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Post by tonymark3 on Oct 8, 2020 9:16:45 GMT
I have replaced 2 M35J starter solenoids in a matter of months. The first was the original as fitted in 1972. The second was a new old stock military one from John Richardson surplus, and was sealed in packaging in the usual military fashion.
When removed and tested on the bench it worked after a fashion - i.e. it pulled in but not to the full extent to operate the contacts.
I have ordered a modern replacement solenoid from Autoelectrical.
Question is- what causes the failures? Is it old age causing the varnish on the coils to fail? Why does it partially work i.e. weakly?
To end, a confession. I said to Chris i had stripped and rebuilt the starter. Not true. The one I rebuilt was from a Maxi But my failing memory thought it was from the 1800. Completely stripped the M35J and as Chris found, absolutely full off heavy duty crap. Works a treat now and checked the brush lengths and still good.
Last thought, I wonder if the solenoid WAS working, but motor wasn’t kicking in would extended operation cook the solenoid?
Tony S
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Post by tonymark3 on Oct 8, 2020 13:19:22 GMT
Answered one of my own questions.
Resistance of solenoid coil should be less than 5 ohms according to research.
All my solenoids showing 9 to 10 ohms so presumably all duff.Found another M35J in my shed but solenoid also duff. Motor good though so will purchase another solenoid o make good spare.
Tony S
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Post by Penguin45 on Oct 8, 2020 17:58:00 GMT
The only circuit should be through the coil on the solenoid itself - 5Ω sounds reasonable. I've had one fail open circuit, suggesting that the coil has failed completely. The resistance being higher sounds odd - very dirty terminals perhaps? When energised, the resistance across the big terminals should be zero. Dirty or corroded contacts will show resistance, affecting the current flow to the motor. See also David's MULTI METER THREAD. Anyway, they seem cheap enough. Have you noticed that you can't find one with the red button on any more? Chris. |
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Post by tonymark3 on Oct 8, 2020 18:15:30 GMT
Yep. Checked them on the bench and they all will pull about half way. Take the spring off and they pull all the way in, so just weak.
pain but will see what replacement solenoid is like.
Autoelectric do a 2M100 but I think that has a 10 tooth gear. I shall phone them out of curiosity.
Tony S
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Post by dave1800 on Oct 9, 2020 6:24:05 GMT
The BL w/s manual AKD 4138 1977 under general data 16 shows the following information:
Lucas M35J Solenoid Resistance 0.9 - 1.1 ohms current 9-11 amps
Lucas 2M100 Solenoid Resistance 0.76 - 0.80 ohms current 11.2 to 11.8 amps
Lucas M418G Solenoid Resistance 0.63 - 0.73 ohms current 11 amps
Given the work the solenoid has to do I think these figures are probably accurate. If your solenoid measures more on your meter to be certain of the value wire a headlight bulb in series - it should be only slightly dimmer. It can be difficult to get an accurate reading of low resistance values with a multimeter. If it is 5 ohms or above the light will be significantly dimmed. A high resistance reading suggests the wire terminations are fouled.
David
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Post by tonymark3 on Oct 9, 2020 11:43:47 GMT
Thanks David.
Is it worth dismantling the old solenoids and resoldering the wires? Not being tight , would just like to retain originality.
Tony S
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cybercontroller
Member
Posts: 107
Attribute: Waiting for the right Landcrab
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Post by cybercontroller on Oct 9, 2020 13:14:52 GMT
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Post by dave1800 on Oct 9, 2020 14:16:56 GMT
Certainly worth a try. Hopefully the copper wires and insulation are still in good condition. David Thanks David. Is it worth dismantling the old solenoids and resoldering the wires? Not being tight , would just like to retain originality. Tony S |
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Post by dave1800 on Oct 9, 2020 14:24:15 GMT
The coil may give 20% more spark energy, but the BMC A and B series engines are quite happy with the standard coil and don't require any enhancement in standard tune. The add seems to suggest 20% more power which is nonsense, you won't notice any if your current coil is in good condition. Not a bad price for a spare coil though. David |
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Post by tonymark3 on Oct 9, 2020 18:36:22 GMT
Stripped M35J solenoid and resoldered all connections. Works a treat on bench.
Dry joints?
Will try resoldering the joints on the other solenoids I have without dismantling just to see. If not i can take them apart.
Warning - workshop manual AKD4138 issue 1.Pages LA11 and LA13 the starter diagrams have been transposed. LA11 depicts a 2M100 but the legend states M35J. Had me scratching my head for a minute.
Tony S
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Post by Penguin45 on Oct 9, 2020 23:06:26 GMT
Ah. I have the 2M100 without solenoid or pre-engagement mechanism. That isn't in the WM at all! See comment in resto thread.
Chris.
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Post by tonymark3 on Oct 10, 2020 15:25:14 GMT
Well I am learning all the time. A really good explanation of solenoid workings here www.mgb-stuff.org.uk/stasol.htminstalled the new solenoid on the starter and bench tested. Works a treat. Install tomorrow. Having read the guide (above) I now realise the pull-in coil earths through the starter motor connection . I now wonder if the problem was a poor earth due to all the crud etc in the motor. If you test the solenoid Off the motor by connecting the battery to the switch terminal and earth to the body You only operate the hold-in coil, which has insufficient power to pull in. Every days a school day. I am sure the wiser ones amongst you will have a chuckle, but as usual I have learnt from my mistakes. Tony S |
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