Pulsating and Dimming Dash Lights
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Intermediate
Joined: Mar 2012
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From: Virginia
Pulsating and Dimming Dash Lights
1987 FLHTC
When the bike is idling the dashlights pulsate, the more throttle and revs, the dimmer the dashlight become all while the pulsating continues. At 100MPH, the dashlights are just about out.
Headlight and taillights are rock solid. I thought it was the voltage regulator rectifier and\or the alternator so I swapped it out with a new
Compu-Fire 3 Phase Charging System. Did not help that problem, but at least I got good juice back to the battery at all times, which happened to be the real reason for the new charging system.
Anyone else ever run into this?
When the bike is idling the dashlights pulsate, the more throttle and revs, the dimmer the dashlight become all while the pulsating continues. At 100MPH, the dashlights are just about out.
Headlight and taillights are rock solid. I thought it was the voltage regulator rectifier and\or the alternator so I swapped it out with a new
Compu-Fire 3 Phase Charging System. Did not help that problem, but at least I got good juice back to the battery at all times, which happened to be the real reason for the new charging system.
Anyone else ever run into this?
Last edited by Summers420us; Jun 12, 2012 at 09:15 AM.
Seasoned HDF Member
Joined: Aug 2007
Posts: 8,195
Likes: 3,085
From: NW AR
If your charging system is functioning properly, and it is all of your dash lights, not just 1, then I would suspect a bad ground. There is a whole ground block under the faring. Take it apart and clean everything. You could also test my hypothesis by putting a clip lead on the battery negative terminal and running it to the ground block under the dash and seeing if it still does it. The other thing would be to track down where the dash lights take power off the switched line and make sure that is clean. And check the start relay under the oil tank cover. If that has dirty contacts, that could do it as well. There are probably some other points as well, but try that first and if it doesn't clear it up, I'll dig out my schematics and see if I can narrow it down better. Our bikes should be wired just about the same.
I guess I don't have to tell you to properly diagnose problems before spending $$$$ throwing parts at a problem. But I hear those 3 phase systems are good and you probably needed to upgrade the 22 amp system in there anyway.
I guess I don't have to tell you to properly diagnose problems before spending $$$$ throwing parts at a problem. But I hear those 3 phase systems are good and you probably needed to upgrade the 22 amp system in there anyway.
Thread Starter
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Intermediate
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From: Virginia
Yep, I like the 3 phase system. Money well spent for me in this case.
Seasoned HDF Member
Joined: Aug 2007
Posts: 8,195
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From: NW AR
You, you have to remove the outer fairing to get to the block. Maybe the radio too, but I don't remember exactly on that. You should see a block with a half dozen or so black wires going to it with spade connectors. That's it. You might be able to see it with just the headlight bucket pulled, and you could probably run a clip lead to it at that stage.
As for the relay, it is only like $5-10 at any auto parts store and is a wear item. You could check the voltage on both sides of the normally closed contacts and see if there is a difference or just replace it.
Hint: If you get a 7/16" gear wrench, it only takes 5 or 10 minutes to pull the outer fairing.
As for the relay, it is only like $5-10 at any auto parts store and is a wear item. You could check the voltage on both sides of the normally closed contacts and see if there is a difference or just replace it.
Hint: If you get a 7/16" gear wrench, it only takes 5 or 10 minutes to pull the outer fairing.
Thread Starter
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Intermediate
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From: Virginia
I don't mind take a $5 or $10 dollar gamble on a wear item. I will give that a shot.
This is the relay you speak of right?
OEM 31506-79B/C
Bosch AC40116
So, current to the dash lighs, goes through here? I am amazed that current other than that used for energizing the starter solenoid goes through here. Who would've thunk it? Is there another path through this unit for the dash lights?
Starter works great by the way.
This is the relay you speak of right?
OEM 31506-79B/C
Bosch AC40116
So, current to the dash lighs, goes through here? I am amazed that current other than that used for energizing the starter solenoid goes through here. Who would've thunk it? Is there another path through this unit for the dash lights?
Starter works great by the way.
Seasoned HDF Member
Joined: Aug 2007
Posts: 8,195
Likes: 3,085
From: NW AR
That's what the relay looks like. I don't know about that exact part number, but I'd say that was it.
Yeah, the current for the whole bike, basically, goes through that relay, then back up to the dash. It is switched "off" when you hit the starter button by that relay, and the circuit goes to the solenoid instead. There's like a dozen connections between the battery and the solenoid, including that relay. So, yeah, there's a chance that a dirty normally closed contact inside that relay could be causing your problems. If I recall, it's the Orange wire and it's called "accessory."
Ideally, you should get the schematic out, a DVM, and start at the dash light and work your way back until you get good, solid 13v with the bike running. You will eventually find the dirty contact or be back at the battery, but it is not that simple to do, finding every side of every connection and wire. That's what I did to find the root cause/solution of The Dreaded Click, which turned out to be pretty much all of the dozen connections adding a little bit of resistance at each point, from my analysis.
Yeah, the current for the whole bike, basically, goes through that relay, then back up to the dash. It is switched "off" when you hit the starter button by that relay, and the circuit goes to the solenoid instead. There's like a dozen connections between the battery and the solenoid, including that relay. So, yeah, there's a chance that a dirty normally closed contact inside that relay could be causing your problems. If I recall, it's the Orange wire and it's called "accessory."
Ideally, you should get the schematic out, a DVM, and start at the dash light and work your way back until you get good, solid 13v with the bike running. You will eventually find the dirty contact or be back at the battery, but it is not that simple to do, finding every side of every connection and wire. That's what I did to find the root cause/solution of The Dreaded Click, which turned out to be pretty much all of the dozen connections adding a little bit of resistance at each point, from my analysis.
Road Warrior
Joined: Oct 2011
Posts: 1,376
Likes: 36
From: Round Rock, TX
I had the same, but opposite problem. (See the Dimming headlight thread). Everything in the front *but* the dash lights were dimming. It was indeed a ground.
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Intermediate
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From: Virginia
It will be a bit before I can check these things. I have been called away for a week or so, but as soon as I can, I will post my findings. Thanks for all your help.
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Thread Starter
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Intermediate
Joined: Mar 2012
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From: Virginia
Replaced the solenoid, but that did not fix it. Ran another ground wire from a free spot on the ground block behind the outer fairing to the right of the radio and deep, to a screw that holds a wire guide to the neck of the frame on the right side of the bike. So far so good, but only time will tell if it really solved my problem.
Road Captain
Joined: May 2011
Posts: 684
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From: Indian Head, PA
Ever since I got my bike, I noticed that the dash lights as well as the gauge lights in the fairing would dim with the turn signals or the brake light. The volt gauge would also jump up and down in time with the signals. RPM doesn't seem to have any effect as it does it whether idling or revved up. I don't know if it's normal or not, but this thread got me to thinking that maybe it's not normal.
So tonight I went out to the garage and pulled out the headlight bucket to look for the ground block. I didn't find the ground block, it must be in the dash on top of the triple clamp. I did however see how the grounds for the radio and cig lighter socket went to the lower bolt of the two that attach the back of the fairing to the front end of the frame, while the grounds for the headlights and the gauges each have their own connector in the multi-post pass-through back to the dash.
I simply exposed one of the ground wires(the one from the voltage gauge) where it passes next to the lower bolt to the frame(where the radio/cig lighter grounds are), crimped on a new ring terminal and added it to the bolt, basically "doubling up" the ground for the gauges.
On testing it, a new potential problem popped up. The lights still dim and the volt gauge still jumps with the signals or brake light. But after using the turn signals for a few seconds, then trying the brakes, lighting up the brake light, the turn signals would not work at all. I started the engine and it turned over a little slower than normal, but still fired right up, and the signals were back. I am wondering if perhaps not enough voltage is getting through or if I really need to find the dash ground block and clean it up. The battery voltage is plenty, the battery is good, has been tested and passed, plus it's barely a year old.
Should I maybe look at the original start relay? I haven't replaced it yet. Main circuit breaker?
So tonight I went out to the garage and pulled out the headlight bucket to look for the ground block. I didn't find the ground block, it must be in the dash on top of the triple clamp. I did however see how the grounds for the radio and cig lighter socket went to the lower bolt of the two that attach the back of the fairing to the front end of the frame, while the grounds for the headlights and the gauges each have their own connector in the multi-post pass-through back to the dash.
I simply exposed one of the ground wires(the one from the voltage gauge) where it passes next to the lower bolt to the frame(where the radio/cig lighter grounds are), crimped on a new ring terminal and added it to the bolt, basically "doubling up" the ground for the gauges.
On testing it, a new potential problem popped up. The lights still dim and the volt gauge still jumps with the signals or brake light. But after using the turn signals for a few seconds, then trying the brakes, lighting up the brake light, the turn signals would not work at all. I started the engine and it turned over a little slower than normal, but still fired right up, and the signals were back. I am wondering if perhaps not enough voltage is getting through or if I really need to find the dash ground block and clean it up. The battery voltage is plenty, the battery is good, has been tested and passed, plus it's barely a year old.
Should I maybe look at the original start relay? I haven't replaced it yet. Main circuit breaker?