2 replies to this topic

[samuel86]

Electrical issue.

 

Holden HJ, carby 355, ice ignition and msd 1 wire 160 amp alternator, Optima yellow top. Electric fuel pump, thermos and power steering.

 

The car was re-wired years ago and only just got the engine in and running. The electrical shop has since closed.

 

Idling in the garage;

- Alternator is charging 13.5-14.5v

- Battery holding charge

- Almost no voltage drop from the front of the car to the back.

 

The car drives for 10-15 minutes but as soon as the revs drop below 600 rpm, the volts drop and the ignition starts to break up, then car stalls. The battery drops below 12v and the car wont start. I can see the volts are steady around 13.5 when +1,000 rpm, and drops a little when under that. 

 

So far, I have done the below with no luck.

- Earthed cable from alternator to the block

- Bought a brand new Optima yellow top battery

- Swapped out the alternator

- I’ve added a light under the dash to keep the alternator excited but it hasn’t helped.

 

Where have I gone wrong? For the life, I can’t figure out what should be so simple.

 

Anyone have any suggestions?

 

Attached Files

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[RallyRed]

What are the loose wires near the steering rack boot? ...or is that an "in progress pic"?
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Idling in the garage;

- Alternator is charging 13.5-14.5v - Do you mean that 13.5 -14v was measured AT the battery terminals?

- Battery holding charge

- Almost no voltage drop from the front of the car to the back.



The car drives for 10-15 minutes but as soon as the revs drop below 600 rpm, the volts drop and the ignition starts to break up, then car stalls. ( sounds like it is running off the alternator, and the battery is not even connected/ is a dud? - but you have replaced it ) The battery drops below 12v ( when you say it drops below 12v....do you mean initially when it is stalled? or when you have been cranking for a while?)..... and the car wont start. I can see the volts are steady around 13.5 ( at the battery?) when +1,000 rpm, and drops a little when under that.

Reckon a cheap clamp on ammeter would be a good tool for you. Then you can SEE that the alt. is actually putting current into the battery to charge it. Likewise, when the engine revs drop below 600, you can also SEE if the battery is contributing to the cars current draw, or just the alt is doing it all. p,s, is 600 rpm low?

Edited by RallyRed, 19 December 2023 - 06:06 PM.

[S pack]

What are the loose wires near the steering rack boot? ...or is that an "in progress pic"?
 

Alternator wiring Col.