within one volt above or under battery voltage
The head lamps should not get dim. Dim light are an indication of low voltage. You should have a volt meter in the instrument panel. If the voltages is not reading about 14V when the engine is running, you have a bad battery or alternator. It should read over 12V with the engine not running and the ignition in the on position. It should not drop below about 9-10 when cranking the engine. If you have low voltage during cranking and normal voltage at other times, you probably need to replace the battery.
In my experience you must have voltage to the coil...it must be energized to sustain the engine current to work properly. this requires to have current from the ignition to the engine system. If there is no signs of current-voltage with the ignition ON - more likely it is interrupted at the switch. You may trace continuity on wires from the coil to the switch. check the fuse block to insure that no fuses are bad. You may fing a book on the used books store and locate the diagrams...you may search the net...they are there....keep an eye in the color code to ID the wires -they go from the engine compartment to the inside of the unit...I am assuming the that engine is not running. I am in Texas.
12 VOLTS
If you are checking Alternator voltage, It should 12.8 volts to 14.3 with engine running. Battery voltage is 12.3---12.8 with engine off.
To test the glow plug controller on a 6.5L diesel engine, begin by ensuring the engine is off and the ignition is in the "off" position. Use a multimeter to check for voltage at the glow plug controller terminals while turning the ignition key to the "on" position; you should see voltage indicating the controller is functioning. Additionally, inspect the controller for any visible signs of damage or corrosion. If the voltage is absent or the controller appears faulty, it may need to be replaced.
The check engine light is just to the left of your battery voltage gauge in your gauge cluster . When you turn your ignition key to the run position , just before starting your engine , the check engine light should come on momentarily to check the bulb
To jump start an engine via the battery; the remote battery and the host battery, being of the same voltage, should be connected in parallel. That is positive terminal to positive terminal, negative to negative.
"Check Engine" light comes on when you turn ignition switch on and should go off when engine cranks.
when ignition is on it should be battery volts,when cranking in should pulse..(test with a led test light or osilliscope
On fuel injected models, the Engine Control Module regulates voltage. On carbureted models the voltage regulator should be mounted on the firewall near the ignition coil. It should look like a small metal box about the size of a pack of cigarettes and be held on by two small bolts and have a small wiring harness (two or maybe three wires).
10 btdc
The ignition coil is down between the firewall and the back of the engine