Amp gauge shows high reading

[POP]

On my 1968 S 1.5 OTS, I have just finished a cylinder head overhaul, and on restart had to jump start a dead battery. It started but the red ignition light stayed on regardless of revs.

I had a spare 4TR alternator regulator I bought from SNG several years ago but never used - so swapped it over. The red ignition light went out but the Amp gauge was reading very high, and with revs increased to 1500, went off the dial. I have just bought a new battery so that’s ok. Any ideas please?

many thanks Pop

[cactusman]

4TR has failed or is dead and is not regulating. Buy a new regulator. Sadly the original units are not known for their reliability. Left as is you will rapidly severely overcharge and wreck the battery.

[christopher storey]

Before you do anything check your battery voltage with the ignition off. If it is significantly less than 13 volts, say 12.7 or lower , then with a properly working regulator you will see a heavy charge for the first 15 minutes or so . If you measure the charging voltage under such conditions, i.e. with a partially discharged battery , it should be in the vicinity of 14 to 14.7 volts

A new battery is no guarantee that it will be fully charged - indeed AFAIK most batteries are sent out with about 60% capacity charge - so what you have seen is not unexpected provided the parameters I have suggested above are met

[POP]

Thanks for your suggestions. I will be checking with a multimeter tomorrow but in the meantime have ordered a 4TR as a spare if nothing else.

I have read that a blown diode could also give this type of reading. As i jumped the car using an AC charger/started is there a risk i have blown them? Can i check this ?

Thanks Pop

[POP]

Many thanks Christopher and Cactusman. You were both spot on with your suggestions.

I tested the battery before start up this morning and had a reading of 12.8V. I started the car and at 1000rpm had a reading of 17V + and the needle almost off the gauge.

The new 4TR regulator arrived this morning and i fitted this and retested. The reading with rpm at 1000 to 1500 was 14.4V. Also the Amp gauge was reading normal; ie in the plus side but the needle about mid way and not going off the gauge.

So many thanks guys.

All the best Pop

[cactusman]

Glad you got it fixed