a nightmare radio issue

I have a 1950 Ford sitting in my install bay with an issue that I can't even begin to explain. I have installed a Kenwood KDC-X300 in the vehicle. Originally, everything was fine. the day following the install, the customer came back. The sound from the radio keeps stuttering. The radio stays on, but the speakers just cut sound for less than a second. This will happen at intervals from once a minute to once a second. This only happens with the car running. With the car off, there is no problem, and this problem is present regardless of the source.
This is where it gets weird. I now have the radio completely isolated from the car electrically. The radio is connected to a seperate battery not connected to the car. I have it connected to a test speaker that is not mounted in the car and the antenna is unplugged from the radio. The problem is still there. With the car running the sound will cut. Car off, no issue. I have swapped the radio to a new unit and the radio itself sits in a wood dash piece. There is no metal of the radio touching the car. Any guidance would be greatly appreciated.

A 1950 ford would have been a 6 volt positive ground system.
Perhaps this is causing the problem.

The car has been converted to 12 volt negative ground.

There is a problem with the voltage regulator. It is going above 14 volts. Use a meter and check voltage on both the red and yellow wires of the deck.

Check for a ground cable from the battery to the chassis of the vehicle. It there is only 1 wire on the ground terminal of the battery, it is grounded to the engine block. The engine block is isolated from the chassis via rubber motor mounts.

Voltage at radio is 13.1 on constant and 13 on accessory. New motor and chassis grounds were added by us as well as alternator wire. All 4 awg

exactly how many speakers are connected to the radio? Also, did you run new speaker wiring at the time of install?


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