1980 C70 Passport, headlight and wiring issues

Dan Stephens

New Member
I have a 1980 C70 Passport that keeps blowing headlights. From reading elsewhere here I see that it is probably my voltage regulator blowing the bulbs. It gets brighter and more dim as you accelerate/brake. Here are a couple of other issues I’m having with the headlamp/ electrical system.
Since each NOS bulb is $43 and 3 weeks to get it here. Here are my 2 questions,
1. Why would the headlamp and taillight flash with the blinkers now that the bulb is replaced?
(I’ve downloaded a wiring schematic to make sure I reinstalled the wires correctly. Everything looks right in the headlight cavity.)
2. Would it be possible to install a 6v LED into the system if I can find a headlight assembly that takes insert bulbs instead of a whole headlamp?
 
I have a 1980 C70 Passport that keeps blowing headlights. From reading elsewhere here I see that it is probably my voltage regulator blowing the bulbs. It gets brighter and more dim as you accelerate/brake. Here are a couple of other issues I’m having with the headlamp/ electrical system.
Since each NOS bulb is $43 and 3 weeks to get it here. Here are my 2 questions,
1. Why would the headlamp and taillight flash with the blinkers now that the bulb is replaced?
(I’ve downloaded a wiring schematic to make sure I reinstalled the wires correctly. Everything looks right in the headlight cavity.)
2. Would it be possible to install a 6v LED into the system if I can find a headlight assembly that takes insert bulbs instead of a whole headlamp?
My guess is your battery needs replacing. If your battery is good, I suspect your voltage regulator/rectifier. The charging system charges your battery, but if your battery can't accept the additional juice, it'll start blowing bulbs. One trick you can try is to take one of your blown headlights and with a dremel, cut a hole so that a universal automotive double contact tail light recepticle can be inserted in the hole. Then just use a 6 volt tailight bulb as a headlight. If it blows, you're only out a couple of bucks. I did this to my neighbor's CT110 and used a 12 volt LED tailight bulb which will never blow and is still pretty bright even at 6 volts. Using your wiring diagram, try tracing the turn signal wiring, especially the rear, as well as the tailights, verifiying the green wires (grounds) are all good.
 

-Nate

Member
As mentioned, your C70 has NO VOLTAGE REGULATOR ~ it has a rectifier and the battery stabilizes the charging voltage .

Most newer batteries are Tianwanese crap , the venerable CT110 has the same headlight blowing issue, try to get a Japanese made battery before anything else .

Many have done the aforementioned cutting out of a dead seal beam and inserting a regular 6 volt 25 watt CT200 headlight bulb .

If the headlight is blinking with the turn signals you have a serious problem there, sounds like a ground issue to be, some years don't have a (green) ground wire leading from the headlight / front fork to the frame, the ball bearings in the steering stem carry to current load and can't after many decades, easy enough to add an 18 gauge green wire from the 10MM ATF bolt that holds the headlight ground and run it back to the engine proper .

FWIW, the alternator easily puts out 20 VDC when unregulated so having a good battery is critical here .


Some times the MPC connectors inside he frame cavity behind the battery get corroded, *gently* take it apart and peer inside ~ if you see any greenish fuzz, there's your problem .

In ay case I'd replace or upgrade the rectifier as even the late model potted epoxy ones have a life span .

Pardue Brothers in Florida sell plug and play new upgraded rectifiers that are far better than the factory Honda part .

Also, try Beatrice Cycle, AKA : DRATV for lots of parts for your bike~ he's CT90/110 oriented but also knows and has parts for Passports, CL90s and other older Honda Tiddlers, Jack is a very good guy and honest as the day is long .

Let us know what you find .
 

Dan Stephens

New Member
As mentioned, your C70 has NO VOLTAGE REGULATOR ~ it has a rectifier and the battery stabilizes the charging voltage .

Most newer batteries are Tianwanese crap , the venerable CT110 has the same headlight blowing issue, try to get a Japanese made battery before anything else .

Many have done the aforementioned cutting out of a dead seal beam and inserting a regular 6 volt 25 watt CT200 headlight bulb .

If the headlight is blinking with the turn signals you have a serious problem there, sounds like a ground issue to be, some years don't have a (green) ground wire leading from the headlight / front fork to the frame, the ball bearings in the steering stem carry to current load and can't after many decades, easy enough to add an 18 gauge green wire from the 10MM ATF bolt that holds the headlight ground and run it back to the engine proper .

FWIW, the alternator easily puts out 20 VDC when unregulated so having a good battery is critical here .


Some times the MPC connectors inside he frame cavity behind the battery get corroded, *gently* take it apart and peer inside ~ if you see any greenish fuzz, there's your problem .

In ay case I'd replace or upgrade the rectifier as even the late model potted epoxy ones have a life span .

Pardue Brothers in Florida sell plug and play new upgraded rectifiers that are far better than the factory Honda part .

Also, try Beatrice Cycle, AKA : DRATV for lots of parts for your bike~ he's CT90/110 oriented but also knows and has parts for Passports, CL90s and other older Honda Tiddlers, Jack is a very good guy and honest as the day is long .

Let us know what you find .


So after going through the wiring harness I figured out it was the after market headlight assembly that was the issue. It was plastic, therefore not grounding to the frame. Took the advice above and cut out the back of an old bulb. Now has a bulb assembly inserted with an 1154 bulb. This also fixed the ground issue. Last, the battery was the problem with the headlight blowing, installed a new battery and replaced the rectifier. All good to go again. Thanks so much everyone!
 

Dan Stephens

New Member
So after going through the wiring harness I figured out it was the after market headlight assembly that was the issue. It was plastic, therefore not grounding to the frame. Took the advice above and cut out the back of an old bulb. Now has a bulb assembly inserted with an 1154 bulb. This also fixed the ground issue. Last, the battery was the problem with the headlight blowing, installed a new battery and replaced the rectifier. All good to go again. Thanks so much everyone!
 

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-Nate

Member
That's good to hear .

I'd like you to please post an imamge of the bad plastic item, many of them are poor Chinese copies and there's an available Honda factory part that fits the Chinese lens reflector and ring assembly .

A #1154 bulb is a two filament brake and running lamb bulb, I hope you're not going to ride at night with that headlight as it's dangerously dim .
 

Dan Stephens

New Member
Which is why the plastic setup wouldn’t work correctly. Wondering if you ran a ground from the internal ring to the outer if that would work on the plastic one.
 

Dan Stephens

New Member
One other thing with the knock off part, you had to use the bottom right screw hole instead of the top right one when installing. Part not recommended, the old bulb modification is best route.
 

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Dan Stephens

New Member
Last step is to swap out the 1154 bulb for a much brighter LED. Was using the 1154 bulb to check if the modifications went as planned. New bulb should arrive this week 🙂
 

-Nate

Member
O.K., the original bulb holder has three wires, the green one is the ground path and cannot be connected to any part of the headlight assembly to work properly .

The white wire is the high beam, the blue wires is the low beam .

I'm sure there's a scooter LED headlight you can adapt, mind it's directional and needs one way up only .

I have to go to work, I am following this thread and will give any help I can .

I'd like to get the defective bulb holder in my hands .
 
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