Curious loss of charge

sdibbers

sdibbers

Well-Known Member
1969 2000TC with 11 AC alternator. All wiring in good condition.

Driving home this evening on the Garden State Parkway. Notice that the fuel and temp gauge starts dropping along with headlamps. Sure enough I start losing power as ignition system losses power too. No charge in the battery, not even enough for the hazards. Funny thing was that the ignition light never came on.

Roll to hard shoulder and wait for a flatbed.

When I get home I put it on charge so I can drive into the garage. Just out of interest I put the voltmeter across the battery terminals and it shows 14.3v at idle.

Question is: Can a faulty battery cause this? In my experience alternators tend to work or not work. Same with the external regulator.

Any ideas folks?
 
PeterZRH said:
If the battery is at fault, usually it won't provide enough current to start.
Click to expand...
I had put it on the charger when I got home.

But my guess is an intermittent fault with either the alternator or regulator. Next step would be an ACR style alternator to replace both the current AC style alt and external regulator.
 
It sounds more alternator related. Usually if a battery if duff, it might start a car straight off the charger. Leave it a couple of days and it won't. But what you are saying sounds familiar. I was driving along and I noticed I had very little oil pressure - the voltage had dropped (thankfully!). The alternator with the external 4TR was failing and it took the battery with it. Changed both (not an ACR but a Lucas A127 which is a more modern version of the ACR).
 
That’s reassuring to read. The alternator on four cylinder cars is a left handed right? I’ll need to find a wiring diagram for the 4TR delete somewhere.

The 127’s are a little thin on the ground here in the states.
 
sdibbers said:
The alternator on four cylinder cars is a left handed right?
Click to expand...

I think you'll find it's right handed.

alternator-mountings.jpg


If all else fails you can change it anyway.
 
I could have spent longer fault finding but the A127 was only £55 new and in any case I wanted the 75A output instead of the 35A of the 11AC as I run an electric fan and when it kicks in previously I got a small voltage drop and the lights dimmed - not any more. Actually as the fan is only 8A in low speed mode that kind of suggests the alternator was pretty weak before it failed. Very happy with that little upgrade. A few people have electric PAS, I'd say for that an upgrade of this sort is pretty much mandatory.
 
Well, I found that Defenders have an A127 so ordered one from a specialist here in the states. @PeterZRH yes, I like the idea of extra capacity.
 
Quick question for those who've already made the change. Did you use the new pulley that came with the A127 or use the original pulley from the 11 AC?
 
I used the pulley fitted on it. You also want to run a second heavy wire to the floor terminal post or to the starter motor/relay.
 
PeterZRH said:
All you need to know is here: Alternator Swap: 11AC to A127
Click to expand...
That's perfect! Thanks.

So, bridge the two large spades on the alternator together and run to positive feed on solenoid. Connect small spade to wire going to the old 3AW unit at alternator end then remove 3AW unit, secure unused negative wire to 3AW and join the two remaining wires together so it now feeds the ign light directly. That sound about right?
 
You don't need to bridge anything at the alternator. The two large spades are the same terminal internally. The connector is common to ACR types. I assume the extra wire was for compatibility with wiring looms and lower output models needed only 1 wire.

And yes, just use the existing wiring for the ignition lamp/feedback circuit and short out where the 3AW was. As you can see you don't need to cut anything. The 3AW bypass wire (mine is yellow in the pics) literally plugs into the 3AW relay base, I removed the 4TR and the rest of the original cable is just tied back out of the way.

What you will need is:

One of these - A127 ACR ALTERNATOR 3 PIN WIRING CONNECTOR PLUG LUCAS/BOSCH + TERMINALS | eBay
And ideally a retainer clip.
 
sdibbers said:
Quick question for those who've already made the change. Did you use the new pulley that came with the A127 or use the original pulley from the 11 AC?
Click to expand...
Hi Steven,
when I replaced the original dynamo on my car with an 18ACR, I was advised to go with the larger diameter pulley and did that. With the larger pully, the alternator is providing sufficient charge at idle speed with considerable electrical load, so all is good. I have not calculated what the speed of the alternator would have been with the small pulley at full RPMs and if that would really have been an issue.
 
DAK said:
Hi Steven,
when I replaced the original dynamo on my car with an 18ACR, I was advised to go with the larger diameter pulley and did that. With the larger pully, the alternator is providing sufficient charge at idle speed with considerable electrical load, so all is good. I have not calculated what the speed of the alternator would have been with the small pulley at full RPMs and if that would really have been an issue.
Click to expand...
that's a good point. Its easy enough to swap if the new one is smaller (thereby spinning too fast)
 
PeterZRH said:
And yes, just use the existing wiring for the ignition lamp/feedback circuit and short out where the 3AW was. As you can see you don't need to cut anything. The 3AW bypass wire (mine is yellow in the pics) literally plugs into the 3AW relay base, I removed the 4TR and the rest of the original cable is just tied back out of the way.
Click to expand...
That's super easy! my 4TR and 3AW are both on the the inner wing, so I'll be glad to clean up the engine bay a little by their removal.
 
PeterZRH said:
Opposite inner wings in my case. 3AW in drivers side, 4TR on passenger side (LHD)
Click to expand...
I am not sure what the stock pully on the A127 alternators looks like but the one that was on the new 18ACR was significantly smaller than the one I used.
 
You must log in or register to reply here.
Back
Top