More ignition/starter trouble ('72 P5B)

[bogbasic]

Hello, I have had an intermittent problem with starting in which the car starts fine from cold but once the engine is hot,
turning the ignition switch just gives a click. This click emanates from the relay next to the fuse box.

Over the years I have replaced the inhibitor switch and adjusted it several times, I've replaced the wiring to the inhibitor switch, I've replaced the starter motor and the starter motor relay (i.e. the one that is linked to the inhibitor switch).

Anyhow the problem has been getting worse recently and I'm too scared to drive the car in case it gets stuck somewhere!! In fact I've been too scared to go to the petrol station for several years so I have to bring back petrol for the Rover in a jerry can!! Shows aren't my forte.

I thought the engine might be seizing when hot but a test wire shows that there's no current going through the brown and white wire to the starter motor and it only happens when the engine has been run till its hot. It stems from the fact that there's no current going through the red and white wire from the ignition switch when the engine has been run for some time. When its cold, a test light shows that turning the ignition switch sends a bit of current down the red and white wire but none at all when the engine has been run for some time!

What can be going wrong?? Could it be something to do with the ignition switch or the ammeter even?? The circuit diagram shows these two are connected.

I am going to replace the relay next to the fuse box since this is called the relay for the starter motor in the workshop manual (51 on circuit diagram) but it looks more like a relay for
the alternator and a phone call with Jon Wadhams today suggests thats what it is.

Anyhow if someone has the time to look into this, it would be very much appreciated.

[Phil Nottingham]

The relay next to the fusebox is the field isolating relay for the alternator.

There is another one next to the heater box for the inhibitor switch.

I think your problem is just a faulty ignition switch - what model/year is your car?

[bogbasic]

Hello

its a 1972 K-reg with a thief-proof coil system although the coil itself was replaced about 4 years ago. Can the steering-column type of ignition switch be purchased these days or is buying second-hand the best choice?

Cheers

Jon.C.

[Phil Nottingham]

A secondhand one is only available - alternatively fit the console switch of the earlier models as I have done.

Bypass the switch and see if the symptoms disappear

The clicking of the field isolating relay shows its working Ok.

It could also be a poor connection in the Lucas bullet - trace the wiring back

[bogbasic]

Hello, some more testing showed that it is the darned inhibitor switch again. I will try to adjust it with the engine hot this time. Any clues on making it more reliable so I don't have to adjust it every 2 or 3 years (with very low mileage). Also, I plan to wire in a connector to allow a quick temporary bypass of the inhibitor switch to get out of a crisis, but I gather you bypass the inhibitor switch at your peril.

[Phil Nottingham]

Have you tried replacing the switch - I have never had trouble ith it going out adjustment so often?

Yes - its is highy dangerous to by-pass it

[Keith - Portsmouth]

If you do decide to fit an emergency bypass switch, can I suggest that you use a spring loaded switch - one that only makes when you push it, and breaks when you take your finger off. That way you cannot accidentally leave the inhibitor switch bypassed, and it is a conscious action to bypass it.

[bogbasic]

Hello, now its looking like a dodgy bullet connector on the lead from the ignition switch. Clean plastic wire going into nice clean bullet connector, but were they connected? Intermittantly.

[keith]

philnottingham said:

Have you tried replacing the switch - I have never had trouble ith it going out adjustment so often?

Yes - its is highy dangerous to by-pass it

I have often wondered why automatics have inhibitors but not manuals. Why is that?

[bogbasic]

I suppose with a manual you have the clutch to save you if it starts in first gear or reverse.

[stantondavies]

The inhibitor is for safety and to prevent gearbox damage. When starting with a starting handle the inhibitor switch is not effective so it is important to ensure car is in park to avoid a flattened driver.

[bogbasic]

...but I can't even start a morris minor in neutral with the crank, let alone a 3 litre or 3.5 in gear

[Deleted]

Who's got the P5B with a starting handle then?
God bless them!

Ady

[redsunbeam]

For some reason my P5B has another ignition switch in the centre section of the dash next to the rev counter. It bypasses the inhibitor switch. Told it was something to do with being a ministry car.

[DaveCole]

Redsunbeam

Govt. cars did indeed have bypass switches fitted, but they were housed in a Coupe instrument pod along with hazards etc and were toggle switches same as wiper-lights etc.

Our own MOD (59AM19) car does not have bypass fitted, however we do have a MT section technical order telling you how to do it, perhaps if security was an issue.

DC

[Deleted]

I have occasional problems with my started switch. Replacing it with one just as worn doesn't seem to be a great solutio though. Are there any new panel switches available, as in the earlier P5s, or are they only available second hand too?

[Deleted]

The type of ignition / starter switch in the dashboard can be obtained from Holden Classic and Vintage car parts : www.holden.co.uk/

Remember to obtain a matching barrel with keys.
They also show a wiring diagram for the switch..

Cheers

Adrian