Hey guys,

I have a '66 289 coupe. When the motor is running with the headlights on, I notice they seem to pulse, getting dimmer and brighter. The lights in the dash also do the same thing. This is accompanied by the motor seeming to also pulse. Irecently replaced the alternator but that didnt do anything to solve the problem. Any ideas on whatcould be causing this problem?Thanks.

 

voltage regular, alternator, bad ground (s), its a ford

ok just kidding on the last one

 

[ul][*]it happens on my 65 as well. when you gas it from idle it gets brighter. It shouldn't be a night and day difference tho. Mine is only slight. I've always thought its just because the alt. is turning faster its putting out more juice, thats what i thought. But yeah if its bad check your basics like the battery voltage regulator etc. It shouldn't be to big a deal.[/ul]

 

its also to do with the headlight wiring

40yr old wires, routed thru the headlight switch.

Check out JamesW's website for a cheap effective fix.

http://www.midnightdsigns.com/james/headlights.htm

 

it shouldnt do that 65

start it up, get out your voltmeter and check the battery's voltage while running. should be 13-15ish

check the voltage at your alternator. have a buddy get inside (or pull the throttle linkage) and see if it changes.

 

Mine were doing that too.
I replaced the alt & it was better but still there.
Replaced the voltage reg & that cured it (less than $20 at Advance Auto).

 

That same thing happened on my car... I felt like an idiot when I figured out that I had crossed the wires on my new alternator. The alternator was not charging so I was running off the battery only. I felt like the biggest idiot. So check your wires and also replace your voltage regulator if you have not already done so. I always change the regulator when i rebuild or change the alternator.

 

And for my 3cents:
The alternator can only put out so much amperage at idle due to the speed the engine needs to run and the magnetic field that is created within the stator/rotor of the alternator. The Vreg puts a current to the alternator to increase or decrease the amperage out of the alternators stator which puts a mechanical load on the engine which affects its speed. Usually, a marginal or cheap Vreg will allow for great variations in the field current and the dimming of the lights can be very noticable.
I agree with the t-s'ing suggested, check your wirting connections and replace the Vreg.

 

Voltage Reg,Alternator,Battery or bad ground.It is more than likely one of those or possibly a combination!Good Luck![8D]

 

hey guys,

I replaced the voltage regulator and sure enough that solved the problem. Its running nice and smooth now and no more problems with any lights. Thanks for the help!