521 electric trouble

[sirchopz]

Ok, guys. I'm having trouble with my baby. I've changed the ALT, BAT,REG and re-wired and grounded the front end of my truck. I left her running for 2 hrs with the lights on until my truck shut-off. What might be the problem I'm going to teardown my dashboard and look to see if I have a short. (note: the fuse for the headlights got real hot, enough to melt a piece of 16 guage wire, why is that?) Any comments would help, I've look at OLDDATSUN.com and printed the service manual I study the electric part of it and did what it comment to do, to check on the charge system. I've gone thru all the post here in Ratsun. HELP!

:(

[banzai510(hainz)]

YOu have H4 lamps with high powered bulbs?

 

put on parking/lamp does it blow?

[sirchopz]

No... Does not blow but the battery juice boogs down real low when your stepping on the brakes.

[datzenmike]

If there is any corrosion on the fuse holders it will add resistance. Resistance will cause heat just like your toaster and get hot. Get the fuse holder as clean as you can or better yet replace it. Once it gets hot the metal looses it's temper and doesn't grip the fuses as tight.

 

Check the battery posts are clean then clean and check where the negative cable bolts to the head. Any corrosion will lessen the amount of voltage available to run the lights and tail lights. Check that the regulator is grounded securely to the body sheet metal too.

[DanielC]

All the above is good info. Questions, when you left it running for two hours, how fast was the engine running? Were all four headlights on?

 

The stock alternator on these trucks only puts out 35 amps, when it is spinning fast enough. At idle, it cannot put out enough current to keep up with all four headlights, or probably cannot even supply enough current for two headlights.

Because a car or truck with a larger engine does not normally run as many RPMs as the L-16 does in the stock truck, the alternator can be "geared" higher so the alternator runs faster at an idle. Do this on the smaller Datsun engine, and you can very easily over speed the alternator.