Alternator issues possibly

[Gnasha]

Hi, I have started my GT6 MK3 after a long lay up.

 

Engine runs well even tho the carbs require sorting.

 

Problem:  alternator is not charging the battery.

 

Engine running, I have disconnected the wires at the alternator and I get 18 volts between the large brown terminal and earth.  Reconnected I get 12.46V across the battery terminals.

 

Other symptoms:

 

Ammeter shows negative 1 amp

Fuel gauge reads zero (tank is half full)

Ignition light just manages to glow prior to starting then goes out when engine is running.

 

Engine stopped: Multimeter between the brown termainal and positive terninal on the solenoid shows a connection

 

Battery is new and recharged, after running the engine for about 20 mins the battery requires a full charge which told me somethings wrong in the first place.

 

I have purchased a Voltage stabilizer in anticipation.

 

Any help would be appreciated, thanks for reading this

 

John

 

[Pete Lewis]

glowing warning lamps , low charge rate and connectivity sounds like a  rectifying diode has failed 

 

you can ring them out with a meter , each  should only pass current one way .

[dougbgt6]

ACR alternator rectifier/repair packs are £10 - £15 on ebay, you have to use a soldering iron, but it's not intricate soldering.

 

The fuel gauge may be a different problem, maybe a new voltage stabiliser required, as you  suspect. The fuel gauge and the temperature gauge are both feed from the VS, have you noticed the temp gauge not reading as it used to? If the temperature gauge is OK then it may be the sender in the fuel tank. or the wiring to it.

 

I've recently got rid of my ammeter,  ALL the battery current went through it, the wires got very hot! You might try bypassing the ammeter just in case this is the problem.

[Gnasha]

Thank you for the reply.   I thought the alternator would be ok if it produced 18V, and further thought that the issue was somewhere in the wiring, no?

 

If i see 18v between brown and earth why dont i see it across the battery?

[dave.vitesse]

Please not remove the leads from the alternator and run the engine as this can damage the electronics within the devise.

 

The 18 volts is an open circuit reading with no load connected and is not a very useful figure for fault finding.

 

The correct readings across the battery are with no engine running 12.5 volts. With the engine running at 1500 rpm and greater 14.5 volts.

 

I would first check the wiring between the alternator and the battery and if all is OK then it does look like the alternator's internal regulator may be defective.  

 

Dave

[Gnasha]

Please not remove the leads from the alternator and run the engine as this can damage the electronics within the devise.

 

The 18 volts is an open circuit reading with no load connected and is not a very useful figure for fault finding.

 

The correct readings across the battery are with no engine running 12.5 volts. With the engine running at 1500 rpm and greater 14.5 volts.

 

I would first check the wiring between the alternator and the battery and if all is OK then it does look like the alternator's internal regulator may be defective.  

 

Dave

Thank you Dave 

[Gnasha]

Thanks to you all for the feed back.

 

 

The problem is now resolved, the alternator was not grounded to the engine.

 

Moral of the story is "if you have a problem start with the last thing you did"   I removed the alternator to replace the belt and PAINTED some parts therby isolating the alternator

 

Thanks again.

[dave.vitesse]

Good to hear you solved the problem.

Dave

[dougbgt6]

John, A "Doh" moment, worthy of Homer Simpson.   Well done and well done for for owning up, not sure I would.

[Gnasha]

John, A "Doh" moment, worthy of Homer Simpson.   Well done and well done for for owning up, not sure I would.

I was just so pleased that I had resolved the problem.   so easy to trace, +ve voltmeter on brown connection on alternator,  -ve on body of alternator = 14.4volts reading . connect earth to engine 12.46 volts.  It was as you say a Simpson moment  lmao