Ford Mustang Forum banner

1 - 20 of 21 Posts

·
Registered
Joined
·
24 Posts
Discussion Starter #1
Hello,
I just replaced alternator on my '66 289. Now, the lights are oscillating from bright to dim...any thoughts on the cause??

Just an add to others, I had a new sending unit put in over a year ago...and recently my gauge was only on E. We took out the sending unit and found the plastic float had a small hole in it and caused it to fill with gas...causing it NOT to float. An oldtimer said they used to be brass...just an fyi for everybody.

Dave
 

·
Registered
Joined
·
2,624 Posts
How large is the difference between dim and bright? All older cars did that a little. If you revved the engine, the lights would get brighter, and when you let off, they would dim a bit.
 

·
Registered
Joined
·
313 Posts
Are they flaring from dim to bright or are your lights switching from brights to regular low beams?

If its flaring you might have a loose wire somewhere on the alt to the regulator or even to the solinoid.

If its flickering from low to high beams I would check your floor switch first to see if its broken.

Aim small miss small.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #4
Its a constant flickering...when I open the doors the underdash lights..dim..bright..dim..bright...Now the car, in gear, is doing it also...I can see the rpm's oscillating..not much..but I can tell its not normal..
I found a loose coil wire and it seemed to fix it...and I also made sure the ground on the alternator was tight...but it was fixed for a day or two...now it is back.
 

·
Registered
Joined
·
831 Posts
I assume you are using the old voltage regulator. The flickering is most likely variations in the output from the alternator. Check your connections between the alternator and the regulator. Could have a compromised wire and/or connection.
 

·
Registered
Joined
·
4,555 Posts
Did you tighten your belt enough, with the engine off, if you can put your thumb on the alt fan blades and turn it, it is too loose. You need to put a voltmeter on the battery and see what your charging system is putting out, at idle it is normal for the lights to flicker a little bit, this is because the voltage regulator uses relays and it may be worn out also, a newer electronic relay will give much better regulation. Good Luck.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #9
I ordered a new alternator and a new voltage regulator..along with changing out the points to electronic ignition. Will take it to the garage Monday evening and start the troubleshooting...
 

·
Registered
Joined
·
313 Posts
Do you have an autozone or checkers near you? They will test the battery alternator for problems for free. They can test on and off the car too.
The electronic ignition is a good idea no matter what though. I haven't tried it but I'm going to as soon as I'm able.
 

·
Registered
Joined
·
831 Posts
Do you have an autozone or checkers near you? They will test the battery alternator for problems for free. They can test on and off the car too.
The electronic ignition is a good idea no matter what though. I haven't tried it but I'm going to as soon as I'm able.
Checkers in Florida is a burger joint.:D
 

·
Registered
Joined
·
24 Posts
Discussion Starter #14
oK, so what we did is check the voltage at battery from alternator..it was ok. We changed voltage regulator...lots better. I will announce it fixed. We tried to put in the electronic ignition...but the oreillys part guy sent us the one for dual points...not single points...so we are on hold for a few days. Do we need to use a different coil when changing to electronic ignition?
 

·
Registered
Joined
·
24 Posts
Discussion Starter #15
I year ago I bought a 66 fastback and in that year I have done the following...new= water pump, fuel pump, starter, alternator, carburetor, A/C condenser, carpet, sound deadening underlayment, sending unit, all new belts, oil pan gaskets, new plugs, plug wires..now a new voltage regulator, rally pac, weather stripping, fixed all interior lights...had original automatic tranny pulled and rebuilt..new parts to the center console..new parts for the auto shifter unit...new front glass and back glass resealed..
what is left...new paint, backup lights to work, new rims..and a modern stereo system...possilby install power steering and disk breaks. whew...what a year..but its fast and fun to drive:yup:
 

·
Registered
Joined
·
831 Posts
I year ago I bought a 66 fastback and in that year I have done the following...new= water pump, fuel pump, starter, alternator, carburetor, A/C condenser, carpet, sound deadening underlayment, sending unit, all new belts, oil pan gaskets, new plugs, plug wires..now a new voltage regulator, rally pac, weather stripping, fixed all interior lights...had original automatic tranny pulled and rebuilt..new parts to the center console..new parts for the auto shifter unit...new front glass and back glass resealed..
what is left...new paint, backup lights to work, new rims..and a modern stereo system...possilby install power steering and disk breaks. whew...what a year..but its fast and fun to drive:yup:
Sounds like you have been bit pretty hard by the bug! Keep up the good work.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #18
New inconvenience...I mentioned I changed the sending unit...here is a story. I purchased the mustang about a year ago. The person selling it said he replaced the sending unit recently. A month or so ago I watched in horror as my gas guage went from full to empty in about 2 minutes. So we trouble shoot and we pull the new sending unit. It has a small pin hole and is full of gas. We changed..fixed...until THIS MORNING. I get it out to drive because its a beautiful day...and as I'm driving to work..the gas guage goes from 1/2 to below empty as I'm driving. I assume we will be changing sending unit again..tried to get a brass one...but they don't sell anymore...CRAZY
 

·
Registered
Joined
·
313 Posts
You might have to get one from a junk unit and fit it on a new unit. There are mustang shops that should have it too since its a "correct part". Ebay might have them too.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #20
Just an update...the gas guage is working fine now(gremlins)...I will be changing the pushon plug wire at sending unit to an eyelit...I believe it is just a connection issue..We changed to electronic ignition...starts like a champ and runs great. The a/c unit is now making a loud noise at the unit when I turn it on...I assume the rebuilt is going bad...I also just ordered a new windshield washer fluid motor. Love this stuff..Love getting these things back to working like it was new. Had it over 120mph the other day...no shake, straight as an arrow. I say this because the 66 coupe I owned back in the 80's was fulll of noise and shook above 80. I was a little leary of the mileage guage of 55k, but when you look at the car...no rust..real solid car..it sat for several years and so now I'm working all the kinks out.
 
1 - 20 of 21 Posts
Top