The Triumph Dolomite Club - Discussion Forum

due to a dodgy amplifier in my car I went to use it yesterday morning and the battery was flat. ok, another job on the list. however, when my girlfriend saw me struggling with the heavy charger/starter she came and helped. she said she'd wanted to help work on the car before so as I got the fat extension lead she connected the leads up wrong! after I rectified the problem I notice that the temperature reads 3/4 rather than the 1/2 way it did before. the fuel gauge works fine as it was empty then this morning I put £60 in it and it now reads full. could this just be an overheating issue coincidently at the same time?

Sounds very much like the instrument voltage stabiliser has popped.

Hope the same isn't true of the alternator diodes...

Should read 10 V on a cheap multimeter and you may even see it pulse...

Electronic ones are available cheap on ebay and from the club.

Jonners

Yeah, I'd be more worried about the alternator diodes than the voltage stabilizer.

how can I check the alternator diodes? will it be charging to high? when I check the voltage stabiliser, do I just unplug the line out and expect 10volts?
cheers chaps

Just check the charging rate and as long as the ign light works as normal and its charging ok youre good to go.
On the stabilizer yes output should be around 10v (easier to read with an older type analogue meter as digi ones are fluctuating so quick.

Tony

With the engine running, you should be getting about 14 volts across the battery terminals if the alternator's working.

Check the voltage when you first start up.

You can get a problem where charging does not start until you have revved the engine (I think that it's above 3000).

The original voltage stabiliser is a bi-metallic thermal unit. It should not matter which way round the voltage is made to get it to operate. And the same with the fuel gauge and water temp; gauge. These are thermo-units as well. So reverse polarity should make no difference. But if you have a modern semiconductor voltage regulator replacement, then that will be damaged . You can check the output voltage with a DVM but it must have a True RMS voltage setting. You should see close to 10 V. Was the ignition switched on when the leads were connected in the reverse polarity ?
If not then a modern regulator will be O.K.
If so any electronic ignition system may be damaged as will any stereo unit.
But yes, as Dave says the main diodes in the alternator will probably be dead / degraded. Does the dashboard voltmeter give its usual reading with the headlights/ heater motor/ HRW / wipers all on at the same time. You may be lucky and get away with it depending on the source resistance behind the reversed leads.
Tony.