Strange Electrical Problem

As some of you may know, I recently replaced my alternator. This problem was occurring before the alternator was replaced, so I don’t think that’s the issue.

When the engine is off, all electrical works fine. When engine is running, the following problems occur:

- radio goes haywire. No sound at all when tuned in to a radio station. Bluetooth mode gets very choppy and quiet. Screen gets pixelated.
- if I go anywhere near the Jeep with a multimeter, the meter starts tweaking out. Oddly, the Meter on my timing light reads voltage just fine.
- turn signals and hazard lights flutter so fast that you can barely tell they are blinking. Headlights and taillights work fine.

again, all these things work totally fine when the engine is off.

I tried running the engine with the alternator disconnected from the battery and the problem persists.

Any ideas what could be going on here?

 

Do you have the negative battery terminal grounded to the body,frame, and motor? Also make sure all of your accessories are solidly grounded as well.

 

X2

 

I checked continuity between frame, motor, body and negative battery post, and they were all solid. Is that enough? Or is there more to ensuring they’re all properly grounded?

also, for what it’s worth, I installed the radio, lights and turn signals this week. Prior to that, I had literally zero accessories. It was just four wheels and a motor. And Even then, I still had the problem where the multimeter was going haywire anywhere near the Jeep.

 

steel core spark plug wires might do that. it was an option on 60s muscle cars and required radio delete on the package.

 

The plug wires are copper core. label says “super stock copper core 8mm.” They seem relatively new. Very clean, soft and flexible, etc.

 

Well there's your problem!

 

Yep. Solid core wires are like broadcast antennas for 4 or 6 or 8 spark gap generators. Copper wires will send out lots of broad-band interference and clobber anything sensitive nearby. Marconi transmitted radio across the Atlantic with a spark gap. You need resistor core wires, aka suppression wires.

Ignition suppression condensers may also help, but you need suppression wires. Resistor spark plugs will also help, though most are already.

 

This is why Petronix says not to use solid core wires with their Igniter triggers.

 

Yet, plenty of cars had radios and solid core wires in my youth.

OTH, the M38A1 has totally shielded wires, with grounded coaxial wire mesh jackets.

 

Thanks. That sounds like my exact problem, even down to the brand of radio they were using. Every single forum I’ve been on, I’ve never been able to get the search function to pull up useful results.

anyway, I ordered new plug wires. Plugs will be next if that doesn’t 100% fix the problem.

 

When I first finished my Jeep, in 07, I was sitting a bar Up North and a member of the club, an older Member, ask did I have solid wires on my Jeep, I said yes, He said his TV went all craze when I went by his house. I didn't have a radio yet, so I didn't realize it was doing that.

 

A spark is very broad-band, sending out EMI/RFI (electromagnetic interference / radio frequency interference) over the whole spectrum. You do get some shielding from the car body, and radio chassis used to be built inside a steel box which was grounded to the car body. Plus they would filter the incoming power, so that the RFI was not transmitted to the radio through the power input. I recall that fiberglass body cars (Corvettes) had their own extra RFI shielding around the distributor and wires - to make up for the lack of shielding from the car body. It's not surprising that devices lacking shielding like a multimeter or TV would be sensitive to this RFI.

Contrary to what Pete writes, I don't remember a time when there were not suppression wires available for all cars. The solid core wires have always been the domain of race cars and hot rodders as I can remember. Possible vacuum tube radios were less susceptible to RFI, or that those radios were built to shield from the EMI. What I would guess, is that car radios that existed were the domain of the wealthy until the mid century, and resistance plugs and wires were developed to go along with their entry to the mass market. Certainly in the teens (like in the era of Pete's Model T - doesn't Pete have a Model T?) radios for the home were an expensive and prestigious item. Putting a radio in a car would seem prohibitively expensive for all but the wealthy in that era. Tubes were the only game in town, and were not significantly miniaturized until post WWII and later.

 

Timgr, I accept and admire your technical knowledge. But I have a very different impression of the the historic chronology.

Yes, I do have a Model T. But well into the Fifties and Sixties solid-core ignition wires were the norm, in my mind. Radios were an available dealer accessory at least as far back as the '30's.

I clearly recall the first time I discovered a carbon-core suppressor wire and thinking "WTF?!?!?" That was probably in the 1970's. (Although, admittedly, I've never owned a new car.)

Now I'm curious to know for sure what the facts are.

P.S. ... a little googling makes me suspect resistance type wire may have started to come in along with "Electronic Ignition" as it emerged in the late Sixties. (?)

 

Fiber coil wire to dist and tie a knot in it.

 

This is true. Also resistors in the sparkplug boot.

Personally, my tin-foil hat always kept the static to a minimum as I received messages from the Mother Ship.

 

How many nanohenries in that knot?

 

Installed new plug wires today and it seems to have fixed the problem entirely. I had returned the radio to amazon because I thought it was faulty. So I’ll need to order another one and hopefully it works fine. But the turn signal problem is 100% fixed. Thanks everyone!