Discuss Issues with old-school sixties system in the Auto Electrician Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

Hoping someone can advise on this - driving my classic today, 2 years after rebuild including complete rewire and has done 4,000 miles with no trouble. The car has a typical sixties oil-filled coil, distributor, points replaced with aftermarket module, new AGM battery, new leads everywhere etc. No ECUs or computers in sight.
Today, with no warning the engine stopped instantly, as if the key had been turned off, and the ignition warning light came on. I managed to pull over somewhere safe, turned the key off and back on and it fired up and I continued. 2-3 minutes later, it did it again. This time I had a look but couldn't see a problem. The king lead, HT from coil to centre of distributor cap, is not a great fit so I pulled it out and carefully refitted it properly. I then drove home, 120 miles, with no problem. However once going again, I noticed that the ammeter (yes, it's early sixties) was now showing +15A once the engine was above idle for the whole journey. If left to idle it dropped to -15A. Prior to the stopping incident, it pretty much stayed at zero all the time except for immediately after starting for a short while.
Can anyone suggest what I should check? The dynamo has been replaced by a Dynator, which is an alternator that looks like a dynamo. Do I now have a damaged alternator, or maybe a failed battery (Exide AGM, much less risk of corrosion to the battery mountings)? I'm pretty sure it shouldn't be showing 15A charge all the time I'm running above idle.
As you can tell, my knowledge of electrics is close to zero so any help would be very much appreciated!
Thanks,
Roger
 
Aico Carbon Monoxide Detectors
This official sponsor may provide discounts for members

ruston

-
Mentor
Arms
Esteemed
Advent Win
You may of discharged an already low battery cranking to restart , it could take awhile to top up again depending on the output of the alternator and the power used due to the size of the engine. Other than that you may have a bad cell , unlikely as it seems every thing is newish. You may also have a bad earth that also may have contributed to the engine stopping in the first place.
Out of interest what kind of vehicle is it?
 

telectrix

-
Mentor
Arms
Esteemed
50181
without the flux capacitor, it's dead.
 
  • Thread Starter Thread Starter
  • #4
You may of discharged an already low battery cranking to restart , it could take awhile to top up again depending on the output of the alternator and the power used due to the size of the engine. Other than that you may have a bad cell , unlikely as it seems every thing is newish. You may also have a bad earth that also may have contributed to the engine stopping in the first place.
Out of interest what kind of vehicle is it?
Thanks for the response - much appreciated. After the car stopped, I drove another 120 miles over 2.5 hrs to get home, so I would have thought it should have been topped up by the time I got home. No lights, wipers, stereos etc. on, just driving. It was still showing 15A discharge at idle and 15A charge at anything above about 1000rpm.
I wondered if the king lead coming out of the coil could affect either the alternator or the battery? Don't know much about AGMs.
The car is a '65 AC Cobra, original old American Ford V8, 4 barrel carb, Ford points distributor converted with a Pertronix module, and everything else as standard. Earthing is fine with everything new.
 
  • Thread Starter Thread Starter
  • #7
Originally the car would have had a Lucas C40 dynamo and a Lucas RB106 bobbin regulator, but as it has the Dynator (a modern alternator hidden in a dynamo casing) it has no separate regulator. Whatever controls the charging is presumably internal in the alternator. As I mentioned, I'm no electrician but I wonder if the coil being powered by the LT side but unable to deliver HT due to the lead coming loose could have damaged the charging electronics in the alternator. Or the battery? I don't like coincidences and I think it's unlikely that the coil HT lead came adrift at the same time as either the alternator or the battery developed a fault. I've heard mixed reports of AGM batteries. Would it help if I measured the battery voltage at idle and at 2,000rpm to see if it's an alternator problem? Any point in connecting up a spare battery to see if that makes any difference?
 

telectrix

-
Mentor
Arms
Esteemed
it's a Cobra V8. as long as it growls who cares about the electrics?
 

Strima

-
Arms
Esteemed
Check for loose connections on your charging circuit and wiring loom. Also a loose earth between chassis and engine can cause issues.
 
  • Thread Starter Thread Starter
  • #11
Thanks, I'll have another go over it all. I'm mostly concerned that something's been damaged now and will need replacing. But where to start?
 

telectrix

-
Mentor
Arms
Esteemed
then check all connections, then voltmeter across battery when not running (should be 12V ish) then with engine running 2000rpm should get 14.2V
 
D

Deleted member 26818

Is there a particular type of tester for an AGM battery?
No.
All you are doing is placing a load across the battery and then checking to see if it recovers.
If the voltage doesn’t recover on a fully charged battery, then the battery will fail.
 
Wetroom Store - Network Wetroom Suppliers
This official sponsor may provide discounts for members

Reply to Issues with old-school sixties system in the Auto Electrician Forum area at ElectriciansForums.net

Bulk Workwear - Clothing Suppliers for the Whole Forum Network
This official sponsor may provide discounts for members
Top Bottom