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TR5/TR250 TR250 question [Not asking for a friend]

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KarlHB

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I hold my hands up and confess my mistake; long story including bad weather, bad temper and little time cut short; I managed to put my new battery the wrong way round, fixed the negative pole to the positive cable, laid the negative cable on the positive pole, went to get a spanner and came back just a few seconds later noticing smoke coming from the alternator. Immediately removed the cable, obviously. Turned the battery around the proper way, cursed a bit, connected it and sat inside the car to try and start it. Noticed smoke inside the car as well. And the car was completely dead.

No lights, no light in the alternator light in the dashboard, but no blown fuses and (hey!) the horn works.

I have replaced the start solenoid and alternator. Is the ignition switch the next thing to suspect? Is there any way of checking this to make sure before I order a new one? Or is there any other culprit part to investigate first?

Alright - I'm ready to take some punches, but also some good advice :smile:

Thanks in advance,
Karl
 
I did that 45 years ago and only melted a wire to the ignition. Also check your fusses. In general, reversing the polarity won't hurt much.
 
Might have fried the ammeter or a connection to it, or one of the wires connected to it. But we can only guess. I think you'll need to get a voltmeter or test light and probe around a bit to find where you are losing power; the source of the problem will then become obvious. I also doubt that there is much damage beyond the alternator and perhaps some wiring. The standard electrical parts, except the alternator, are not polarity-sensitive.
 
+1 on systematic troubleshooting, rather than replacing the entire electrical system.
Ammeter is most likely IMO, but by no means the only possibility.
 
Thank you, guys - for advice and not telling me off :smile: I have ordered a new ignition switch and hopefully that does the trick. The next thing to obtain might then be an ammeter. The weather is such a mess in Norway at the moment, I wouldn't be taking the car for a spin, anyway (I keep telling myself).
 
Don't beat yourself up. I just did the same thing on my tractor even though I looked at the terminals to get it right. Us men and our attention span. Somewhere in moving it into the compartment I got it turned around. I bet you have some beautiful places to drive so I hope you the best.
 
Hello, fellow Triumph enthusiast. Just to keep you posted; I received the new ignition switch, but that didn't solve the issue, either. So, now I have ordered a new ammeter (which will take a loooong time before it reaches me). Good thing autumn is here, with gloomy don't-take-your-TR250-out-for-a-spin-days ;)
 
If ammeter doesn’t fix it, then I’d look at the alternator and the wires to it next. Without turning the car on, that’s the main part that actually saw the negative voltage. The ignition switch should have protected everything else..
 
Power to the lights and ignition doesn't go through the alternator, so it's not likely to be the culprit. You could actually take the alternator off entirely, and the electrical system would work (until the battery ran down).
 
KarlHB said:
Thank you, guys - for advice and not telling me off :smile:
Click to expand...

Well, I just dropped a container with about a gallon of dilute hydrochloric acid on the garage floor this morning, so I'm in no position to criticize anyone...
 
TR3driver said:
Power to the lights and ignition doesn't go through the alternator, so it's not likely to be the culprit. You could actually take the alternator off entirely, and the electrical system would work (until the battery ran down).
Click to expand...

And the lights don’t see any current when nothing was switched on. I think it’ll be a wire that fried. The alt is the only thing I can think of that could absorb the reverse current when everything else was turned off...the only item that actually had a “loop” and no fuse.

The ammeter would only blow after reverse polarity if there was excessive current flow. The question becomes, “where was the current able to flow with nothing switched on?” My money is the alternator and it’s associated wiring. All it would take is a bad diode. As I work through it...I guess it could be the voltage regulator...is that integral or separate on the 250?
 
Reverse voltage guarantees heavy current flow through the main alternator diodes; they form a fairly direct short with reverse voltage applied. Offhand, I can't think of anything else on a stock TR250 that would care, let alone draw too much current because of reverse voltage. Lights, heater, ignition, wipers etc would just go on working (if turned on, which they apparently weren't).

So there's a good chance the alternator is fried as well. My point was just that having the alternator fried would not stop lights and ignition from working.

Could well be a fried wire, but the fault current would also flow through the ammeter (it being between the alternator and battery) and it has smaller diameter wire inside it. Essentially forms a fusible link to the harness wires around it.

On a TR250 (according to several diagrams I checked), the horns get power before the ammeter. So a blown ammeter would disable everything except the horns. Seems like an exact fit to the symptoms described.
 
Not to beat up on the most obvious question HAVE YOU TURNED IN THE LOSS TO YOUR INS CARRIER?
It is a covered loss.....
Mad dog
 
mctriumph said:
Not to beat up on the most obvious question HAVE YOU TURNED IN THE LOSS TO YOUR INS CARRIER?
It is a covered loss.....
Mad dog
Click to expand...

Thanks for the advice - I might do that, although my excess is $450, and I am still not there yet with my expenses due to my mistake.
 
Long shot here, but could have the battery itself internally shorted and broke contact inside causing totally failure.
 
Batteries can certainly fail in interesting ways, but he said the horns still work. If the battery can supply enough juice to run the horns, I would expect at least something from the lights.

A short inside the battery is very rare, which is good because the likely result would be an explosion.
 
Hi, folks. Thank you for all the input. The reason for the car not starting etc. was the ammeter. I became impatient waiting for a new ammeter, so I disconnected the wires to the meter and joined them. Voilá - except now the wipers are on all the time. I'll try and figure out that one after installing the new ammeter when that arrives - at least I have been able do drive the car again :smile:
 
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