TR4/4A TR4a electrical conundrum

[richie]

I fancy myself to be quite handy with the multimeter but can't bring myself to figure out the obvious problem with my TR.

I plan on converting to a fully relay based electronics system over the winter but until then I am curious to resolve an electrical gremlin which has crept up again while I was trying to set my timing this afternoon.

The problem is as follows, and is intermittent.

Ignition off.

1- Flip the ignition on, red light goes on.
2- Go to engage the starter and I hear click as the red light goes out.

Sounds like a dead battery so far right? Hang on.

3- Return key back to ON position and red light is no longer on...
4- Switch key to OFF position and start over again (red light goes back on when the cycle is repeated).

In the past, repeating many times usually resolves the issue. however, sometimes it gets stuck and after repeat several times, the red light no longer goes on when the ignition is flipped on. When measuring battery voltage I read 12.4 until the ignition is flipped on where it reads 0.2 (yikes! I know).

Nothing is getting obviously warm, including the positive terminal to starter, solenoid, starter, generator. Etc....

I've disconnected the generator and starter in case something was stuck and creating an short. No luck. I swapped out the starter solenoid earlier this year for this exact reason, problem is back.

Any ideas for those who have been here?

Thank you!!!

 

[sd80mac7204]

Ah yes! You need to paint it purple, place it in a large steel drum, and beat on it with a big stick until the demons come out!

 

[TR3driver]

Sounds very familiar to me.

When you check battery voltage, are you probing right on the tops of the posts? If not, try doing that. If the voltage right at the tops of the posts is going to zero, then you do have a bad battery.

But if you only see zero when probing the battery clamps, then most likely you have a bad connection between clamp and post. Remove the clamps and clean both posts and clamps until the metal is shiny and nearly white, not the dull gray color that you see outside. Also make sure that there is still some space between the 'ears' of the clamp when the pinch bolt is tightened. I like to also remove the pinch bolt from the clamp, so I can make sure that the nut will turn easily down the threads (sometimes corrosion will block the nut from turning, just when it appears to have clamped the battery post firmly).

Note that, if it is a bad battery, it may still test fine on any kind of tester. The battery itself is actually fine, the problem will be a broken conductor inside the battery case. But there is no practical way to repair it, just replace the battery. BTDT

 

[richie]

Interesting....

I too was fist convinced it was the battery and brought it in to be tested under warranty. Their battery tester said it was fine and I came home and it worked right away.

Now my only question is could a bad battery cause it to fail only when loaded, almost acting as if its dead?

 

[Simon TR4a]

I am no good at electrical stuff but if you can I would substitute, one at a time, "known to be good" parts until you solve the problem.
First try a different battery, if that does not help try a different solenoid, then a different starter.

 

[TR3driver]

Now my only question is could a bad battery cause it to fail only when loaded, almost acting as if its dead?

In the case of that broken conductor I described before, yes, certainly. Any vibration or movement (like you taking the battery out) may move the broken ends enough that they make contact through a relatively small area of the break (think jagged peak touching jagged peak). Then as long as those two pieces remain in contact, the battery appears fine. Once the connection is broken through either enough current to melt the tiny area, or by vibration or movement, the battery goes back to being 'bad'.

I've gone through this twice now (although not on a Triumph either time). Once the battery was under warranty and they refused to honor the warranty because their tester said the battery was good. I don't shop there any more. The other time it was an older battery so I just replaced it.

But I have also seen similar symptoms caused by a more-or-less invisible layer of (I assume) lead oxide inside the clamps and on the posts. Whatever the layer is, it doesn't conduct worth a darn. You'd open the door, the dome light would work fine, hit the starter and all goes dark. Turn the key back off and wait, sometimes the dome light would slowly come back on, sometimes it wouldn't. More than once, I've coaxed the engine to start by taking my pocket knife and digging into the post and clamp to create a connection. (Not normally recommended of course, but sometimes it was expedient to get the vehicle started so it could be moved some place warmer to work on.)

My then-future wife thought I was a genius after I got her old Dodge started that way one cold winter morning.

I've even seen sparks coming out of the bad connection!

 

[richie]

Well still not sure what it was, but I went back in, removed the battery, removed the negative terminal, sanded the contact point, reassembled and low and behold it worked. So I'm not sure if it was parasitic losses or a fluky battery but now it starts!

Now, back to the original project of trying to tune these things. That'll be another thread!!!

 

[DanB]

Every time mine has done that it has been corrosion on the battery terminals, or a loose cable. Apparently they are sensitive there. ; )

Dan B

 

[Mickey Richaud]

Every time mine has done that it has been corrosion on the battery terminals, or a loose cable. Apparently they are sensitive there. ; )

Dan B

And if you don't have a good ground strap between the engine block and the frame, it'll play havoc with you as well.

 

[Deleted member 8987]

I have a portable (handheld) 12V load tester. You have a bad battery, that will show it. 10 seconds of holding the load switch and the voltage cannot drop below 9v, I think it is. Marked on the gauge.
Had it for decades, use it still. Doesn't work on six volt batteries, tho.

Oh, and you ARE sure what the problem was. Key on, red light on, turn to start, nothing and light goes away, key off and back on, light on.
Sanding the connection did it, but that's just a stop-gap. Get a reamer.
All parts stores have them, good ones are "T" shaped, reams the cable end to a specific angle, and the battery terminals to a specific angle, for 100% contact.
Wire brush types are no better than sandpaper, and the only thing they are any good for is cleaning out corroded light sockets.

Dave

 

[TR3driver]

I have a portable (handheld) 12V load tester.

FWIW, the folks at O'Reillys have one too, that they will bring out and use on your car for free.

However, a battery with a broken conductor inside may pass the load tester and still not be able to start the engine. The handheld units only test to 100 amps or so, while the starter draws over 500 amps when the solenoid first closes. (It drops rapidly after that, maybe only 300 amps while actually cranking.)

If the difference is enough to open up the contact between the broken ends, the battery will appear to go dead when you hit the key.

I have a portable (but not handheld) unit that goes to 500 amps, but wound up replacing the battery before I got a chance to try the load tester on it.

If you can probe directly on the terminals and see zero volts, the battery is bad (or severely discharged) no matter what any tester tries to tell you. Even with a dead short and the wiring on fire, a healthy battery will still show 6 volts or more directly at the terminals.

 

[Deleted member 8987]

YA-201 Snap-On is 125A draw. Now, having seen the remains of an exploded battery, if I was drawing 125A and an internal connector opened......with the hydrogen generated by a battery....not sure I'd want to be nearby.
That said, the only time I have ever seen loose connectors was on old exposed connector batteries.
Never, as in ever, seen a modern enclosed connector battery with an intermittent.
One thing that WILL break things loose is removing battery cables by twisting them off.
First clue is excessive corrosion on the top, as you first break the seal between the post and the case.
ALWAYS use a puller. I keep several on hand.
Not saying yours did not have an internal break, just never seen an intermittent on internally connected batteries.
Dave

 

[TR3driver]

Good point about the explosion, it is a real risk. I've had a battery explode, although fortunately I was in the house when it happened. (Unfortunately, that car had the hood release cable passing directly over the top of the battery, which made it fun trying to put the fire out without being able to open the hood!) In that case, the explosion was triggered by a spark from a makeshift battery charger that had malfunctioned; but it could have been triggered by anything.

I had what I'm pretty sure was a broken conductor twice now, both times in sealed batteries. Likely they had been abused to some extent, by twisting the clamps or whatever (although one of them was a side terminal battery so no clamps). But I didn't bother cutting them apart to investigate.