Datsun Roadster Forum-311s.org

Anyone else using a circuit breaker on their alternator? Nissanman mentioned it here
viewtopic.php?f=3&t=28837&p=289678&hili ... er#p289678
I was going to use a fuse, but there are some breakers with resets to consider. Would the heat on the driver side with a stock mount affect a breaker?

Linda

Linda, I have the GM conversion on mine and I put a 40 A breaker in the line to the battery. I love breakers but found a flaw. If for some reason my battery was low, like it hadn't been started in a while and took a lot of cranking to get it going, when it did start the alt would put out more than 40A to charge the system popping the breaker. Then I would have to stop put a charger on and charge the battery then restart the car and reset the breaker and all would be good. UGH
I rewired the alt directly to the battery and put the breaker in the line from the starter to the ammeter. That seemed to fix that problem. I also think having a breaker on the hot side of the motor may have some effect but someone with more knowledge on that will have to chime in.

Mike

I did read some comments about the newer breakers, esp off brands, popping in heat or in wide open running. So a name brand like Bussmann or Cole Hersee at least. Did you have a name brand breaker?
Linda

So it depends on what and how you want to protect.

http://www.kendo-usa.org/datsun/datsun_ ... out_68.pdf

Placing a fuse between the starter and ammeter can protect most of the car. However depending on where the problem occurs you still might wind up with the ammeter acting as a fuse first. I would guess that so long as it takes more than 30 amps to fry the ammeter then the fuse will do its job.

The alternator is known to cause a problem with the plastic insulator on the bat post cracking and shorting out. Seems if you want more complete protection you put in two fuses.

You mean a fuse on the white wire before the plug on the starter harness or after? Or is it a black wire, have to check...
Then on the alternator, a fuse on the white wire from the B(at) post? That is where I had a fuse before.
Is there a source for those alternator insulators? Might be good to replace them periodically.
I don’t really want to cut any wires if I can help it so was thinking about the breaker.
Linda

I'd just use the breaker on the alternator. I have made a short harness to go in between the starter harness and the dash harness with a fuse in it.

A fusable link ,is best a high amp circuit breakr could still smoke small med sixe wire
A circuit breaker does not always blow in the slow blow condition...ive smoked a few CBs with slow B problems

I made this.

You know I was thinking of asking if that is possible to do, put the fuse between the connectors, and voila, you made one!
I think I might like one of those, please
A breaker at the alternator hopefully can finish the job.
The thing about fusible links is that they are a bit of a hassle to repair.
I see that they have a kind of circuit breaker fuse now too, not sure how good those are.
Protecting wiring and ammeter though is essential
Thanks for info
Linda

It will be a while until I can make one, hand in cast from surgery. Carpal tunnel and tendon repair.

Ouch. Get better soon.
Linda

Car stereo shops or marine parts dealers would be a good source better quality for 12 volt breakers, Ebay/Amazon unbranded stuff can be sketchy.
Good info here on links http://www.madelectrical.com/catalog/fusible-link.shtml

I had read a fusible link was slower than a fuse to blow, not sure if true. Seems like a good protection idea,though not as convenient. I have a Bussman breaker I added for the time being, Hope their quality is good, but would agree that marine quality is best. Maybe something like this, which looks like a Bussman/ BLue Sea collaboration
https://www.ebay.com/itm/Bussman-187-Se ... %7Ciid%3A1

Linda