Ammeter to Voltmeter Conversion -- Existing Wire Question

[Dave6T4]

View attachment 1173730 Go to Mad Electrical and look at the article on eliminating your ammeter so you don't burn down the dash.
I also purchased the headlight relay kit from Crackedback so I could take the load off of the system.

My friend has a '62 Max Wedge Dart clone. He put a higher amp alternator in it and upgraded the charge circuit wiring gauge as suggested. The car is wired as per this diagram, with the ammeter bypassed. The charge wire between the alternator and starter is new 8 ga. with a 30 amp fuse in fuse holder instead of fusible link. On firing the car up, this fuse blows, and car runs only on battery power. Should this charge wire be fused at all? Is he running too low amp fuse, or is there a problem somewhere else? I know we have all been down this rabbit hole before.

 

[hunt2elk]

My friend has a '62 Max Wedge Dart clone. He put a higher amp alternator in it and upgraded the charge circuit wiring gauge as suggested. The car is wired as per this diagram, with the ammeter bypassed. The charge wire between the alternator and starter is new 8 ga. with a 30 amp fuse in fuse holder instead of fusible link. On firing the car up, this fuse blows, and car runs only on battery power. Should this charge wire be fused at all? Is he running too low amp fuse, or is there a problem somewhere else? I know we have all been down this rabbit hole before.

Mark at Mad Electrical is now recommending to not fuse the wire from the alt to relay, but instead put the fuse in the small red wire on the positive battery harness. Says he hasn't had time to update his website (probably because he spends way to much time talking). I've done my last 2 cars that way. Is it a slow blow fuse your buddy is using?

 

[RJRENTON]

Mark at Mad Electrical is now recommending to not fuse the wire from the alt to relay, but instead put the fuse in the small red wire on the positive battery harness. Says he hasn't had time to update his website (probably because he spends way to much time talking). I've done my last 2 cars that way. Is it a slow blow fuse your buddy is using?

IMO.....in designing an electrical distribution circuit, the "standard" rule of thumb use to be 135% - 150% of the capacity of the wire in the circuit. Example: #8 AWG wire in free air could handle 50 -60 amps. 150% of 60 amps = ~ 90 amps. This would accomodate any instantaneous surges but open on continuous or short circuit conditions. Personally, I would use 80 amp fuse....but maximum current flow is time vs current algorithm.....or time-current melting curve. But, I'm sure others will dispute this based on ???? Discussions?
BOB RENTON

 

[hunt2elk]

IMO.....in designing an electrical distribution circuit, the "standard" rule of thumb use to be 135% - 150% of the capacity of the wire in the circuit. Example: #8 AWG wire in free air could handle 50 -60 amps. 150% of 60 amps = ~ 90 amps. This would accomodate any instantaneous surges but open on continuous or short circuit conditions. Personally, I would use 80 amp fuse....but maximum current flow is time vs current algorithm.....or time-current melting curve. But, I'm sure others will dispute this based on ???? Discussions?
BOB RENTON

Yes, I agree. From all I have read on the subject it definitely has to be more than a 30 amp fuse.

 

[Dave6T4]

I made up a 10 ga. jumper wire to plug in the fuse holder in the short time.

 

[Dave6T4]

What about blue 3 sq. mm. fusible link wire? What would be ga. rating on that?
I looked it up myself; 12 ga. Should be good; may change to 10 ga. later. This would be 5 sq. mm. (rust colour).

 

[hunt2elk]

A fusible link should be 2 wire sizes smaller than the wire it is protecting. So you would want a #12 fusible link on a #8 wire.

 

[Dave6T4]

So I am good, then. Thanks everybody for your advice. That's what this forum is all about. Specialized knowledge.

 

[Dave6T4]

So, this morning, I installed the jumper wire in the fuse holder and put a 12 ga. fusible link between starter relay and bulkhead connector wire buss. All of a sudden, the voltmeter was reading 14 V. My friend had been complaining that this gauge would never show more than 12 V. We figured that after the inline fuse blew, the voltmeter was reading the battery charge and not the alternator output. Basically my friend has been going to shows this summer on his battery! He always put it on a trickle charger after each use, because he was concerned about the 12 V. reading. We are going to replace the fuse jumper with a new charge wire, as everything seems to work OK now. I rode with him this summer to MoparFest in New Hamburg, Ontario, about a 160 mile round trip. All on the battery. Group 27 Wal-Mart piece.

 

[RJRENTON]

So, this morning, I installed the jumper wire in the fuse holder and put a 12 ga. fusible link between starter relay and bulkhead connector wire buss. All of a sudden, the voltmeter was reading 14 V. My friend had been complaining that this gauge would never show more than 12 V. We figured that after the inline fuse blew, the voltmeter was reading the battery charge and not the alternator output. Basically my friend has been going to shows this summer on his battery! He always put it on a trickle charger after each use, because he was concerned about the 12 V. reading. We are going to replace the fuse jumper with a new charge wire, as everything seems to work OK now.

Sounds like you have everything covered and the system is working as intended......excellent!
BOB RENTON

 

[Dave6T4]

Sounds like you have everything covered and the system is working as intended......excellent!
BOB RENTON

Yeah, this was a nice primer for when I get my '64 Polara on the road. At my friend's expense.