Ignition switch testing help

[davehaynes1]

Hi guys.
I posted yesterday about a suspected faulty starter motor..
I've had the starter out and cleaned everything up and all seems to be working well.
Bench tests well everytime.
And at a price of $2200 for a new starter motor I'm going to look elsewhere for the problem.
My suspicion now lies with the IGN switch or a bad battery.

I have a multimeter and I'm going to try and rule out the IGN switch today.

Could anybody please help me with what pins I should be testing continuity across?

Thanks

 

[hydrocarbonPrimate]

At a guess
Acc is accessory so will be first position, IG would be 2nd ignition position,
and ST1 1&2 would be closed on final turn of ignition barrel to activate starter solenoid, but go open when key springs back to 2nd position (after start).

 

[davehaynes1]

( IGN off) 12v to AM1 & AM2
( IGN on ) 12v to AM1, AM2, ACC, IG1 IG2
( START ) AM1, AM2, ACC, IG1 IG2 drop to 8v - 10v ST1 & ST2 have 4v - 6v

All looks good to me. I think?
But unless I can test it when the starter is playing up, I'm wasting my time aren't I?
And I have no idea how to replicate the starter problem

 

[hydrocarbonPrimate]

Genrally in automotive systems the battery voltage shouldnt drop below about 11v when cranking, if it is you have a duff battery or high resistance earth. You want to measure the resistance across the ignition switch which the power disconnected, it will give you an idea of the condition of the contacts, they can, and do build up with carbon and gunk and can be intermittant.

You mentioned tapping the starter solenoid and it working, so is that not prime suspect? Did you clean the brushes and commutator? Are the contacts in the magnetic switch / plunger ok? It's often the case that the plunger will act as a big relay to switch the starting current to the motor and throw out the pinion gear at the same time. You can use jump leads or boost pack to check the opperation of a starter directly.

 

[davehaynes1]

Right, good to know.
Starter was the prime suspect however the starter I have doesn't have the solenoid ontop top like most starters do, so the part I gave a tap to was actually the electric motor.
I cleaned up the brushes and communicator but forgot to dry lube the magnetic switch plunger so I'm gonna whip it back off tonight, dry lube the plunger and check the contacts either side of the plunger.

Can you give me a run down on checking resistance on the IGN switch please.
Pretend you're explaining to a 10 yr old

 

[mainline]

Right, good to know.
Starter was the prime suspect however the starter I have doesn't have the solenoid ontop top like most starters do, so the part I gave a tap to was actually the electric motor.
I cleaned up the brushes and communicator but forgot to dry lube the magnetic switch plunger so I'm gonna whip it back off tonight, dry lube the plunger and check the contacts either side of the plunger.

Can you give me a run down on checking resistance on the IGN switch please.
Pretend you're explaining to a 10 yr old

You could just use a voltmeter or lamp type tester to check that there is a supply from the ignition switch to the starter.

You could purchase a cheap power probe so that you could easily check the switch and or starter.

Car Power Electrical Circuit Tester 9-30V Circuit System Diagnostic Tester Light | eBay

The AUTOOL Power Circuit Probe Tester is a tool designed for the repair and diagnosis of automotive electrical circuits and is quick for troubleshooting. BT210 has the characteristics of simple operation, portability, and various functions.

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[brianmoooore]

Try connecting a piece of wire directly to the starter motor control terminal, as well as any wires that are already connected there. Connect the other end of this wire to a 12 volt lamp inside the cabin, with the second wire to the lamp to the engine block.
This lamp should light every time the starter is operated.
If the starter fails to work, and the lamp illuminates, then it's likely it's a motor fault.
If the lamp doesn't light, try applying 12 volts to the wire and see if the starter works.
What vehicle has a 2200 dollar starter motor?