Ammeter bypass

[72RoadRunnerGTX]

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.

Funny, I’ve been battling misinformation/misconceptions about this charging system since my days working at the dealers back then. More recently, on-line on the various Mopar forums for years. Amazes me how the myth of the “spontaneously combusting” Mopar ammeter just continues on and on unabated and people are still just eating it up. The old “If I read it in a magazine/on-line article or post, it must be true” syndrome. Sometimes I’m met with a lot of uneducated push-back.

Several more recent YouTube videos promoting this bypass without mention of the serious added risk are just outright dangerous. One guy shows what appears to be 4/0 ga cable connected at the alternator stud straight to a battery clamp bolt. Freely admits he sourced the “commercial grade” cable for free from his place of employment. Then gets belligerent when questioned about its safety in a comment.

Loading this charging system correctly seems to be another area of misconceptions, folks just can’t separate this system from everything else these days. Clamping everything to the battery then when bulkhead or ammeter connections fail, must be the ammeter that’s the problem.

I too, have had numerous conversations over the years about why solid core, or stranded, house wire should not be used in any moving vehicle.

 

[bronze turbine]

The way I see it, there's nothing inherently wrong with the design from the factory. The only thing I can see being a problem is that since all the power for the whole car goes through that ammeter, it could get hot and start a fire if the connections got loose or dirty. I think it's only a 30A alternator on those cars so not a lot of power goes through it anyway. Now when you add a lot of power consuming upgrades and upgrade to higher output alternator, you're going beyond what the engineers envisioned for that design. Chrysler engineers themselves addressed this over the years because I know by 1976 the ammeter didn't have the total power going through it and it was more of a shunt type thing or actually was a voltmeter labeled as an ammeter. If you did the update the way the factory did it I can only see that being a good thing. But, if you do a hack job there's no doubt you could actually be creating more problems then resolving.

 

[72RoadRunnerGTX]

The only condition where full vehicle loads run through the ammeter is when the engine is not running or running and the alternator has failed. During 99% of the operational run time, there should be little to no current flowing through the ammeter, only battery charging current, ammeter needle centered or close to it. For C-bodies the switch to a shunted ammeter was around ’72-73 as I recall.

 

[MoPar~Man]

Can you (or someone) explain the difference between the 2-field-wire vs the 1-field-wire alternators?

Your diagram shows the second field wire on a blue-wire bus running through bulkhead connector 23 to the ignition switch. I'm not sure what functionality is happening with the ignition switch and the alternator there.

 

[72RoadRunnerGTX]

Can you (or someone) explain the difference between the 2-field-wire vs the 1-field-wire alternators?

Your diagram shows the second field wire on a blue-wire bus running through bulkhead connector 23 to the ignition switch. I'm not sure what functionality is happening with the ignition switch and the alternator there.

In 1970 Chrysler switched to an electronic, or solid state, voltage regulator for this system. Along with this change was the use of a “dual isolated field” alternator. Both field contacts being insolated from the alternator chassis ground. Full ignition 1 line voltage in on one side, with the regulator now regulating field current on the negative side of the field coil contact.

1969 and earlier single field alternators grounded one side field contacts to the case, with the mechanical regulator regulating field current on the positive side through the one insolated field contact.

The diagram references the 1970 and later wiring but is unrelated to the charge output path for the subject of the video. Same basic layout since 1960 through the seventies, or for C-bodies, until the change to shunted ammeters.
The specific bulkhead terminal locations are referencing B & E bodies, may not match some C-body applications, general reference only.

 

[MoPar~Man]

Related video:



See also:

Catalog

(AMP gauges at the dash are troublesome. They should be by-passed, and then install a VOLT gauge.)

 

[72RoadRunnerGTX]

http://[URL][URL][URL][URL]http://www.madelectrical.com/electricaltech/amp-gauges.shtml

[/URL][/URL][/URL][/URL] (AMP gauges at the dash are troublesome. They should be by-passed, and then install a VOLT gauge.)

I couldn’t disagree more with that statement. Really, the Mad Electrical article? Read the preface carefully, it was written to address the later seventies Dodge truck plastic cluster framed ammeter fiasco. The passenger car ammeters/cluster are not constructed the same. This is has been the number one article most cited by the promoters of ammeter misinformation for many years.

 

[MoPar~Man]

Don't agree with that statement at all. Really, the Mad Electrical article? Read the preface carefully, it was written to address the later seventies Dodge truck plastic cluster framed ammeter fiasco. The passenger car ammeters/cluster are not constructed the same. This is the article most cited by the promoters of ammeter misinformation.

If you are refering to the statement that I put in brackets, I just put that there because it's the title of the article. When I posted the link and then saw that it appeared as just the word "Catalog" I went back and added the title of the article.

I agree with your analysis that the ammeter bypass using a heavy gauge wire from the alternator to the battery is not safe, at least not without a fuse or circuit breaker. There are better options vs just a fusable link. A failed alternator seems to be overlooked by many, it is perhaps more common than a failed ammeter.

And yes, the advent of more electrical accessories in the later 70's particularly in the trucks seems to have been the catalyst for the backwards-looking at the older cars and thinking that they too must need the ammeter bypass.

I myself have just replaced all the packard contacts in the bulkhead connectors on my '67 Monaco. I don't have A/C. But I can say that the heavy gage power in and out pins on the connectors were melt-damaged but still present - if barely.

I think better circuit breaker protection (to replace the fusable link) is possible, and could also be added at the B alternator terminal.

Putting the bulkhead power connectors into a good condition, and checking your ammeter posts and connections are clean and tight, is I think also necessary. But not the bypass.

 

[72RoadRunnerGTX]

The bulkhead connector charge circuit Packard terminals are/were by far the weakest link in that original design. They should be bypassed altogether with a direct wire run through the firewall separately, directly through to the ammeter, as was the later “fleet bypass”. There is no need at all for a disconnect at the firewall for that circuit. Followed by close inspection of the ammeter terminals and insulators, correcting as needed.

Details of this recommendation were covered in this video on the consequences misplaced added loading to this system.

 

[MoPar~Man]

If you've looked at or replaced the bulkhead connectors or are otherwise satisfied that they are ok, I would just add parallel lines through the bulkhead to the ammeter instead of cutting the existing wires as you describe at the 13:00 mark in the video.

For a stock, un-altered car, adding a headlight relay circuit under the hood, powered off the alternator output, would give the biggest benefit for taking load off the existing bulkhead connectors. For those that have added an electric radiator fan, taking power from the alternator output instead of the battery is also the way to go.

 

[72RoadRunnerGTX]

Those two Packard terminals at the bulkhead connector have been failing since these cars were new. They served one purpose, to allow for a quicker assembly going down the line at the factory. There is no electrical need for them. They are not rated to handle anywhere near the expected/designed stock loads, let alone any added loading. C-bodies typically run more stock loads (A/C, power windows) than other platforms and the higher rate of melted alternator feed Packards showed it (pre-shunted ammeters). There was a C-body recall (Recall 48549) to specifically address it in the mid-seventies, adding a parallel 12ga wire from the alternator to the fuse box.

The referenced mod in the video you mention is commonly known as the fleet by-pass, also involves upsizing the wiring to handle added loads correctly. Not going to terminate new 8ga wire runs at the bulkhead connector when that is the weakest link in the whole system. I avoid parallel wire runs whenever possible, would rather un-wrap harnesses and replace/repair/upsize conductors as needed then re-wrap.

 

[edbods]

Clamping everything to the battery then when bulkhead or ammeter connections fail

wouldn't running the wire from the alternator to the battery positive, then connecting ancillaries like headlights or similar as well to the battery positive also cut down the load on the stock wiring?