Starter motor wiring modification

[CovKid]

I still think its a bonus mod Bigherb, but like I say, with most of these vans now 30 years old now and few with any changes made to the existing cables and connections, I'd still be making sure they're in good nick before/whilst I chopped in a relay. I mention this because the main cable on mine is already corroded (acid corrosion) if not brittle, no matter how far you chop back, and its impossible to get a good connection when its as bad as that. Its also the most expensive to replace due to its size and because of the job it does, prone to this kind of deterioration. Any reduction in efficiency in that cable reduces alternator output and starter responsiveness.

I dread to think what the voltage drop is like as mine has to run a good two metres with the battery in the front. Much of it only came to light when I had to change the starter motor recently. The ends looked fine at a casual glance - until you looked closely. I wouldn't be surprised if the smaller cable from battery to fusebox isn't far behind. Either way, they're going.

Heres the new fat one to the starter - ready for tomorrow.

[kentishvanman]

Hi,
Thanks for all your input fellas.
Don

[California Dreamin]

Bigherb.....the name given to modern starter motors is 'Pre-Engaged' (gear engaged before the motor is powered). The successful meshing of the pinion is down to two things 1) the lead on the front of the pinion teeth and 2) the rotation of the pinion created by a spiral gear/sleeve that the pinion and one way clutch mechanism are mounted on. As the pinion gear is pushed forwards by the solenoid it turns mechanically on this sleave, the main starter armature remains static until the pinion meshes and the main contacts are bridged.
I know it's a bit more complicated than that...(pull in coil initially drawing high current until the main terminals are bridged, cancelling out the ground for the pull down side leaving the secondary 'hold down' coil to keep the main terminals bridged.

Although this pic isn't of a Bosch starter you can clearly see the spiral sleeve that creates this rotation.



I respect much of what you write, however, I am unsure of the quoted 32amp figure given to the 'initial' solenoid operation ....it just seems very high, where did you get this info from?
I quite happy to be proven wrong..as I usually am lol.

Martin

[bigherb]

Yes I know they are called pre engaged starters and their methods of pre engagement.
As we are talking about Bosch starters fitted with powered rotational engagement fitted to our vehicles. You will see that the solenoid pull in (closing ) coil on Bosch starters earth's through the motor brushes and two field coils to slowly turn the starter, if it can't find an good earth through the motor it won't work.

[California Dreamin]

Yes I know they are called pre engaged starters and their methods of pre engagement.
As we are talking about Bosch starters fitted with powered rotational engagement fitted to our vehicles. You will see that the solenoid pull in (closing ) coil on Bosch starters earth's through the motor brushes and two field coils to slowly turn the starter, if it can't find an good earth through the motor it won't work.

Powered rotational engagement? as I said, the spriral sleave ensures rotational movement of the pinion as it is thrust forward into mesh with the ring gear.

According to your printout, the starter motor does not 'slowly turn' because as your print out points out.....The solenoid circuit is designed to ensure that the armature shaft does not revolve until the drive pinion is fully engaged with the ring gear. Isn't that what I said?



Martin

[bigherb]

So why do they earth the solenoid through the motor?

[CovKid]

Presumably so there is an earth under both conditions. I'd be interested to see what the draw is from the solenoid though. I've never had an issue with a solenoid in 25 years other than where it has actually packed up entirely. The only starting probs I've encountered have been with worn brushes in the motor itself, a flat battery or as I've mentioned, poor main connections from battery to starter - or the (irritating) signal wire dropping off.

Replaced my main connection today with a nice fat chunky cable and it whizzes away now.

[Oldiebut goodie]

I did have the current draw in a note somewhere for our starters but can't find it - I have a feeling it was 12 - 15A with around 20A to start it moving. I'll have another ferret around in my hard drive!

[MidLifeCrisis]

Replaced my main connection today with a nice fat chunky cable and it whizzes away now.

Where did you get the cable/connectors etc for the battery to starter cable?
What cable length did it end up being?
How easy was it to get the old cable out/new cable in?

[California Dreamin]

So why do they earth the solenoid through the motor?

If I had to have a guess I would say that the relatively low amp draw of the 'closing' winding isn't enough to make the armature 'even twitch', given that the starter itself can draw in the region of 150 amps (petrol) and close to 190 amps on a diesel (depending on conditions).

Martin

[CovKid]

Where did you get the cable/connectors etc for the battery to starter cable?
What cable length did it end up being?
How easy was it to get the old cable out/new cable in?

25mm meter tails - sparky stuff. Lots of strands in what I used though - way more surface area than what it replaced. Auto places didn't seem to have what I was after at all and a lot of 25mm stuff only has a few strands in - no good, not flexible enough.

Ring terminals, again electrical wholesaler type places do them I think. Hole in terminals should be 8mm to fit starter nut/stud. Soldered up properly with flux and a mini blowtorch then shrink tubing to seal the ends.

My new cable is actually green/yellow as thats what I ended up with. You can get 25mm in black or red ofcourse.

This sort of stuff. Its not 25mm diameter by the way - more like just under a centimeter.
http://www.ebay.co.uk/itm/Car-Marine-Am ... 3ce1cb3fce" onclick="window.open(this.href);return false; - you'll want the 200amp stuff if its a diesel.

Will measure old cable when I get a chance if you like. I was going to WIKI it anyway next week with all the measurements but it would be based on a right-hand drive with battery behind drivers seat. I merely cable-tied it to existing cable at weekend but once weather is dry I'll pull out the old stuff. You may need to recalculate for other battery positions but the princples will be the same.

Doing a good (and tidy) job on the ring terminals is absolutely essential though (can't emphasise it enough) - was more like plumbers work to be honest.

[Oldiebut goodie]

From the Samba forum - "The 12 volt solenoid current is 11 amps after the solenoid engages, 22 amps before it engages." Just a general post on Vanagons with no reference to diesel/petrol, not that I'd expect much difference between the different starters.

I wasn't far out with what I remembered!

[CovKid]

And only a brief draw at that. The existing cable for the solenoid seems chunky enough for that. I shan't bother with a relay myself (no disrespect). Its just introduces another potential breaking point from my perspective and as I don't have any solenoid issues, its a case of 'if it ain't broke, don't fix it.' - not that it won't work for some.

[MidLifeCrisis]

Will measure old cable when I get a chance if you like. I was going to WIKI it anyway next week with all the measurements but it would be based on a right-hand drive with battery behind drivers seat.

No probs - I can wait for the Wiki!! Thanks for that !

FYI - found this while having a google on starter operation .....

So seems that the motor may rotate slightly (as BigHerb said earlier) while the solenoid engages .... interesting stuff!!

[bigherb]

So why do they earth the solenoid through the motor?

If I had to have a guess I would say that the relatively low amp draw of the 'closing' winding isn't enough to make the armature 'even twitch', given that the starter itself can draw in the region of 150 amps (petrol) and close to 190 amps on a diesel (depending on conditions).

Martin

So you don't know how it works but you say it is wrong.