Dash smoke

Scoopy G

Scoopy G

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Hello fellas (and fell-ettes) from sunny warm Tampa. Yesterday I was driving the '67 Newport Custom, when I noticed an odd smell. I stopped and had breakfast, and took off again.

The smell came back, and I glanced down to see smoke coming from under the dashboard. I pulled off the road but the first place to pull into was a gas station! I kept going to the next driveway, but it was a day-care center! I was close to home, so I just drove there.

The smoke was brief and not much more that a puff. When I got home, I got the light out and a mirror, but could not see any burnt wires.
The ammeter bypass has been performed on this car (5years ago), and I didn't notice any burnt fuses. I got back in the car and continued driving it around town with no further issues. Hmmmmm.....

DSCF0592.JPG
 
Scoopy G said:
The ammeter bypass has been performed on this car
Click to expand...
I used to be a proponent of the bypass, but after reading and watching @72RoadRunnerGTX 's videos, I came to the conclusion that the bypass does more harm than good as you lose a lot of protection for the dash wiring. It took me a bit to wrap my head around that, but once I understood, I removed it from my car.



He has some other interesting videos on the subject too.
 
Big_John said:
I used to be a proponent of the bypass, but after reading and watching @72RoadRunnerGTX 's videos, I came to the conclusion that the bypass does more harm than good as you lose a lot of protection for the dash wiring. It took me a bit to wrap my head around that, but once I understood, I removed it from my car.



He has some other interesting videos on the subject too.
Click to expand...

Great information in those videos.
 
BTW, I recently dug out that “Fixture” and revamped it a bit for a new series of videos on common “vintage” Chrysler electrical systems that I am currently working on. Will go back over some of the material covered in last year’s videos, expanding out a bit on some other related circuits and common issues. A new tool to track(see) resistance(heat). Some C-body related, or specific issues will be covered as well, including a somewhat detailed explanation, demonstration of the later externally shunted ammeter. First few videos are up now.
S2E1
 
Instead of doing the bypass I think the best thing you can do is eliminate all that amperage from passing thru that amp gauge circuit. Anything that pulls a lot of amps try to find a different power supply closer the battery main power. The alternator can go directly to the battery instead of running thru the amp gauge circuit. Of course if you do this your amp gauge will not be reading correctly so I switch to a volt gauge. I also converted my headlights and headlight motor to relays so now the only current flowing thru the wiring under the dash for the headlights is to control the relay so not much at all. A good starting point is the bulk head connectors, see if they have corrosion and clean them, even if they don't show corrosion. Use a good electrical connector cleaner and when you reconnect them use deionized electrical connector grease to keep them from corroding. I love my Mopar's but every one I have owned had wiring issues from my first 70 Dart to my 96 2500. The 2500 actually left me with no headlights late one night miles from home, the headlight switch let out it's magic smoke, the headlights blinked a few times then were gone. I ended up jumping a wire from the battery directly to the dim circuit to get home. After that every Mopar I have owned has been converted to relays on the headlights. Switching to LED's headlights might also fix this, I'm not sure. The key is to divide all that amperage that was passing thru the amp circuit to different ones.
 
72RoadRunnerGTX said:
BTW, I recently dug out that “Fixture” and revamped it a bit for a new series of videos on common “vintage” Chrysler electrical systems that I am currently working on. Will go back over some of the material covered in last year’s videos, expanding out a bit on some other related circuits and common issues. A new tool to track(see) resistance(heat). Some C-body related, or specific issues will be covered as well, including a somewhat detailed explanation, demonstration of the later externally shunted ammeter. First few videos are up now.
S2E1
Click to expand...

Funny you mention that video... I had it cued up to watch when I had a little time with no distractions. It's been a few days LOL... Going to watch it while eating lunch.
 
Toolmanmike said:
I am surprised the manufacturers used amp meters back then.
Click to expand...
Interesting, a Mopar Performance P-number. Would that indicate the harness smoke level somehow relates to performance? Funny, not really seeing a need for replacement harness smoke, these harnesses seem to have the potential to generate an unlimited amount of smoke over and over again in the right hands.
 
MONC440 said:
Instead of doing the bypass I think the best thing you can do is eliminate all that amperage from passing thru that amp gauge circuit.
Click to expand...
The C body ammeters are more than capable of handling the current a C body will see, and then some. The best thing to do is bypass the bulkhead connector, that is a definite weak spot. Thanks to 72RoadRunnerGTX for showing us that in a previous thread that covered the ammeter bypass.
Headlight relay harnesses are practically mandatory with how old the wiring in our cars is, and how much power halogen bulbs can draw. Especially because if you do any kind of high speed driving you absolutely want headlights that let you drive as fast as you can see. But you should connect the power feed for this to the alternator output stud if you want to do it properly and have the ammeter also function properly, which means the bulkhead bypass is still needed.
A solid state voltage limiter/regulator that replaces the dash one is also great insurance since one of the failure modes of the mechanical limiters is to let 12 volt power straight into the gauges which will fry them...hope you've got replacements. If you have an external voltage regulator for the alternator, replacing that with a solid state one too will also let you install electronic ignition, or other things that are sensitive to voltage fluctuations.
 
idk what law of physics is involved, but when a wire fries ,it starts at both ends and works its way to the middle...so pay attention to connectors as a source... poorly crimped connectors on your bypass could be the issue...these were the previous owners bulkhead repairs on my car...and I never saw any smoke, it was all functional and found them while replacing the evaporator core
 
Last edited:
Thanks to everyone who responded to my post. I loved the "Mopar replacement smoke" post, that was hilarious.

None of the electrical functions on the car are disabled; all lights, fan, wipers etc. work just fine. As I looked under the dash with bright light and mirror, I could not see any burnt wires, but of course they could be somewhere out of sight.

I purchased a fire extinguisher, and I now disconnect the battery when the car is parked in the compound.

Best regards for the Thanksgiving holiday to all C-body enthusiasts. Safe Travels.

Richard in Tampa
 
I had a similar smoke issue on the dash of my 67 Coronet once, more than twenty years ago. A puff of smoke for a few seconds and then the smoke was gone. The smoke turned out to be the voltage limiter on the back of the gauge cluster. I then replaced it, but it took alot of trial and error to figure out that I should have replaced the ballast resister, and voltage regulator, and electronic ignition control box, at the same time. I ended up chasing one electrical problem after another replacing each component one at a time, more than once, before getting the electrical system working again as it should. Replacing all three together at once solved all my electrical gremlins. Even replaced the alternator a couple times (really not sure, but I think the alternator was getting fried by the other damaged components). I deduced that the voltage limiter had damaged another component which resulted in a continous domino effect till I replaced everything at the same time. the car has been reliable ever since with no electrical issues.


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