Underhood Ammeter Bypass

[1970FuryConv]

Chrysler knew about the "flaw" for years.
That's why all the police pursuit cars had their own H.D. shunt or bypass.
My 73 Satellite wagon has a factory shunt too.
By 1974 when the newly designed Formals came along the wiring was also redesigned and the gauge acts as a voltimeter.
The B bodies for 75 got the redesign and the F bodies in 76.
A bodies trudged along since the F replaced it.

Okay, because my ammeter is frozen in place, so that means its probably a rusted piece in the gauge, so Ill just worry about fixing that then

@cbarge is knowledgeable. By his post, you are repairing a voltmeter. I have no experience with formals, so I can't personally attest. However, 1970 was the last year full current ran thru the ammeter. The proof is in the factory shop manual pics above. Ammeter bypass is unnecessary after 1970. By cbarge post, 1974 and later would be voltmeter bypass. Definitely unnecessary.

 

[77newyorker440]

@cbarge is knowledgeable. By his post, you are repairing a voltmeter. I have no experience with formals, so I can't personally attest. However, 1970 was the last year full current ran thru the ammeter. The proof is in the factory shop manual pics above. Ammeter bypass is unnecessary after 1970. By cbarge post, 1974 and later would be voltmeter bypass. Definitely unnecessary.

Yes, I misread my gauge, it actually says alternator, and I believe @cbarge and am thankful for his insight, just wanted to make sure that I was doing the right thing to my gauge. I'll probably just pull it out soon and free up the needle so it starts working again
Thanks,
77newyorker440

 

[patinated_imperial]

I am just posting to thank cbarge and all contributors in this thread!
Just completed the by-pass on my '66 Imperial. During the process I discovered some sketchy repairs in the original cable harness through the am-meter, but also, that the car has a newer alternator. I don't know if the new alternator has a higher capacity than the original (making the by-pass even more relevant). It is a square back, but labeled #7001 and re-manufactured in Mexico. Searching for that part no. shows a round back? Comments to the capacity welcomed.
Found small signs, that the cable from the ammeter to the starter relay at the bulkhead connector had been hot, but luckily no real damage.
I routed the by-pass in a fibreglass sleeve and across the radiator support instead of over the engine. This was the shorter route as the starter relay is just behind the battery. Fusible links are not common here, so I used a 30Amp fuse, being prepared to have to change it to a larger fuse or source a fusible link.
Trying to post pictures below:

Cable in radiator support:

 

[cbarge]

I am just posting to thank cbarge and all contributors in this thread!
Just completed the by-pass on my '66 Imperial. During the process I discovered some sketchy repairs in the original cable harness through the am-meter, but also, that the car has a newer alternator. I don't know if the new alternator has a higher capacity than the original (making the by-pass even more relevant). It is a square back, but labeled #7001 and re-manufactured in Mexico. Searching for that part no. shows a round back? Comments to the capacity welcomed.
Found small signs, that the cable from the ammeter to the starter relay at the bulkhead connector had been hot, but luckily no real damage.
I routed the by-pass in a fibreglass sleeve and across the radiator support instead of over the engine. This was the shorter route as the starter relay is just behind the battery. Fusible links are not common here, so I used a 30Amp fuse, being prepared to have to change it to a larger fuse or source a fusible link.
Trying to post pictures below:
View attachment 428527
Cable in radiator support:
View attachment 428528View attachment 428529View attachment 428530View attachment 428531

Yer Welcome!!!

 

[Trace 300 Hurst]

I am just posting to thank cbarge and all contributors in this thread!

It appears to me that you like to do things carefully, properly and thoroughly.

 

[67Monaco]

I am just posting to thank cbarge and all contributors in this thread!
Just completed the by-pass on my '66 Imperial. During the process I discovered some sketchy repairs in the original cable harness through the am-meter, but also, that the car has a newer alternator. I don't know if the new alternator has a higher capacity than the original (making the by-pass even more relevant). It is a square back, but labeled #7001 and re-manufactured in Mexico. Searching for that part no. shows a round back? Comments to the capacity welcomed.
Found small signs, that the cable from the ammeter to the starter relay at the bulkhead connector had been hot, but luckily no real damage.
I routed the by-pass in a fibreglass sleeve and across the radiator support instead of over the engine. This was the shorter route as the starter relay is just behind the battery. Fusible links are not common here, so I used a 30Amp fuse, being prepared to have to change it to a larger fuse or source a fusible link.
Trying to post pictures below:
View attachment 428527
Cable in radiator support:
View attachment 428528View attachment 428529View attachment 428530View attachment 428531

Just change it to a circuit breaker.

 

[Gerald Morris]

A 1966 Chrysler or Imperial won't have any alternator greater than 60 amps maximum capacity. I recommend you get a fresh 60 amp alternator if your power harness is wired to handle that much, as I suspect it is. Are the ammeter wire and alternator charging wire in #10 AWG? If so, you have a 60 amp alternator HARNESS, though that squareback MIGHT be able to produce more current than that. Is your ignition transistorized, or do you use old school breaker points? If the latter, then you can safely go back to an original "roundback" alternator if you like.

Main power circuits best work with delayed over-current protection. That's why fusible links were contrived for protecting high demand circuits to start with: they won't interrupt current unless there is a SERIOUS overload. "Slo-blow" fuses and delayed breakers have been developed since the 1960s, as have fusible links which can be placed in a circuit box like a fuse box, but ordering fusible link wire isn't that difficult and you would probably be best served to get some. If you're keeping 60 amp circuits as your largest, then #12 AWG fusible link wire can be purchased in nice 10 foot rolls, like primary wire, which you then can cut lengths from to create your own links!

I realize that such a retrograde solution probably carries a stiff tariff in Denmark, so again, buy in some bulk so you only need do so once.

Fusible Link Primary Ground Wire 12 Gauge 10FT Protects Wiring Circuit NOS USA Fusible Link Primary Ground Wire 12 Gauge 10FT Protects Wiring Circuit NOS - USA | eBay

This stuff is more expensive than I like to pay, but it will serve you well. You should cut 7" (~18 cm) lengths, strip 1/2" from each end (~1/3 cm) leaving ~6" insulated conductor. (~15.25 cm) Such would suffice for your 60 amp fusible links in a 12-15VDC system.

 

[Big_John]

Main power circuits best work with delayed over-current protection. That's why fusible links were contrived for protecting high demand circuits to start with: they won't interrupt current unless there is a SERIOUS overload.

Ahhh... Nice to read a sentence or two on the subject someone that understands the theory.

"Slo-blow" fuses and delayed breakers have been developed since the 1960s,

I think Slo-blo fuses have been around a lot longer.

 

[saylor]

NO CIRCUIT BREAKER

 

[Ross Wooldridge]

There's a good argument for circuit breakers or resettable fuses as opposed to slow-blow or fusible links in that the quicker the protection is activated the better it protects the circuits from damage. That would be my only concern as to what to choose - how much damage will occur with a slow-blow or link in place rather than a breaker?

 

[patinated_imperial]

A 1966 Chrysler or Imperial won't have any alternator greater than 60 amps maximum capacity. I recommend you get a fresh 60 amp alternator if your power harness is wired to handle that much, as I suspect it is. Are the ammeter wire and alternator charging wire in #10 AWG? .....

...........

This stuff is more expensive than I like to pay, but it will serve you well. You should cut 7" (~18 cm) lengths, strip 1/2" from each end (~1/3 cm) leaving ~6" insulated conductor. (~15.25 cm) Such would suffice for your 60 amp fusible links in a 12-15VDC system....

Thanks for the advice and specially the dimensions to cut a fusible link myself. I saw those rolls advertised, but had no idea what length to make a link. Are there any rules of thumb or calculations for dimensioning a fusible link? Seems like a typical choice is a fusible link one AWG size smaller than the cable. I have a hard time "accepting" fusible links have no current rating . Or at least a current x time rating.

The by-pass cable is 6mm2 (a little thicker than 10 AWG).

I will try to put an amp-clamp on the bypass cable right after start-up to get an idea of the load that cable sees.

 

[3175375]

Thanks for the advice and specially the dimensions to cut a fusible link myself. I saw those rolls advertised, but had no idea what length to make a link. Are there any rules of thumb or calculations for dimensioning a fusible link? Seems like a typical choice is a fusible link one AWG size smaller than the cable. I have a hard time "accepting" fusible links have no current rating . Or at least a current x time rating.

The by-pass cable is 6mm2 (a little thicker than 10 AWG).

I will try to put an amp-clamp on the bypass cable right after start-up to get an idea of the load that cable sees.

this provides guidance:

https://m.roadkillcustoms.com/understanding-fusible-links/

 

[saylor]

There's a good argument for circuit breakers or resettable fuses as opposed to slow-blow or fusible links in that the quicker the protection is activated the better it protects the circuits from damage. That would be my only concern as to what to choose - how much damage will occur with a slow-blow or link in place rather than a breaker?

you miss the safety point. circuit breakers reset.

fuses and links do not.

fusable links are for spike loads where a short-pop fuse would not work as well.

but NEVER circuit breakers.

 

[Ross Wooldridge]

I did seem to miss the point - and I agree one does NOT want self-resetting protection.

 

[saylor]

between all of us this discussion thread will keep alot of people from dying - good work sir

 

[67Monaco]

I did seem to miss the point - and I agree one does NOT want self-resetting protection.

Agreed. If it's a resettable circuit breaker, it will trip immediately again if the short hasn't been resolved. A fusible link would take however many seconds to blow again, allowing more time to damage other components.

 

[Ross Wooldridge]

Agreed - and that's what I was getting at...

 

[saylor]

a fuse link doesnt blow 'again' thats the idea - it doesnt reset itself its a 1 and done.

it just doesnt blow up as fast as a pop fuse - so it can withstand a burst/jolt/high current for a moment - like when a motor starts up or extra electrical load is applied. a fast pop fuse would just pop.

 

[patinated_imperial]

I will report back to this thread, whether my standard OTP fuse blows due to high charging current spikes or not. If so, I will replace with a 14 or 12 awg fusible link. It will be no earlier than March, when the driving season starts over here in the rust belt of Europe.

 

[James Romano]

you miss the safety point. circuit breakers reset.

fuses and links do not.

fusable links are for spike loads where a short-pop fuse would not work as well.

but NEVER circuit breakers.

Circuit Breakers are used in aviation and homes as an immediate protection against over-stressing wires/components, fire, sparking, etc... it's not a perfect system as they can weld closed, get old.. etc. They are the same as fuses. They do the same thing. Main difference is they tend to be beefier than a fuse and can handle more current changes.

BUT.. in aviation they are used as a safety. Much like a one-time fuse popping, you get a second chance with a C/B. Reset it... pops again.. stays popped... circuit is isolated and prevents any further damage to whatever it's controlling. Critical? Land... not critical.. keep on truckin'. Imagine if they were fuses... the Pilot would have to identify and select the proper replacement... oh yeah... no human error factor there. LOL!

Fuses are used in automotive for one reason... $$$. Your car would look like a Piper cockpit, and have a zillion C/B panels all over the place...especially with today's technology. Imagine that box under your dash... Christ... the C/B panel would be massive.