Starter Switch Replacement

[parkview094]

Hi All,

I had trouble starting the car over the weekend from the pull switch, so popped the bonnet and used the button on the starter switch. It was very stiff to depress requiring much more force than usual. I sprayed liberally with WD40 before giving the button a few more pushes to try and loosen it up, but to no effect. Then it caught fire. Specifically, there was smoke and arc'ing on the starter switch connector where the battery + lead connects. Obviously the starter switch needs replacing, but I can't think of any reason a failure of the switch would cause arc'ing to the extent enough that heat was generated to ignite the cable sheathing? Ignition was off at the time, so I can only assume some + to ground fault within the switch it's-self? Has anyone experienced this before?

..and on the subject of replacing the starter switch. Any hints / tips for how to get access to the other side on an MM? I've not spent any time properly yet as I'm waiting for the new switch to arrive, but I removed the instrument cluster and felt along the cable from the pull switch. Annoyingly it appears to go through some sound deadening material, so I've not been able to see or feel the retaining not on the back of the switch. Shining a torch in through where the instrument cluster fascia is, there really is no clue as to where the switch is fixed. Do I need to take the ashtray/fascia assembly out to get access, or is there some position I should contort myself in to gain access?

[simmitc]

The starter circuit is heavy current and not switched by the ignition, it is always live - you can turn the engine over without having the ignition switched on. Any faulty contact will create high resistance and thus heat with the possibility of melting insulation. Make sure that you disconnect the battery before working on the switch.

I've not chnaged this switch on an MM, but the same design on later cars has a bracket to brace the cable and a short tube with grub screws to join the pull cable to the switch. If you have a look in the parts book then it becomes much clearer what you're looking for.

[oliver90owner]

It may be obvious to you (that the switch needs replacing), but not 100% to me.

Firstly, it may have just been more resistance in the connection than the starter motor, and secondly, is the starter motor bendix jammed in mesh? That may well cause more overheating because of the effective dead short through its windings. Do check out all the possibilities before jumping to the conclusion of needing a new switch. You may well be right, but worth confirming that it is the contactor at fault, first.

[parkview094]

It may be obvious to you (that the switch needs replacing), but not 100% to me.

Firstly, it may have just been more resistance in the connection than the starter motor, and secondly, is the starter motor bendix jammed in mesh?

Not certain it's the switch that needs replacing, but the push button offered much more resistance than I ever recall needing in the past?

Also - the overheating/mini-fire started with the car just sitting (not when trying to start it).. I wonder if the starter switch may have been engaged close-enough to cause a small current to pass to the starter motor, but not enough to turn it?

I don't believe the starter motor is at fault (maybe naively) - because it did start 'on the button' when sufficient force was applied to aforementioned button? is that false logic?

[alanworland]

I had occasion to 'adjust' the cable on my switch as it would only make contact right at the end of the pull range and I remember it being 'fun'!
The switch itself is held in position by a single nut but it's not particularly accessible.
Have swear box at the ready.

Alan

[parkview094]

Is it easier to get access if I remove the chrome center section (with ash tray etc) from the dash first do you think? I've not looked yet, but is it obvious what holds that center section in place?

[IslipMinor]

First of all what year is your Minor? From your description it sounds like pre-1964, with the 'pull' type starter switch, rather than the 'twist key'? If by 'remove the centre chrome centre section' you mean the speedo, that does not help very much, as the starter pull cable and switch is on the RH side of the car.

There might be some adjustment that can be made, but if the starter switch does not work very easily when pressed from the engine compartment, it does sound like the switch needs to be replaced. I had the same symptoms on ours a few years ago, and a new switch solved the problem - shouldn't complain, the original had lasted around 50 years!

You can get at it from under the dash, but it is easier if you remove the RH (driver's) side glove box lid and liner. That way you can see how it all goes together, and also an opportunity to replace the liner if it is in a 'well aged' condition?

The 2 pictures below show the pull cable and the starter switch:

Starter Pull Cable.jpg (54.24 KiB) Viewed 2224 times

Starter Switch.jpg (88 KiB) Viewed 2224 times

To replace the starter switch, first DISCONNECT the battery!

Either note what they are and/or take a picture first of all the cables connected to the starter switch (14), THEN disconnect all the cables. When first built, there were 2 heavy starter cables, one each side of the switch, and one brown cable, connected to the battery side of the switch. Over the years others may have been added.

Undo the front screw on the connector (23) enough to release the switch, undo the nut securing the switch so that it can slide off the switch and pull the switch out from the engine side of the bulkhead. The pull cable and the switch securing bracket (4) do not need to be removed, but it is easier to have a second pair of hands to refit the switch back through the bulkhead and securing bracket.

The connector (23) should be refitted so that there is a hint of slack in the pull cable.

[myoldjalopy]

I think the OP is talking about an MM model - he mentions 'MM' and a 'chrome center section (with ash tray etc)'. This arrangement is different to the later models with a central speedo. If that is the case, there is no RH glove box lid and liner - that area contains the speedo, petrol gauge and oil pressure gauge, right in front of the steering wheel..........

[parkview094]

Thank you, the diagrams are very helpful. How do you get at screw (23) - does that have to be reached through/under the dash, or will it all pull out into the engine bay?

Indeed - I have a '53 MM. I've removed the instrument panel from behind the steering wheel, but there is no sign of the the back of the starter switch.



Will have a better look with a better torch, but it's all mostly hidden by what I presume is sound deadening material.

[IslipMinor]

Yes, under the dash. If you reach up and find the pull cable and follow it down towards the bulkhead, you will come to the end of the bracket (4), just beyond that is the 2 screw connector where you need to undo, but not remove, the screw nearest to the bulkhead. Assuming that the early SII is the same as the later SII and M1000, on the other side of the connector is the nut that secures the switch itself.

[parkview094]

Thanks all for your help! Took the parcel shelf and the heater out and had good access to the cable and retaining nut. Removing the speedo instument panel flooded the area with light so wasn't a difficult job at all.

Of course, despite paying extra for a new 'Lucas' start switch - the new switch was faulty. Removed and refitted the old switch in the end which seemed to be working absolutely fine. Looks like the starter cable can get jammed if twisted, so my only guess is that's what happened previously. One of life's little mysteries. Still - it's given me a good opportunity to remove the heater at least so I can disassemble that to figure out why it's stopped working (suspect brushes).