• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
  • When posting a classified ad, you MUST select a prefix from the drop-down next to the subject line. If you don't you will get an error and your ad will not be posted!
Tips
Tips

No Charge

Share this page

D

DougF

Guest
Guest
Offline
I'm having a problem with keeping the battery charged, or the TR6 would be more accurate.

The alternator has been to the shop and is working well. The battery is brand new but having the same results as the year old battery that is now going into the TR3. The ammeter is indicating a +12 - 15 at any speed even after a full trickle charge. The only problem is the battery is not getting charged.

Any ideas where to look?
 
Sounds like you must have an electrical "leak" somewhere, that is allowing current to flow all the time. Unfortunately, such things can be very difficult to find.

I would start by trying to get a more accurate idea of how much current you are losing. Try removing a battery cable and connecting a 12v test light between the removed cable and it's battery post. If the light comes on, then it will show you when you've disconnected the leak. If not, you may need to use something more sensitive, like a DVM set to measure DC amps.

Once you've got an indicator of the leak, you can start disconnecting things to try to isolate the problem. Since your 72 won't have an anti-runon solenoid, I would probably start by removing the #2 fuse (with brown and purple wires to it). If that "fixes" the leak, the problem is in the purple circuit somewhere, possibly the glovebox, trunk or interior lights staying on.
 
You may have a "new" bad battery. Baad batteries can act very strangely. Ground cable and charging connections can be bad too but I figured you have checked those things.
 
Thanks Randall. I'll get out the test light and see what I can find.

I was afraid I might have a bad battery, but a brand new one and a year old one are both producing the same results. All of the connections have been cleaned and treated with a product I sell for automotive electricals. Thanks
 
DougF said:
I'm having a problem with keeping the battery charged, or the TR6 would be more accurate.

The alternator has been to the shop and is working well. The battery is brand new but having the same results as the year old battery that is now going into the TR3. The ammeter is indicating a +12 - 15 at any speed even after a full trickle charge. The only problem is the battery is not getting charged.

Any ideas where to look?
Click to expand...

Doug: I had the same problem with the TR250 a few years ago. I traced the problem to the alternator, the original Lucas 15AC. One of the diodes in the 3-phase bridge rectifier was partially shorted and conducting in the reverse direction. This allowed my battery to fully discharge over night. In this case the alternator was able to produce enough charging current to revive the battery and power up any loads without indicating a discharge. However, I had to use by charger/starter to get the engine started, a real pain in the neck. This problem may have been missed by the electric shop.

Try this. Go for a run or use a battery charger and get the battery up to a good level. Now disconnect your alternator. Leave it this way at least over night. After waiting for possible discharge, check the battery voltage. If it hasn't changed, you have a bad diode bridge. These are available for most Lucas and other brand alternators. If the battery voltage is low, you need to continue the diagnostics. Just a matter of elimination. Good luck.
 
How long does a charge hold? Overnight? 3-4 days? I had a similar problem after installing a radio. It seemed the "memory" in the radio (Denon) would drain the battery after 4 days of no driving.
 
angelfj said:
DougF said:
I'm having a problem with keeping the battery charged, or the TR6 would be more accurate.

The alternator has been to the shop and is working well. The battery is brand new but having the same results as the year old battery that is now going into the TR3. The ammeter is indicating a +12 - 15 at any speed even after a full trickle charge. The only problem is the battery is not getting charged.

Any ideas where to look?
Click to expand...

Doug: I had the same problem with the TR250 a few years ago. I traced the problem to the alternator, the original Lucas 15AC. One of the diodes in the 3-phase bridge rectifier was partially shorted and conducting in the reverse direction. This allowed my battery to fully discharge over night.
Click to expand...

I had the same problem on my '74 TR-6. I could disconnect the single brown wire at the alternator, and it would hold a charge. (You can also do the test mentioned above. If the discharge on the battery goes away when you disconnect the brown wire, it's the source of your problem). I repaired mine with a GM alternator.
 
I don't notice the drain so much while the car sits, but it usually doesn't go long without being run. The stereo has been in it for a few years and hasn't been used all summer since the new engine. The electric fan is the only addition, but things were good for a while before this problem reared it's ugly little head.
I checked for a short with the test light last night and it didn't light. I'll be checking things with the multimeter shortly and am hoping for the best.

Thank you all for you information.
 
DougF said:
I'm having a problem with keeping the battery charged,
Click to expand...

DougF said:
I don't notice the drain so much while the car sits,
Click to expand...

Ok, I am confused. Are you saying the battery runs down while you are driving the car?

Maybe if you describe the specific sequence it would penetrate this foggy old brain better.
 
I guess my explanation was lacking. I'm not noticing the drain while the car sits, but I can't totally rule that out. I will test it shortly. There will be a small drain from the radio clock. I will retest the alternator too.

The ammeter will show a positive reading at initial start up immediately after removing the charger, yet the battery drains and eventually dies if driven far enough. The ammeter acted properly when the car was started without the alternator plugged in.
 
DougF said:
The ammeter will show a positive reading at initial start up immediately after removing the charger, yet the battery drains and eventually dies if driven far enough. The ammeter acted properly when the car was started without the alternator plugged in.
Click to expand...
Ah, that's an entirely different kettle of fish! You can ignore my previous comment about a constant discharge.

I take it the ammeter moves slightly to the discharge side after some period of driving? And it takes quite a bit of driving with the lights off for the engine to actually die?

I had a similar problem on a non-LBC once (but with no ammeter). Eventually traced it to the nut not being tight on the engine ground strap. Apparently it would micro-weld and make contact good enough to start the engine and charge the battery at first, but then heat & vibration would open up the connection and the battery would slowly run down.
 
Just removed, cleaned and tightened down the ground strap and hoped that would be it. Unfortunately, the search continues.

Another bit I noticed, at start up, the ammeter sits at center for a few seconds and then jumps to the positive side at about 15.
 
Did a little digging this evening. Don't know when this happened, but the brown/white wire at the ammeter got a bit hot and was melted for six inches passed the gauge. Might explain the fried rectifier at the alternator, and probably the charging problem.
I'll try patching it together for now, or run to TRF in the morning for a new harness. Don't feel like rewiring the car.
 
DougF said:
or run to TRF in the morning for a new harness.
Click to expand...

Jeez, I feel lucky I can drive 90 miles to Goleta to stop by MOSS.... I'd love to have TRF that close!
 
It's about a 70 mile drive for me...1 1/2 hours.

Hopefully they'll have a harness because the patch job didn't work.
 
A charge after start, even with a charged battery is normal. The regulator will see the lower voltage after the slug of current used to spin the starter. It's the constant charge that's a symptom. Normally the charge should sag back to 0.

I see a few potential (ugh, sorry for the pun) problems in your electrical system.

After a long enough drive, either the regulator gets hot enough to quit, or the brushes are only just touching the slip rings. A short bench test won't show either of these problems.

It could also be that the ammeter has decided not to play anymore.

The burnt wire says loose connection. If the nuts were tight on the back of the meter, then it's possible the connections inside the gauage have come loose.

A fully charged battery is 12.5 volts and above. Check it, then leave it sit over night, disconnected, Then the next morning if it reads less than b12 v., you have a shorted cell. Unlikely in a new battery, but not unheard of.

What is the voltage at the battery when it's running? should be 13.5 with nothing on at idle. I'm wondering if the connection from the alternator to the battery common point is loose or open. The alternator works to keep the interior stuff on, but the battery is running the engine. Those ammeters aren't all that accurate as far as how much, so it is possible that the needle swings 10 amps and it's not actually that much. The fact that the repaired wire at the ammeter didn't fix the problem is what makes me go down this path.

FWIW. :shrug:
 
Just got back from TRF with a new harness and Dan Master's book, new hope and a lot less money.

After wrapping the harness last night, the ammeter read a positive 30 and the car didn't want to idle. I have a different ammeter to swap out and the harness. Might need to change regulators too. Should know by tomorrow.
 
TRF is more like an 80+ mile drive each way.

I pulled my harness and found everything pretty much melded together at the ignition switch. I'm glad I got a new one.

It's definitely going to be more difficult going back in than it was coming out. I cut all of the wires off about two inches from it's connection so there is a colored flag to show me where the new harness goes. Routing the new harness will be very tedious.
 
especially up around the column. oog, take your time and get it where it belongs. I am having a hard time figureing out where there was enough resistance to keep it from burning up completely.

Pics man pics!
 
Back
Top