Backfires

I have a 4020 gas. Alternator went out so I replaced it. I have 4 headlamps on front of fenders. When I turn lights on it backfires and dies. If I run without lights it works fine. Can't find a short. Any ideas?

First thing I would check is battery voltage not running which is 12 volts should be around 12.5 volt plus. Then when running should be around 13.5-15 volts. Then turn non the lights while you have the volt meter hooked up and see what it reads. As for finding a short one of the bulbs could have a short in it

several thoughts..

either headlights are shorted, or drawing way too much power, so that the voltage drops so low, the coil can no longer produce enough spark and it dies.

This could also mean the alternator is NOT working and the battery barely has enough charge to barely run the coil at about 2 to 3 amps of load.. as soon as the 10 amps of lights come on, the battery gives up the ghost and the engine dies.

if its 12 volts, jump with from a car with good cables and retest... the car supplying the extra power should fix the problem... and the car if running, will try to charge up your mostly dead battery or provide enough power to run it. this will eliminate a low/ nearly dead battery.


also could be a very bad connection between battery and system .. in the run circuit... so the add on of the headlights will lower the voltage going to the coil, but not affect the starting circuit as it routes differently from the ignition switch to the starter solenoid.. so on that premise, look at the ignition switch down to the coil... assuming the crank circuit runs through the ig switch and works well.

I am assuming if it cranks good, then the battery must be sound.

Possible you have a loose connection sending power to your switch or a bad
switch. Time to get voltmeter out and start troubleshooting.

Try removing the power wire going to lights from switch and wire it directly
to battery. If your problem goes away, bad connection or bad switch.
If problem persists, bad charging system. Alternator will have to produce
more than 13.6 v to charge battery, so expect to see a running voltage from
alternator in the 13-14.5 volt range.

Many YT people love their old resister load tester. I love my digital tester,
I have a lot of confidence in it. It has clamp on leads, so it very easy for
me to see how many amps battery can produce without draining and check
alternator voltage, hands free. You may want to find alligator clips for your
voltmeter leads.

Have fun find the gremlin.
geo
geo

(quoted from post at 07:07:19 01/13/17) Possible you have a loose connection sending power to your switch or a bad
switch. Time to get voltmeter out and start troubleshooting.

Try removing the power wire going to lights from switch and wire it directly
to battery. If your problem goes away, bad connection or bad switch.
If problem persists, bad charging system. Alternator will have to produce
more than 13.6 v to charge battery, so expect to see a running voltage from
alternator in the 13-14.5 volt range.

Many YT people love their old resister load tester. I love my digital tester,
I have a lot of confidence in it. It has clamp on leads, so it very easy for
me to see how many amps battery can produce without draining and check
alternator voltage, hands free. You may want to find alligator clips for your
voltmeter leads.

Have fun find the gremlin.
geo
geo

Click to expand...

I will give it a try. I appreciate all your help.

Does this happen as soon as the lights are turned on?

If so, somehow the lights are drawing power away from the ignition circuit. Possibly a bad connection between the battery and the ignition switch, the ampmeter, the light switch, etc. Look for signs of corrosion or heat damaged insulation. If you have a volt meter, start checking connections with the lights and ignition on. That way the system will be under load.

If this happens after running for a while, and the lights slowly grow dim, and the battery discharges, there is a problem with the charging system. could be a defective or too low amp alternator, loose belt, bad wiring connection.