lights surging

[Virg464]

Looking for possible idea to track down for an issue (maybe it's normal). 66 Coronet, not really a street car, rough idle, built/building the entire wiring harness for the car. Starts and runs fine, running lights, hi-low beam, gauges, elec cooling fans, elec fuel pump. Everything works, but when it's running and I let it idle (approx 950-1000 rpm), the lights surge (intensity), the fuel pump rpm surges (pressure stays constant 7 psi). Running a 60 amp OEM alt, using an OE style electronic voltage regulator, MSD 6AL ignition. Off idle that all goes away.

I know this is a very general/non specific question, so any thoughts are appreciated.

 

[Aron Gleason]

I'd check all of your grounds.

 

[Geoff 2]

It could be the alt is on the threshold of charging, ie the alt output voltage needs to be higher than the bat voltage; alt voltage could be changing/varying slightly at this changeover point, which could explain why the problem goes away with more rpm which will increase alt output.
If this is the case, a slightly smaller alt pulley will likely fix the problem.

 

[toolmanmike]

Looking for possible idea to track down for an issue (maybe it's normal). 66 Coronet, not really a street car, rough idle, built/building the entire wiring harness for the car. Starts and runs fine, running lights, hi-low beam, gauges, elec cooling fans, elec fuel pump. Everything works, but when it's running and I let it idle (approx 950-1000 rpm), the lights surge (intensity), the fuel pump rpm surges (pressure stays constant 7 psi). Running a 60 amp OEM alt, using an OE style electronic voltage regulator, MSD 6AL ignition. Off idle that all goes away.

I know this is a very general/non specific question, so any thoughts are appreciated.

Put a voltmeter on it and make sure the how much the voltage is surging. It probably needs a regulator. The old point style regulator can be replaced with an electronic one that looks like the old one. Just make sure the case is grounded well to the firewall. A poorly grounded case will cause overcharging.

 

[493 Mike]

Put a voltmeter on it and make sure the how much the voltage is surging. It probably needs a regulator. The old point style regulator can be replaced with an electronic one that looks like the old one. Just make sure the case is grounded well to the firewall. A poorly grounded case will cause overcharging.

"using an OE style electronic voltage regulator"
In case you missed this.
Mike

 

[ckessel]

Get that on the wagon, at idle, with the LED's on. Going to get a relay pack/bypass setup from Crackedback in the near future.

 

[Sinitro]

It seems the alternator is having marginal output @ 950 RPM, given the accessories current draw the regulator is kicking in/out..
Suggested solutions are:
1. Revise alternator pulley size
2. Upgrade the alternator to a higher output one

Note a higher output alternator will supply more current @ a lower RPM than the present 60 amp one.

Just my $0.02...