pulsating lights

    what makes the headlights and dashboard lights surge, as if someone had a dimmer switch on the lighting system and was making the lights go bright and then dim and then bright and them dim and .... rapidly..but not all the way bright and then dim,...just a bit, but very noticeable? just had the alternator tested, it is fine. it's a '66 hipo.. Thanks.

    The pusling that you are noticing is a normal characteristic of mechanical voltage regulators with alternators. There are two sets of contacts in the regulator, a high and low, and they will cycle back and forth depending on the demand placed on the charging system by the battery and the car's electrical load. There are adjustments that can be made inside the regulator to the spring tension at the contacts, but it is not one that many mechanics are familiar with any more. The pulsing is most obvious when the battery has been discharged and the alternator and regulator are trying to provide a higher current to recharge the battery. If you use a battery tender when you store your car, or drive it often you will probably notice it less as the battery is nearer to a state of full charge.


    Edited by - round2K on 09/22/2007 22:15:40

    I agree with round2k, i replaced mine with a modern electronic type and put the cover from the original on it and it works perfect, the running voltage is steady as a rock

    any other suggestions?, have replaced the voltage regular, same problem, will replace light switch next....fortunately I have extra parts from other mustangs and it hasn't cost me a penny yet (just my time) to test the alternator, battery, voltage regulator. ..

    These are all very valuable suggestions. However, before going to the expense of changing all these parts, I would suggest checking and cleaning all you're earth points. Many electrical faults such as the one you described occur simply because the negative is not making good enough contact to the the chassis. Cheers Tony

    Behind the instrument cluster there is a ground for the dash harness that is worth investigating. If you are very limber you can reach it without pulling the cluster. If not, you can undo the speedo cable and pop the cluster loose.

    I know the ground behind the dash you are talking about, I'll pop the cluster to ensure it is secured, and check all other ground points per our friend from Australia. btw, I have already replaced the voltage regulator and light switch, (after fully charging the new battery, and testing the alternator) with good parts from another project car, so haven't incurred an expense yet.

    From symptoms I would be very surprised if the earth behind cluster is the problem. I believe that you're headlight earth(should be next to headlight connectors behind front bumper) is faulty. When lights are turned on they are trying to find an earth return elsewhere,ie. through wiring harness and probably to the earth behind you're dash(so it must be ok). I thinking that you probably have dash lights illuminating that should not, and they are not at full brightness. Also check other main earths particularly on firewall.Cheers Tony

    all good suggestions, will do a down (ground) to earth check the next few days... car is all new, maybe not getting a good ground due to repainting everything.... need to scratch it up a bit. btw, it's not just the headlights, it's the interior lights doing it at the same time as the headlights, (in harmony) and I bet if the radio worked and I turned it on, the volume would be going up and down too.

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    btw, I have already replaced the voltage regulator...

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    Pat, did you replace the voltage regulator with a modern solid state unit? I was having exactly the same issue with my car using one of the AMK repop voltage regulators. Put in a new Motorcraft regulator and problem solved.

    Dave
    6S1757

    Good point from Dave,

    Had exactly the same issue on my 65. The AMK repro

    regulator is probably made to factory specs while

    their alternator has a higher amp output. This may make them

    incompatible with each other. Tested two repro regulators and

    the problem was the same. Used an eletronic regulator with

    the cover from one of the AMK repros to look correct and the

    charging system has since worked perfectly.

    /Bo

    I meant to ask if the car has been repainted as I’ve come across this before. Paint is not a very good conductor. Keep in mind that headlights draw a lot of current, and everything probably works fine with the headlights off. Anyway, good luck. Tony

    You can still get a Motorcraft regulator from Ford, don't remember the part number off hand but the old points style is no longer available anyway. I'm sure you can get it after market at PePBoys, Autozone, etc.

    Dave
    6S1757

    Is the pulsing of the lights on a regular interval, or intermittent?

    If it's on a regular basis, I would suspect regulator, or possibly dirty ground connections as mentioned. If it is irregular, I would suspect a short in the harness possibly at a thru panel hole.

    Check the harness from front to back, sometimes when a previous owner has cut a wire, then stripped the end & twisted it back together, then taped over things, it can corrode and cause problems.


    Edited by - 66tiger on 10/02/2007 14:26:31

    the lights, in fact, I believe it's the who electrical system is flickering... I'm pretty sure it is a grounding issue.... the headlamps I have are original style....original type...

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