Brake lt woes

Patton wrote:

mark1122 wrote:

...dont get a flashing, warning, when the bulb element is out, only if i remove the bulb?

Flashing is warning only about functionality of brake light, not running (tail) light function.

If the rear bulb's running light filament is blown (such as riding along at night without a taillight), but the brake light comes on when brake is applied, there is no flashing warning.

If the rear bulb is removed, the flashing warning is saying the brake light won't come on when the brake is applied. Same as flashing warning when the installed rear bulb's brake light filament is blown.

The flashing warning system doesn't give a hoot about the rear running light. And only cares about functionality of the brake light.

Good Fortune!

Funny how it all makes perfect sense, when someone that knows what they are talking about , explains it.:laugh:
Thanks again Patton.

Motor Head wrote:

The reason for the big change in voltage when you un plug the head light is that you have taken the current draw of about 4.5 AMPs out of the circuitry. If you had good connections and wiring able to handle this the voltage drop would be minimal.

i just rechecked things. the white power wire, going into the ignition switch has 13v , when i turn on the headlight the white goes down to 11.4v.
so are u saying i have another problem? i have a big drain somewhere ?
do i need to recheck this while the bike is running, or is this enough info for now. I'll try to post the rest of the wiring diagram.

1st half

You still sound as though there is loss in your readings. This white wire comes from the Battery, through the main fuse to the Ignition switch, where it then returns to the fuse block to power the sub circuits. You can take a jumper and By-pass the Ignition switch so as to test to see if it is the culprit. I think OMR said to get a new switch and that is likely. But there is a good chance that there is also more voltage drop issues, 1 know area is the MAIN fuse in the fuse panel. How are the fuse clips and wiring at the fuse panel? Check with your meter for battery voltage on the in coming side and what it is leaving the fuse.

there is only 1 fuse. the white wire i have been testing at the switch goes directly to the fuse, then to the battery. i dont see any drop in V across the key switch terminal. it is only when the headlight is on that the V drops.

Only 1 fuse? Easy system, but then anything could blow it. I see why the guys are rewiring the old bikes.
OK so the current flow is being impaired along the wire path. Did you check the voltage just after the fuse, with the head light on, compared to the Batt side of the fuse?
This is a place in the wiring where voltage drop is common. If you have drop here then you will have it every where, including your Ignition coils. If you get rid of most of the voltage drop, then the headlight should be brighter, and you will get better spark.

when turning the headlight on i get a .3 V drop before the fuse and a 1.5 V drop after (UP front at the junction block.)

if u look at the wiring diagram above, follow the red wire from the tail lt to the junction block. this is where i have been doing my tests. just before and after the ignition switch. i took the block apart and put jumpers across the 4 pins.

1.5v at the junction, i.e. main fuse and clips. The fuse block shouls have a connector, you can bypass the fuse block and retest, suggest still using a in-line fuse and see if all of that drop is at the block. I have replaced that part of the factory wiring on my 82 1000LTD and my 80 550LTD. Both bikes start/ run/ brighter lights, etc.

ok i jumped around the fuse block(spade type,new last year).
i was loosing .2 v. cleaned spade block connections and 0 v drop now, with lts off.
with the lights on i get 12.7 v before fuse, 12.3 after fuse (still a loss)and 11.6 up front at junction block. so i have some tracing to due from the fuse to the front block.
these #'s change a bit with the bike not running and lts on.

by the way, i am running a new HID headlight that is rated at 35w.

That head light should be fine, also make sure that the ground wire to the chassis is good. Check both the resistance and voltage drop of the ground along the harness points. Mfolks says to use a "Detoxit" contact cleaner on the connections. This and others are good electrical cleaners.
I found on the way my 82 1000LTD was wired, that I could not loose the drop with out a MOD. Call it whatever, but I re-powered the fuse panel, these have 5 fuses. Taking the Highest draw circuit away from the Ignition switch contacts, this is the head light. I use a relay to handle the load of the circuit, still fused by my main 30AMP, then the Ignition brown wire and ground to pull the relay closed. I picked up voltage on both my Headlight circuit and my Switched Brown wire, coil etc.

Motor Head wrote:

That head light should be fine, also make sure that the ground wire to the chassis is good. Check both the resistance and voltage drop of the ground along the harness points. Mfolks says to use a "Detoxit" contact cleaner on the connections. This and others are good electrical cleaners.
I found on the way my 82 1000LTD was wired, that I could not loose the drop with out a MOD. Call it whatever, but I re-powered the fuse panel, these have 5 fuses. Taking the Highest draw circuit away from the Ignition switch contacts, this is the head light. I use a relay to handle the load of the circuit, still fused by my main 30AMP, then the Ignition brown wire and ground to pull the relay closed. I picked up voltage on both my Headlight circuit and my Switched Brown wire, coil etc.

i had o resistance at the tail lt, and batt, to ground .
how do i check a v drop through ground? just remove the ground and put my volt meter in line from the wire to ground?

Yes with it set to the same 20VDC scale as when checking the voltage, if it a digital, which it sounds like from your posts.
I know you've been checking and cleaning lots of connections, did you get a better voltage at the rear tail light Assy socket yet? How did the voltage drop at the junction block/ single fuse work out?
Oh and did you happen to measure the voltage at the positive side of your ignition coils?