Ammeter bypass

[bronze turbine]

Is this something that is important to do if everything in the car is factory stock? I've heard it should be done if you upgrade the alternator and start pulling a lot more amps than the factory wiring was designed for. I'm guessing the only reason they catch fire is because the connections on the ammeter get loose and get hot?

 

[MoPar~Man]

The instrument cluster amp meter is wired so that all current from (or to) the battery to anything else (except starter motor) flows through it, I think even when there is no key in the ignition. This includes alternator charge current. Ford and GM did not do that (or they stopped doing that way before Chrysler did). Chrysler felt that was a better indication of the condition of the electrical system vs a volt meter.

The firewall contacts and the amp meter itself could fail and cause a fire, I think that's the big issue here. An unnecessary risk given the perceived benefit of having the amp meter.

 

[330dTA]

In a word, yes.

 

[SPF Required]

It is also important to remember that while most of the fine executives at Chrysler in the day likely loved these cars, they still needed to prioritize profits. From everything I have learned, the wiring in or beloved cars is probably slightly undersized for the current it needs to carry. Using smaller wires, saves costs and improves the bottom line.

Just my opinion…

 

[Big_John]

Is this something that is important to do if everything in the car is factory stock? I've heard it should be done if you upgrade the alternator and start pulling a lot more amps than the factory wiring was designed for. I'm guessing the only reason they catch fire is because the connections on the ammeter get loose and get hot?

IMHO, much of the hysteria you'll read about the ammeter is grossly blown out of proportion. It really comes down to poor connections and wire size.

The thing that has not been asked is what your car is. And I apologize for not remembering... But that is important. For example, some of the cars have a "shunted" ammeter that doesn't run as much current through the ammeter. Another bad spot (and probably cause for much more havoc) is the power wire on the 70(?) and up steering column. I've yet to take one apart that wasn't burnt at least a little. Another issue is the wires on the ammeter just plain being loose, and loose causes more resistance which does end up as heat.

That said, the "bypass" isn't a bad idea by any means and if you want to do it, great... The wiring and connections at the bulkhead are getting pretty old and running most of the charging current through some under hood wiring makes a lot of sense and is never a bad idea. Does it need to be done? If everything is good, and you don't have the high current draw, it's probably not going to matter. I have one car that it has been done on and that was mainly because I have some higher draw stereo junk. The other two have not had it done.

There are people that will disagree with me, but whatever...

And great that you said "ammeter" instead of "amp gauge". Correct terminology is always good.

 

[bronze turbine]

The thing that has not been asked is what your car is.

Sorry. It's a '68 Chrysler 300.

 

[cbarge]

Sorry. It's a '68 Chrysler 300.

Having owned several 68 C bodies yes I strongly recommend doing the bypass.
Here is the simplest way..

 

[bronze turbine]

Thanks! That was very helpful!

 

[Lycidias]

I watched the video above, thanks for posting.
To not open another thread:

Is this also recommended for the 73 C bodys?
Car runs with an new ACDELCO 3342212 GOLD 60 AMP alternator and a new voltage reg.

Nothing getting hot right now as far as i laid my hand on it. A large plug behind the dashboard (white) has already melted a bit.
Passing by the old alternator killed the voltage reg. and melted the plastic around a 60? AMP Fuse someone installed near the battery. Before that the alternator killed the old (2021) battery in 2022. The battery already has a new ground strap (2 in total). And the positive cable to the starter is new.

Actually not a problem...but i want to prevent getting one.

@ayilar you know this as C body god? ;)

 

[ayilar]

@ayilar you know this as C body god? ;)

Flattery will get you somewhere, thank you — but the best I can do here is to call on knowledgeable folks like @Big_John @david hill @CBODY67 @71Polara383

 

[Lycidias]

XD well then you'r at least the "person to ask because he knows everybody who knows the answer" ;).

 

[CHARLES374]

Dumb question alert. If you do underhood bypass can or should you still do AMMETER BYPASS ?

 

[CBODY67]

I'm n0t sure what caused the earlier issues, but it's my understanding that the 1972 model year was when things changed, as to Chrysler's wiring of the Alternator gauge. When we got out then-new '72 Newport Royal, I noticed that the alternator gauge barely moved when the engine was revved a bit, unlike our old '66 Newport. I asked the old-line Chrysler service manager about that. He kind of shook his head and said they were now wired "on a shunt", so all of the voltage did not go through the gause like it did before. So I decided that if the gauge moved to the "+" side, all was good.

Factory a/c alternator size should be about 60 amps.

CBODY67

 

[cbarge]

Dumb question alert. If you do underhood bypass can or should you still do AMMETER BYPASS ?

In my opinion, doing the underhood bypass is good enough.
Easy and simple without having to drop the steering column and pull the instrument cluster.

If anything, I would run an extra feed wire straight through the firewall bypassing the bulkhead connector.
The bulkhead connector is knoen to cause issues.
The heavy red wire with a fusible link at the bulkhead is the main feed.
Ok...
Cut the main feed at bulkhead both inside and outside.
You can either drill out where the wire goes through the bulkhead, or drill a new hole in the firewall.
At the starter relay run 10 guage wire using a 14 guage fusible link.
Thread wire through the firewall and connect to the red feed wire you cut at inside the car at bulkhead.
I prefer soldering this connection instead of butt connectors.
You can go one step better by threading the feed straight to the + side of the ammeter guage-- but again pulling the cluster. I did that on my 68 Newport since I had the car tore apart anyways.
Check operation of vehicle and accessories.
You may have to feed the accessories a separate wire if they dont work. ( power windows, locks, etc.)
Any questions PM me.
Hope this helps.

 

[Lycidias]

I'm n0t sure what caused the earlier issues, but it's my understanding that the 1972 model year was when things changed, as to Chrysler's wiring of the Alternator gauge. When we got out then-new '72 Newport Royal, I noticed that the alternator gauge barely moved when the engine was revved a bit, unlike our old '66 Newport. I asked the old-line Chrysler service manager about that. He kind of shook his head and said they were now wired "on a shunt", so all of the voltage did not go through the gause like it did before. So I decided that if the gauge moved to the "+" side, all was good.

Factory a/c alternator size should be about 60 amps.

CBODY67

Okay!! If this can be confirmed it would be great! The gauge don't move pretty much. Just slightly to the right, when the car is running. But not even leaving the white spot in the middle.

When the alternator blew everything up it moved one time while driving heavily to the right an then felt down to the middle.

Definitely the generator and volt regulator were causing this problem. It's gone since everything is new.

 

[ayilar]

"person to ask because he knows everybody who knows the answer" ;).

To be clear, I only posted a few names -- my list was not meant to be exhaustive. @cbarge is a perfect example of someone who is a fantastic source of technical knowledge and is always generous with sharing it (Medina, my 1971 Monaco, has been a direct beneficiary), yet whom I did not mention when responding quickly on my phone.

 

[73Coupe]

.....snip.....
Is this also recommended for the 73 C bodys?

1973s have a factory shunt setup, no need for bypass.

 

[Lycidias]

Thank you very much sir.

 

[72RoadRunnerGTX]

Having owned several 68 C bodies yes I strongly recommend doing the bypass.
Here is the simplest way..

Curious, to those who promote this band-aid approach, just how does it make this charging system “safer” when it by-passes completely or adversely alters the designed circuit protection for all unfused factory wiring?

 

[Big_John]

Curious, to those who promote this band-aid approach, just how does it make this charging system “safer” when it by-passes completely or adversely alters the designed circuit protection for all unfused factory wiring?

The big reason is the old wives tale about the ammeter bursting into flames and kidnapping the Lindberg baby.

I watched this video yesterday (thanks) and it made a lot of sense to me. I've been of the opinion that most cars don't need this, but it's not a bad option. Your video has me rethinking that.

There is so much confusion and misinformation out there about the charging circuits that it's tough for guys to know exactly what to do. I've even seen some really bad, burn your car down type things happening. For example, I've read of guys putting large fuses on small wires... Thus the wire would burn way before the fuses would blow. I tried explaining that one and common sense did not prevail.

One recently was using Home Depot wire to do a "bypass" (at least it was stranded). I quickly realized that trying to explain that automotive wire was built to take the flex and home wiring wasn't would have fallen on deaf ears and 10 guys would have defended using that wire.