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1983 Bombi charging system troubleshooting

Mustang

New member
I have a 1983 project Bombi I bought a couple of years ago that I’m putting the finishing touches on. I’m currently trying to solve a charging system issue and could use an assist.
The machine has the 60 amp alternator option which uses a Standard Motor Products external voltage regulator with the original Ford industrial 1.6 liter engine. The specific issue I’m having is with the alternator light on the dash.
The original alternator dash light was trashed so I replaced it with a 12 volt LED indicator light. The LED light comes on when I turn the key as it should, but it stays on when the engine has been started and is running. The alternator light is supposed to turn off once the engine starts. The voltage regulator seems to be doing its job. At the battery I’m measuring about 14.5 volts with the engine running. Maybe that voltage is too high?
Thinking that the voltage regulator was doing its job and an old school incandescent lamp might be what was needed, I removed the LED light and replaced it with a 12 volt incandescent lamp. The weird thing is the old school incandescent lamp does not come on at all with just the key. It also doesn’t come on when the engine is running either. The alternator’s still happy and charging as it should be with the incandescent that doesn’t light up. Without the LED or incandescent lamp the alternator doesn’t work since having a lamp is needed to close the “I” circuit of the voltage regulator in the charging system.
To trouble shoot I checked the incandescent lamp to make sure it wasn’t burned out. It comes on just fine when I hook it up to a 9 or 12 volt battery. So now back to the cat. When I turn the ignition key to the “on” position, I measure battery voltage in the bulb socket at 12.5 volts.
So the mystery is why does the LED light come on and the incandescent one not? Why doesn’t the LED light go off when the engine is running? I’ve checked all the wiring and grounds with a multi meter. Everything checks out with the wiring. I’ve also pulled out the alternator and had it checked at two different auto parts shops. The alternator checks out fine. So now I’m down to the voltage regulator.
The guys who checked the alternator don’t have a way to check the external voltage regulator and there are no part numbers to be found anywhere on it. The only markings on it are the brand “Standard Motor Products”. Does anyone have a part number for the Bombi Standard Motor Products voltage regulator that’s used with a 60 amp alternator and Ford 1.6 liter engine? Does anyone have a recommendation on a modern compatible internally regulated alternator and associated schematic that I could replace the existing system with? Is 14.5 volts at the battery too high a voltage to be recharging the battery with?
Thanks for reading and for any suggestions you may have!
 

MNoutdoors RIP

Gone But Not Forgotten
GOLD Site Supporter
I have a 1983 project Bombi I bought a couple of years ago that I’m putting the finishing touches on. I’m currently trying to solve a charging system issue and could use an assist.
The machine has the 60 amp alternator option which uses a Standard Motor Products external voltage regulator with the original Ford industrial 1.6 liter engine. The specific issue I’m having is with the alternator light on the dash.
The original alternator dash light was trashed so I replaced it with a 12 volt LED indicator light. The LED light comes on when I turn the key as it should, but it stays on when the engine has been started and is running. The alternator light is supposed to turn off once the engine starts. The voltage regulator seems to be doing its job. At the battery I’m measuring about 14.5 volts with the engine running. Maybe that voltage is too high?
Thinking that the voltage regulator was doing its job and an old school incandescent lamp might be what was needed, I removed the LED light and replaced it with a 12 volt incandescent lamp. The weird thing is the old school incandescent lamp does not come on at all with just the key. It also doesn’t come on when the engine is running either. The alternator’s still happy and charging as it should be with the incandescent that doesn’t light up. Without the LED or incandescent lamp the alternator doesn’t work since having a lamp is needed to close the “I” circuit of the voltage regulator in the charging system.
To trouble shoot I checked the incandescent lamp to make sure it wasn’t burned out. It comes on just fine when I hook it up to a 9 or 12 volt battery. So now back to the cat. When I turn the ignition key to the “on” position, I measure battery voltage in the bulb socket at 12.5 volts.
So the mystery is why does the LED light come on and the incandescent one not? Why doesn’t the LED light go off when the engine is running? I’ve checked all the wiring and grounds with a multi meter. Everything checks out with the wiring. I’ve also pulled out the alternator and had it checked at two different auto parts shops. The alternator checks out fine. So now I’m down to the voltage regulator.
The guys who checked the alternator don’t have a way to check the external voltage regulator and there are no part numbers to be found anywhere on it. The only markings on it are the brand “Standard Motor Products”. Does anyone have a part number for the Bombi Standard Motor Products voltage regulator that’s used with a 60 amp alternator and Ford 1.6 liter engine? Does anyone have a recommendation on a modern compatible internally regulated alternator and associated schematic that I could replace the existing system with? Is 14.5 volts at the battery too high a voltage to be recharging the battery with?
Thanks for reading and for any suggestions you may have!


I personally like a volt gage that shows me what I have for voltage all the time off,running or charging, I do not believe the LED light is going to work the circuit needs the little bit of resistance the normal bulb with have to work. The LED is a diode and only allows power to flow in one direction. 14.5 is a good charge voltage if the battery is low if it's fully charged you would hope it would drop down a bit.
 

rcc

Member
In my work with these the proper bulb is used as a resistor, telling the alt to start gen'ing power to charge as you mentioned, so a LED will not give the proper resistance. On my BR100+ the Alt light does not come on unless the charging circuit is not working. 14.5 V charging is not to high, it is normal. All my machines and new vehicles including the Audi R8 runs at 14.5 when running.
 

MNoutdoors RIP

Gone But Not Forgotten
GOLD Site Supporter
Did find this

I used an LED and wired a 470 ohm resistor in parallel to match the factory arrangement. It has worked fine for 5 years now.

The alternator uses the voltage from the warning light circuit as a signal to turn on and start charging. I don't know for sure, but an LED by itself may not provide enough current for this to happen.
 

rcc

Member
Ford and other car mfg'rs used a oem light bulb for years to for this purpose. I looked it up to rewire my J5 10 years or more ago. But glad to know I can use the LED and a 470 resistor, as I see it the old bulbs will be gone sooner than we think... who know how long they will let the resistor live............!?
 

Mustang

New member
First, thank you very much Boggie and RCC for your replies! This forum is really amazing!!! Your comments and suggestions are really helpful.

The machine is up on the mountain at the cabin so I’ll take some resistors up with me this weekend and see if I can get the alternator light to go off.
When I began having charging system issues, I added a voltage gauge to the instrument cluster so I could see how things were charging. That’s been helpful. With the Pertronix Ingitor II solid state ignition I installed, if there’s not a constant 12 volts for the ignition, the fun is over!
I’ll let you guys know how things turn out this weekend.
Thanks again!
 

rcc

Member
Thought I mentioned it before but, Pertronics has a relay just for that purpose of keeping as much voltage provided to the coil. That way the coil doesn't see any voltage drop when you turn on lights etc.
 

Mustang

New member
That's really good information to have. Thanks for the recommendation. Are you running a solid state ignition with one of these relays?
 

rcc

Member
I have Pertronix ingnitor systems in 2 J5's, works perfect and both have the Pertronix relay setup.

I also put the headlamps on a relay, no more dimming or brown out.
 

JimVT

Bronze Member
GOLD Site Supporter
the pertronics with the resister in the circuit worked fine the 3 years I run my stock bombi. tech at pertroncics said it will work with or without.
 

Mustang

New member
Here's the weekend report. The 470 ohm resistor wired in parallel with the 12 volt LED indicator light didn't work out. The LED wouldn't come on with the resistor in parallel - resistor checked out fine with multimeter. I'm obviously not getting the resistive load just right.
With just the LED back in the circuit, I lived with the light staying on, watched the volt meter closely, and just played in the snow! The cat ran great with the Petronix ignition and coil set up and the alternator and voltage regulator played nice too. I'm going add the suggested relay in the near future. That's the right thing to do.
I'm not giving on the alternator light yet. I have the OEM alternator light part number. The part's obsolete but I will call the manufacturer to get some specs and figure out an equivalent set up. Beyond that, we could use some snow out here in the Rocky Mountains. It's like spring out here.
 

MNoutdoors RIP

Gone But Not Forgotten
GOLD Site Supporter
Here's the weekend report. The 470 ohm resistor wired in parallel with the 12 volt LED indicator light didn't work out. The LED wouldn't come on with the resistor in parallel - resistor checked out fine with multimeter. I'm obviously not getting the resistive load just right.
With just the LED back in the circuit, I lived with the light staying on, watched the volt meter closely, and just played in the snow! The cat ran great with the Petronix ignition and coil set up and the alternator and voltage regulator played nice too. I'm going add the suggested relay in the near future. That's the right thing to do.
I'm not giving on the alternator light yet. I have the OEM alternator light part number. The part's obsolete but I will call the manufacturer to get some specs and figure out an equivalent set up. Beyond that, we could use some snow out here in the Rocky Mountains. It's like spring out here.


Ohm resistance may vary based on your alternator also make sure your diode is in the correct polarity

There are several articles if you google replacing idot light with led
 
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