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Author Topic: Dim headlight demon  (Read 1789 times)

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Offline Bigbondo007

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Dim headlight demon
« on: January 02, 2019, 05:00:36 PM »
76cb750a, sylvania 40/60 bulb, 340cca agm battery, new dyna s. The headlight is pretty dim, no change with rpm increase. At high idle I have 12.3v at the battery, 10.5v at the fuse and 9v at the headlight. The bike has no starting issues after long or short rides. Just wondering if these were common values and what possible remedies can I look at?

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« Last Edit: January 02, 2019, 05:04:21 PM by Bigbondo007 »
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Offline Bankerdanny

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Re: Dim headlight demon
« Reply #1 on: January 02, 2019, 09:05:17 PM »
You need to put it in neutral and rev the engine to test for peak voltage.

However, based on the voltage drops across the various locations I would be cleaning connections and checking out the connections inside the left bar control where the high/low switch is.
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Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline Bigbondo007

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Re: Dim headlight demon
« Reply #2 on: January 02, 2019, 09:26:21 PM »
Quote from: Bankerdanny on January 02, 2019, 09:05:17 PM
You need to put it in neutral and rev the engine to test for peak voltage.

However, based on the voltage drops across the various locations I would be cleaning connections and checking out the connections inside the left bar control where the high/low switch is.
I'll check all the connections again tomorrow.

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Offline Deltarider

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Re: Dim headlight demon
« Reply #3 on: January 02, 2019, 11:51:35 PM »
Start with the connections to Ground, in particular in the headlamp.
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Offline bryanj

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Re: Dim headlight demon
« Reply #4 on: January 03, 2019, 04:44:17 AM »
Those voltages are all very low
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Offline przjohn

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Re: Dim headlight demon
« Reply #5 on: January 03, 2019, 05:38:34 AM »
There is a bad connection somewhere, that is not normal. Looks like you may have multiple bad connections with your fuse reading and HL reading. Was the wiring harness modified to accept the fairing? That would be a suspect spot, but I wouldn't hopscotch around and just take it step by step through the connections and  would start right at the battery, and then to the fuse box and so on. As has been stated check your grounding also.
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Offline Bigbondo007

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Re: Dim headlight demon
« Reply #6 on: January 03, 2019, 05:51:34 AM »
Quote from: przjohn on January 03, 2019, 05:38:34 AM
There is a bad connection somewhere, that is not normal. Looks like you may have multiple bad connections with your fuse reading and HL reading. Was the wiring harness modified to accept the fairing? That would be a suspect spot, but I wouldn't hopscotch around and just take it step by step through the connections and  would start right at the battery, and then to the fuse box and so on. As has been stated check your grounding also.
The fairing harness is plug and play, assuming you have the vetter wiring diagram as I do. Nothing  has been modified. The bike is a true barn find.

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Offline przjohn

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Re: Dim headlight demon
« Reply #7 on: January 03, 2019, 06:07:11 AM »
Quote from: Bigbondo007 on January 03, 2019, 05:51:34 AM
Quote from: przjohn on January 03, 2019, 05:38:34 AM
There is a bad connection somewhere, that is not normal. Looks like you may have multiple bad connections with your fuse reading and HL reading. Was the wiring harness modified to accept the fairing? That would be a suspect spot, but I wouldn't hopscotch around and just take it step by step through the connections and  would start right at the battery, and then to the fuse box and so on. As has been stated check your grounding also.
The fairing harness is plug and play, assuming you have the vetter wiring diagram as I do. Nothing  has been modified. The bike is a true barn find.

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Even plug and play can have corrosion issues. I have seen plugs that have never been touched outside of the factory not making a circuit. Wiggle it a bit and, Wa-La power restored. Old motorcycles and boats are notorious for bad connections due to corrosion. Lots of guys who do restorations will replace the harness if available or replace every connector. I realize that is most likely not an option but if you just go through and clean them up I bet you solve the problem. You can also buy new connectors at vintage connections that work great.
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Offline Bigbondo007

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Re: Dim headlight demon
« Reply #8 on: January 03, 2019, 06:08:46 AM »
I'm going to go through the entire harness in a few minutes

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Offline Bigbondo007

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Re: Dim headlight demon
« Reply #9 on: January 03, 2019, 06:34:59 AM »
Quote from: przjohn on January 03, 2019, 06:07:11 AM
Quote from: Bigbondo007 on January 03, 2019, 05:51:34 AM
Quote from: przjohn on January 03, 2019, 05:38:34 AM
There is a bad connection somewhere, that is not normal. Looks like you may have multiple bad connections with your fuse reading and HL reading. Was the wiring harness modified to accept the fairing? That would be a suspect spot, but I wouldn't hopscotch around and just take it step by step through the connections and  would start right at the battery, and then to the fuse box and so on. As has been stated check your grounding also.
The fairing harness is plug and play, assuming you have the vetter wiring diagram as I do. Nothing  has been modified. The bike is a true barn find.

Sent from my SM-N950U using Tapatalk

Even plug and play can have corrosion issues. I have seen plugs that have never been touched outside of the factory not making a circuit. Wiggle it a bit and, Wa-La power restored. Old motorcycles and boats are notorious for bad connections due to corrosion. Lots of guys who do restorations will replace the harness if available or replace every connector. I realize that is most likely not an option but if you just go through and clean them up I bet you solve the problem. You can also buy new connectors at vintage connections that work great.
Haha, OK with the fairing removed I have 13.2 at idle and 15.2 at high rev

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Offline Bigbondo007

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Re: Dim headlight demon
« Reply #10 on: January 03, 2019, 08:37:35 AM »
Ok, I took the fairing off and went through the front wiring harness per the factory manual. Made a few few corrections to the vetter harness and connected everything back. At 1/4-1/3 throttle i have 13.5 at the battery. At the headlight connector I get 12.5 disconnected and 9.5 connected. I'm running a SYLVANIA H6024 2D1 SilverStar High Performance Halogen Headlight 7" Round 40/60w



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Offline Bigbondo007

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Re: Dim headlight demon
« Reply #11 on: January 03, 2019, 08:51:21 AM »
I'm tempted to take the 50/55w h4 out of the road king and try it

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Offline Bankerdanny

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Re: Dim headlight demon
« Reply #12 on: January 03, 2019, 09:27:40 AM »
The headlight rating is draw, it shouldn't produce low power ratings at the connector. Based on what you are seeing with and without the faring it would seem like the internal wiring between the plug and the headlight bucket is an issue.
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Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline Bigbondo007

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Re: Dim headlight demon
« Reply #13 on: January 03, 2019, 09:58:05 AM »
Quote from: Bankerdanny on January 03, 2019, 09:27:40 AM
The headlight rating is draw, it shouldn't produce low power ratings at the connector. Based on what you are seeing with and without the faring it would seem like the internal wiring between the plug and the headlight bucket is an issue.
Ok, just bypassed the fairing by removing the headlamp and connecting back to the original harness. No change from previous.

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Offline Bigbondo007

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Re: Dim headlight demon
« Reply #14 on: January 03, 2019, 10:33:34 AM »
I'm about to fix this problem though

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Offline Bigbondo007

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Re: Dim headlight demon
« Reply #15 on: January 03, 2019, 11:32:27 AM »
Ive used these harnesses in the past and never had any issues. The relay is rated for 40A and the fuse for 30A. All the connections are solid and it comes weatherproofed. Looks very much like a atv/cycle factory harness. $10 at Wal-Mart, more at the parts store. &

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Offline bryanj

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Re: Dim headlight demon
« Reply #16 on: January 03, 2019, 12:18:38 PM »
If the volts drop that much with just the headlamp added either battery or generator are duff
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Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline Bigbondo007

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Re: Dim headlight demon
« Reply #17 on: January 03, 2019, 12:31:58 PM »
Quote from: bryanj on January 03, 2019, 12:18:38 PM
If the volts drop that much with just the headlamp added either battery or generator are duff
There's no drop in the voltage to the battery, it stays relatively the same. The drop is at the lamp

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Offline Bigbondo007

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Re: Dim headlight demon
« Reply #18 on: January 03, 2019, 01:12:41 PM »
Quote from: bryanj on January 03, 2019, 12:18:38 PM
If the volts drop that much with just the headlamp added either battery or generator are duff
New harnesses and relays installed, 13.5v at the headlamp at 1/4 throttle.

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Offline Bigbondo007

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Re: Dim headlight demon
« Reply #19 on: January 03, 2019, 06:23:00 PM »
Tested in pitch black down the road and it's actually better than my Harley. Should have done the relay conversion earlier.

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