tag, inside the solenoid, meaning the current to operate it couldn't get through. One small blob of solder and a bit of reassembly later and I'm pleased to say the gearchanges are now beautifully smooth once again :}

1) So, with the solenoid removed from the gearbox, this pic shows how the metal end was held in place by four press-tabs around the outside of the case. These had to be carefully eased back (I used pliers then a small screwdriver & hammer on a vice). This allowed the metal end piece to be removed:

Attachment 44947

2) This shows how once the tabs are pushed back, the end and central shaft will lift out - mine had a tiny washer stuck with oil to the end of the shaft, so was careful not to lose it. I used a small screwdriver to tweak this whole piece up, as it was still a little tight around the edge of the case:

Attachment 44948

3) With the metal end removed, I could now wiggle out the plastic cover (shown on left of pic, it's just clipped in, I used a small screwdriver to carefully prise it up) then underneath this are the electrical pins. The centre one (earth tag attached to solenoid case) had sheared right where it goes into the plastic - high stress point due to constantly vibrating I suppose ? (Note that in the pic, I'd bent it back to try and get the centre out, but didn't actually need to).

Attachment 44949

4) Having cleaned up the pins with some electrical cleaner (and bent the earth tag back down into place), this shows the solder used to repair the break:

Attachment 44951

5) And lastly, I reassembled everything in the opposite order that I'd taken it apart, ensuring all parts were kept clean. I used an old copperslip tube lid to press the metal end back into place in the vice, then used molegrips to squeeze the side tabs on the solenoid case back into place. Once held snug, I finished off by using the hammer and screwdriver again, just to ensure the tabs were 'fully home':

Attachment 44952

I appreciate that I can't guarantee this repair in the way a new part would of done, but only time will tell and it saved around £60 in parts alone.

And who knows, one day the solenoids may become NLA... :eek:

Cheers :}

Nice job. Haven't seen one fail there before, it's a part of the coil which had gone on a few ive seen so obviously irreparable.

Hopefully the repair will last a while

Nicely done sir, and good how to as well.... I wonder how many have bought new solenoids for want of a blob of solder ;)

does anyone know what a good coil should meg out at?

I did but still got the old one so I'll repair it and keep as a spare :D

What?
:puke:

Pete, I know that you are capable of expressing yourself perfectly well without resorting to these depths. :o

Here's a translation into technical English:

"Does anyone know the DC resistance of a good solenoid?"


:getmecoat:

Simon

Congrats :}

Always a pleasure to know how it works , why it has failed and
can be repaired ...at low cost

Mike

What resistance should I see if I where to put a MEGOHMETER across the coil and test it...

something like this...
http://www.the75andztclub.co.uk/foru...7b5ad2f923.jpg

it puts a high voltage low ampage pulse through the coil and if the coil is broken the reading will deviate from the expected range...

Pete,it not a megohmeter you need
for a coil is simply a length of copper wire :}

In Megohmeter mode you can test the insulation between coil and body.

Mike

yes, but would it not show a break or damaged coil the same as a squirrel cage motor.... we do check solenoids and motor coils at work and it does identify issues like damaged insulation, just wondered if anyone had tried...