76 400 electircal issues

[kreechur]

Hello,

I have a 76 400 that i recently got running, and when i revved up the engine, the headlight blew out. I bought a new headlight, and a new universal voltage regulator since the original is not available, and it was fine in my garage. I took it for a ride around the yard, i barely got out of the garage and the headlight burned out again. I did not have a tail light in at all during this, so not sure if it would have blown also. Perhaps i got a faulty regulator? Or is there another issue i should check within the wiring? Was a universal voltage regulator the wrong way to go even though it looks exact to the original one that was in there?

Thanks,
Scott

[JDT]

Most any voltage regulator will work.

But no voltage regulator will work if it is not hooked up correctly.

Two more important things to check are the ground and the heatsink.

The OEM unit has a small aluminum block mounted between the regulator heat sink and the sled chassis.
This is a likely place to find corrosion. That white powdery stuff has to be removed to maintain a good heat transfer and ground connection.
A wire brush or file will do the job. A coating of dielectric gel or heat paste is agood idea also.

The ground wire(green, brown or black) has to have a good ground connection. It will not ground well through painted surfaces so check the conection with an OHM meter.
The hot wire(red or yellow) needs to be conected correctly also.

There is a wiring diagram for your sled in the Tech Section of this forum. Check it against you sled to insure that someone in the past has not modifed it.

It is very common to find wiring messed with on old sleds past through many hands over the years.

The factory engineers knew what they were doing and it will work best that way.

But a Voltage regulator can be bad right out of the box new, Especially if it was made in CHINA!

[JDT]

duplicte post....

[kreechur]

Thanks I'll check the continuity and wiring at my next chance. The heat sink was there and it was clean when i installed it. The ground was hooked up, but i never did check continuity. I had to add a section of wire since the wire on the new regulator was too short to reach the plug.

[JDT]

You'll want to ensure that all the ground conectors are good all the way back to the engine itself.
With one lead of the meter on the engine it should read the same to any ground point or ground wire on the entire sled.
Less than 1 ohm max. Closer to 0.0 the better.

[JDT]

Here is a factoid,,,,

If the headlight burns out the tailight will immeadiatly follow.

If the tailight burns out it will probably have no effect on the rest of the lights.

It is normal to have the lights dim at idle. As revs increase voltage will increase and the lights get brighter.
If the regulator is weak or faulty or unhooked the lights will get real bright but only for a moment....

[kreechur]

I was talking to someone who suggested that there is a jumper wire for the electric start kits that may have been moved? He said that it's for if when you have an electric start kit in and you decide to run without a battery hooked up that you need to change this jumper wire. My sled does not have the kit installed, could that jumper wire being referenced be an issue? If so where is it, and where should it go to?

[Matt]

There should be a large connector near the recoil housing of the engine, facing out toward the belly pan. It should have plug in it, with some jumper wires. It shouldn't be missing unless it had electric start that someone removed.

[400brian]

Yes there is a jumper wire that is removed when you plug in the e-start plug.

Refer to the wiring diagram. What leads you to think e-start was ever installed?

[JDT]

If the jumper is not in place no lights will work at all.
Nor the tach if one is present.

[kreechur]

Thanks guys, I found the connector last night, and there is a jumper wire in there, so that must not be the issue... Time to trace grounds i guess...