MTFCA Forum

Driving the car during the day, everything is fine.

Drive the car with the lights on and it is significantly different. It loses power.

I am currently only running on battery. I know the Mag needs to be charged. It quit a couple of years go.

Diagnose my problem. And......GO!

How is your generator running? Your voltage drop increases with speed as the coils are buzzing more frequently and it is drawing current to run the points. It appears that you might be drawing down the battery at a greater rate than the generator output.
Norm

Norman Kling wrote: ↑

Sat Nov 07, 2020 7:11 pm

How is your generator running? Your voltage drop increases with speed as the coils are buzzing more frequently and it is drawing current to run the points. It appears that you might be drawing down the battery at a greater rate than the generator output.
Norm

It appears to run fine. I start the car and it reads "Charging"

Check for a bad ground or better yet, attach a ground wire from the frame to the engine block.

Hope this Helps,

Hank

Henry K. Lee wrote: ↑

Sat Nov 07, 2020 8:04 pm

Check for a bad ground or better yet, attach a ground wire from the frame to the engine block.

Hope this Helps,

Hank

Can you explain in more detail?

A poor ground is just as bad as a bad positive connection. Installing a known contact (bond) depending on the overall condition of your vehicle, will prevent over current drawing. I always install a #10 or #12 wire from my ground from the battery attachment to frame and to one of the lower bolts at the ball attachment at U-joint. Never have electrical issues. I have owned British cars! LOL.

Hope this Helps,

Hank

Another place to install a ground strap is between the engine and the frame.
Norm

Ok, tried it Either I didn’t make the contact surfaces clean enough or something else is going on.

I attached a #12 solid copper core wire from between the ground strap/frame to a bolt in the the universal joint

I drove the car with the lights on. I still have power loss. I’m going to scrounge up three 12 volters and recharge the mag.

How old is the battery and have you had it load tested? Could be the battery just needs replacing.

Works with lights off, not with lights on, its your battery and generator. Gen 3rd brush may need adjusting, but with lights on you will get a slight discharge anyway. A fully charged battery should run the coils and lights for a couple of hours, running during the day for a couple of hours should recharge a good battery.

1 have battery checked and replace if bad
2 adjust 3rd brush for your driving conditions per the Ford Service Manual.
3 if you run at night with lights you should run it again in daytime without lights to recjarge the battery, if unable to run at daytime put a battery charger on it befor running at night again.
4 if you want to run a ground strap from your frame to the engine it should be like the ground strap on the battery, if you run wire it should be like your battery cable: 0 or 00 gage.

Need more info:

How many amps does your generator put out with the lights OFF?

How many amps does your generator register with the lights on? (it will be negative)

What kind and how many lights do you have and what's their total amp load?

Weak and old batteries, poor connections and grounds need to be eliminated. But in the end, you don't have the available amps to run the coils efficiently and the lights too without a lot of reserve capacity in the battery or advancing the 3rd brush beyond the generator's safe output. The cheapest route is just to recharge your magneto and get it working correctly. Your other options are switching to an alternator, replacing your current bulbs with LED bulbs, purchasing a Optima (or similar) with a higher reserve capacity.

Mark Gregush wrote: ↑

Mon Nov 09, 2020 2:05 am

How old is the battery and have you had it load tested? Could be the battery just needs replacing.

Battery is probably in need of changing out

I went the alternator route when I finished the car in 2011 but it never worked correctly. I eventually sold it