Key turned off, engine shuts down but light still on

Post by **mrsnak** » Sat Jul 26, 2008 12:00 am

Finally got to drive my '61 for a good while the other day for the first time!

My mechanic friend noticed while he was working on it that when you turned the key off, the engine stopped but the red light stayed on. He found that pulling the starter button to briefly engage the starter seemed to turn the light off.

I know find that this trick no longer works. I'm assuming a connection is staying open somewhere, and might need some contact spray or replacement.

Any ideas what switch or part might be causing this?

TIA

Post by **alex_holden** » Sat Jul 26, 2008 7:18 am

Try cleaning the contacts in the regulator box (the black thing on the top left as you look under the bonnet).

Post by **mrsnak** » Sat Jul 26, 2008 4:47 pm

Thanks, will report back later

Post by **bmcecosse** » Sat Jul 26, 2008 8:06 pm

Yes - if you have a dynamo the regulator is almost certainly jammed closed and is back feeding the dynamo trying to run it as a motor! It will soon flatten the battery and possibly burn out the dynamo too. Don't leave it with the light on - take a battery terminal off quick!
If it's an alternator - then it has failed in some way (but quite unusually) - again don't leave it ON - isolate the battery or the alternator.

Post by **DAVIDMCCULLOUGH** » Sat Jul 26, 2008 11:30 pm

Yes would agree with BMC, if its still a dynamo disconnect quickly. I saw a newly restored 2 door melt all the insulation off the wiring from the dynamo. Luckily the owner was in the car and the points in the regulator were able to be opened to stop it doing any more damage.

Post by **mrsnak** » Sun Jul 27, 2008 3:54 am

You guys are great.
Yes, had disconnected the battery immediately when I could not get light off. Problem seems to have been dirty contacts in the regulator. Unclipped cap and used fine sandpaper, then contact cleaner on the points. All seems to be good now.

Post by **bmcecosse** » Sun Jul 27, 2008 7:33 am

Well done - good result.

Post by **mrsnak** » Mon Sep 15, 2008 1:43 am

Reoccurred...

Red light is staying on unless I hit the starter motor lightly a couple times.
Cleaned the points and lubricated the whole assembly with contact cleaner.
Right side seemed sticky, but left side was the one I originally cleaned.

Any thoughts? No dynamo, alternator (Datsun motor and tranny)

Post by **MoggyTech** » Mon Sep 15, 2008 2:18 am

If you have an alternator you should not have a regulator box wired up! The wiring gets modified when you fit an alternator.

Post by **mrsnak** » Mon Sep 15, 2008 3:00 am

MoggyTech wrote:If you have an alternator you should not have a regulator box wired up! The wiring gets modified when you fit an alternator.

This has worked fine for a number of years. Car has been fitted as is for at least 10 years with the Datsun drive train. I'm assuming whoever did the mod took this into consideration. Can you give me specifics as to why it would not work now?

Post by **bmcecosse** » Mon Sep 15, 2008 9:39 am

The alternator has it's own controls built in - the Regulator box MUST NOT be used with an alternator! But it's likely it is just there now as a handy connection point for the various other wires, and is not actually doing anything. Although worryingly I see that all the connections do have wires attached! It's probably the alternator that has failed - some of the diodes are likely past their best. Note if the light stays on it is draining the battery, so either disconnect the battery each time, or find the cause!

Post by **MoggyTech** » Mon Sep 15, 2008 12:43 pm

Post by **bmcecosse** » Mon Sep 15, 2008 2:27 pm

Well done MT - that's exactly it. Wish I could draw like that. We can only hope that although the D and F wires are still connected at the regulator box - they have been isolated elsewhere!

Post by **mrsnak** » Mon Sep 15, 2008 4:46 pm

Will look into this this week!
Any idea why it's been fine until this point?
Makes me think that the wires were already isolated even though still connected at the box.
Now have a working aftermarket gauge for the charging system and alternator is currently (no pun intended) charging just fine (14 amps).

Post by **bmcecosse** » Mon Sep 15, 2008 4:58 pm

Hmm - is the gauge in the alternator supply line ? Most would put it in the battery line - so it will show charge/discharge as the current flows in/out the battery. If it's showing a steady 14 amps all the time - that seems very high and will soon fry the battery!

Post by **PSL184** » Mon Sep 15, 2008 5:02 pm

Just a thought - should this read 14 Volts? That would be about the correct reading on a voltmeter but if it is an ammeter then I would expect the battery to explode very quickly ??

Post by **MoggyTech** » Mon Sep 15, 2008 5:16 pm

If it is an ammeter and it's showing 14 AMPS this suggests that the battery or alternator are faulty, or battery is in a very low state of charge.

Some figures for you. Alternator charge VOLTAGE should be between 13.8 and 14.5 volts at engine speed of 1000 RPM or higher.

Alternator charge current, should vary, depending on state of battery, and loads under use, like headlights etc. when battery is healthy, an ammeter should show very little alternator output after a few minutes running, with just ignition loads.

I would proceed as follows. Have battery load tested by a garage to see if a cell is failing under load, or if the battery is just aged beyond it's intended use (about 5 years).

Alternators can be either machine sensing, or battery sensing, and if battery sensing, and the battery is faulty, the charge light may not go out.

It is possible the regulator box is just 'dummy wired' to keep an original look in the engine bay, but I would have that checked just to make sure.

Dynamos are quite happy to see an open circuit when the regulator fails, but alternators get fried as they try to produce as much as 400Volts if nothing is connected to them.

Post by **mrsnak** » Mon Sep 15, 2008 5:27 pm

Sorry, not amps, volts. Idle is around 12. Just disconnected those wires.
Now no ignition light, so can't tell if problem solved or not. Battery is brand new -just replaced.
Like i mentioned before, when I originally cleaned the contacts on the left side regulator, it solved the light staying on problem. Yesterday was when i saw that it was staying on again, but would go off if I tapped the starter switch a couple times.

Post by **MoggyTech** » Mon Sep 15, 2008 5:32 pm

Sounds like you have a very strange setup between alternator and regulator. I suppose it is possible, you have an early alternator that works through the old regulator, but it is highly unlikely.

Does the alternator have a number on it anywhere?

Really though, if you follow my circuit diagram it should fix the problem once and for all, or at least tell you if the alternator is goosed.

Oh, just a thought, check the IGN warning light isn't shorting to the speedo head at any point. That does cause this problem as well.

Post by **mrsnak** » Wed Sep 17, 2008 1:32 am

bmcecosse wrote:Hmm - is the gauge in the alternator supply line ? Most would put it in the battery line - so it will show charge/discharge as the current flows in/out the battery. If it's showing a steady 14 amps all the time - that seems very high and will soon fry the battery!

Gauge was hooked up properly (I think) and it runs about 12 volts, not 14. It is on the battery line.
Would be nice to have the Morris ignition light, but not really necessary at this point.

Car is fine now that I disconnected those wires.

I bow to you guys

Morris Minor Owners Club

Key turned off, engine shuts down but light still on

Key turned off, engine shuts down but light still on

Problem returning...