Radio dies at idle

[1950 Special Deluxe]

My 1950 Dodge Special Deluxe (D36) Canadian version has a Mopar Model 803 radio. Also labelled as a Philco PD-4908. I had it repaired recently. Now, it works great most of the time.

The only problem is that when the car idles it fades out. At driving speeds it works fine, when I slow down at a red light and the car idles it fades out. When I start to drive it cuts back in. Very similar in operation to the vacuum wipers.

I have a newer Optima battery, generator and regulator must work, battery is always charged.

Car is 6 volt, I replaced the wiring with a home made harness.

Amp gauge shows discharge during start up and goes to charge momentarily and then hovers around 0.

Is there a capacitor in the radio that I should check, I have a copy of the wiring schematic and nothing jumped out at me.

Sorry for the ramble, but I have checked for obvious defects.

Thanks

Neil

[Plymouthy Adams]

I would at this time question the very output of the generator sounds like the car is starving for power...

[1950 Special Deluxe]

I guess I assumed it was working as ammeter does not go negative at idle when the radio cuts out.

I can check by running it at idle and turning on the lights.

Is there another test I can do.

It is the stock generator,

Thanks for the feedback.

[JDaniel64]

Does the audio get distorted as the radio fades out? Any hums or noises that appear/disappear when the radio fades and comes back? Also, when it 'cuts back in' is it instantaneous? Do the dash lights for your radio fade significantly or just a little when stopped? Would just be a few clues to the puzzle   My gut tells me its the vibrator (if its the old style electro-mechanical one), could be weak.

[1950 Special Deluxe]

I will do a bit more research on what happens when it cuts in and out and report back.

I did purchase a new vibrator from Antique Electronic Supply, a P-V105P and installed it.

Says it is for 6 volt positive ground 4 pin.

The radio does not work at all when I install it.

I assumed i ordered the wrong vibrator so have stuck with the original.

Thanks for now.

Neil

[greg g]

Try powering the radio direct from the battery side main terminal of the solenoid. You can do this with a temporary jumper wire. If the problem goes away, then that means there is a problem with where the radio is currently getting power through the main harness.

[JDaniel64]

You didn't order the wrong vibrator, P-V1015P is correct, the new SS vibrator not working is a sign of insufficient power going to the radio. Voltages below 6vdc are insufficient to power a new solid state vibrator, the old mechanical ones will still work but be inconsistent and at a lower frequency. The new SS vibrator I installed in my radio even had a hard time running off of my 6v car charger when testing, they use 14 amps, and can draw down the voltage in a weak power source.

[Don Coatney]

As had been said many times 90% of electrical problems are carburetor related. Increase your idle speed and see if that helps.

[1950 Special Deluxe]

I will try all of these ideas.

I will run a temporary line directly to the radio and see what happens, if that helps I will try the new solid state vibrator.

Also, I will turn up the idle a bit, it could use it.

It will take me a couple of days to report back.

Thanks for now.

Neil

 

[1950 Special Deluxe]

I ran a temporary wire from the Negative post straight to the radio.

It acted the same as before, cut out at idle.

I checked the voltage on the battery, it was 6.27 with engine off and 6.33 VDC at idle.

If I sped the engine the engine up, the voltage meter would climb to approximately 7 VDC and radio would operate.

Let the car back to idle and it would drop to 6.33.

I increased the idle speed and all is well.

Wow, never would have thought that was my problem.

Thanks to Don and everybody else for their help.

Neil

[Don Coatney]

Glad that worked. Sometimes it is the easy fix, other times it is not.

[BigDaddyO]

At what RPM is your idle set?

[Reg Evans]

Does the radio play with the engine off and the ignition switch on ACC ?

[1950 Special Deluxe]

At what RPM is your idle set?

I am not sure at what rpm it would be at.

I just turned it up until it sounded better.

Before it was almost stalling out sitting at a red light.

It doesn't sound like it is too fast now.

[1950 Special Deluxe]

Does the radio play with the engine off and the ignition switch on ACC ?

No, the radio still does not play with the engine off and key turned to acc.

I can live with that.

[Eneto-55]

I could be all wrong here, but my immediate thought was that the battery is weak, or that something in the wiring from the radio to the battery is not a good connection.  These old radios take a lot of power, and I'm not sure if the generator can actually produce enough power on their own to keep it powered at normal idle speed.  (There were songs about playing the radio too much while "parked".)

[austinsailor]

Generators aren't expected to charge at idle. That was one of the big selling points when they came out with alternators in the 50's.

Back then, before alternators were common, some vehicles that spent a lot of time idling, like police cars, were converted to alternators for just that reason.

[Purevil]

Glad the problem was resolved. I agree that the Idle was set to low, in the original post it was pointed out that it was the same with the vacuum operated wipers. As for the electrical voltage... unless it has been switched to a solid state regulator..the voltage regulator could be adjusted to give better voltage at any speed even idle. Ideally a standing battery should be at 2.1 volts per cell (6 volt battery= 2.1volts x 3 cells) or 6.3 volts. 6.33 volts at idle will be fine with ALL electrical accessories turn off but might be to low with headlights, heater, and/or radio turned on. another consideration for increased output is to change to a smaller pulley on the generator, this will cause it to spin faster.