Another Dim Headlight Post

[Vickersguy]

After reading the dim headlight posts, because it's rude to make a post on questions already answered, my headlight issue on my '83 is similar, but different. It's also weird. The classic trouble shooting path is to check the Hi/Lo switch, which I've done. The switch is good, but I'm not getting battery voltage at the switch. I have 12.8 volts at the battery but only 10.07 volts at the blue wire supplying power to the switch.

At the H-4 plug to the bulb, I have 11.7 volts to the low beam, ( the same voltage if I use a frame ground or the neg. batt. post, so no ground issue...) and 4 volts to the high beam. I figure 4 volts is the "trace" voltage the RLU uses to check the condition of the filament of the high beam. When I switch to high beam, I have 11.7 volts to both hi and lo plug sockets. I think this means the RLU is working properly. If the headlight is plugged into it's socket, I get the panel headlight white lamp lit on Lo and it goes out on Hi. If the headlight is not plugged in, the white panel lamp is lit all the time. I'm beginning to think the next step is doing the solder joints in the dash panel. However, one guy with an issue exactly the same as mine, did the solder job and it made no difference. It ended up he had a bad bulb and I do not. The H-4 bulb is totally good.

I have a 2 volt loss between the battery and the headlight switch and that power goes through the dash panel. It also seems clear that the dim switch only controls where the CMU sends the power, to the Hi or the Lo on the headlight. So it's the CMU, right ? and the solder joints... I'm going to pull and return all the relays behind the headlight just to be sure there are good contacts there. Just not sure where to go from here... OH, forgot to mention, my self canceling unit does not work. I don't think that affects the headlight though.

[Flyinfool]

In order to get meaningful voltage readings the RLU must be plugged in and a good headlight bulb must be plugged in. Otherwise the RLU is trying to fix the problem for you and giving bad info.

 

The HI/LO switch has 3 wires to it. Yellow, Green and a Blue/Black. The blue/black wire is the one that is supplying power to the switch. It should show pretty close (within .5V) to battery voltage at all times that the key is on. If not start following it down where it goes thru several connectors until you find the bad connection. once you have proper power to the HI/LO switch then we can start chasing the other problems.

NOTE - In some places wires will change colors as they go thru connectors, so watch for that so as to not get confused and end up chasing the wrong wire.

[Marcarl]

If you are still running the OEM fuse block, better change that first.

[Vickersguy]

Well, the data is in and it's inconclusive. I spent several hours tracing the path through the XVZ12TDK diagram which seems to have the correct wire colors that exactly match the wires on my bike. The easy part is from the battery, thru the main switch, back to the fuse box, then to the start switch, then the reserve light unit. All that was easy. I am loosing 1.4 volts through that run. The worst offender is the kill switch but the key switch is not far behind. I will clean the kill switch anyway. There is a forum post on that, which I downloaded. It gets complicated at the RLU. The dim switch is not directly connected to the headlight. One output from the RLU goes to the dim switch, then goes to the computer on the hi/lo wires. Another output output from the RLU also goes to both the computer AND the H-4 bulb. I suspect the original design uses diodes for switches in this system. RLU's go for short $ on e-bay. I am opposed to just buying stuff helter-skelter to fix problems but I have no clear direction to go from here. On low beam, I've got 4.8 volts to the lo beam and nothing to the hi beam. On hi beam, I have full voltage to both hi and lo beams. This makes no sense to me at all. On lo beam, the white headlamp light on the dash is illuminated. When I switch to hi beam, the blue hi beam indicator goes on and the white headlamp indicator goes out. The fix seems to be this :

#1 ) clean the kill switch contacts to reduce the resistance in the circuit. #2 ) get a used RLU from e-bay, and #3 ) plan on soldering the computer following the forum post instructions ( I'll have to locate those again ). The early Mk1 board is somewhat different from the later Mk2 board, I understand. Never the less, I've discovered no clue that would tell me it's the computer board or that it's the RLU. If there is a test I could do that would solve this I'm all ears.

[Patch]

OH, forgot to mention, my self canceling unit does not work. I don't think that affects the headlight though.

 

here's how to check this circuit 7-28

 

https://www.venturerider.org/wiring/83%20Yamaha%20Venture%20electrical%20info.pdf

[Patch]

In order to get meaningful voltage readings the RLU must be plugged in and a good headlight bulb must be plugged in. Otherwise the RLU is trying to fix the problem for you and giving bad info.

 

The HI/LO switch has 3 wires to it. Yellow, Green and a Blue/Black. The blue/black wire is the one that is supplying power to the switch. It should show pretty close (within .5V) to battery voltage at all times that the key is on. What is the volt reading?

If not start following it down where it goes thru several connectors until you find the bad connection Step 2 searching for voltage loss.

once you have proper power to the HI/LO switch then we can start chasing the other problems.

NOTE - In some places wires will change colors as they go thru connectors, so watch for that so as to not get confused and end up chasing the wrong wire.

 

[quote=Vickersguy;1054142

I am loosing 1.4 volts through that run From where to where? Separate each connector then measure - reconnect - measure further along that harness, note down any additional losses.

The worst offender is the kill switch but the key switch is not far behind. ​Separate circuit & issue

I will clean the kill switch anyway. There is a forum post on that, which I downloaded. It gets complicated at the RLU.

 

The dim switch is not directly connected to the headlight. One output from the RLU goes to the dim switch, then goes to the computer on the hi/lo wires.

If there is a test I could do that would solve this I'm all ears.

 

Just take it one step at a time and, one circuit at a time, answering Jeff's post clearly.

I'm attaching a diagram the thicker circles are where you need to report voltage reading and please state the color of wire you read and voltage. The thinner red mark is after the bulb.

Measure from switch, at each end of connector high and low beam wires

Voltage loss can be from: switch contacts, connectors and the wire itself

[Vickersguy]

I'm still cleaning connectors and switches. It does get boring and gives me time to think. Thoughts like, " What if I skipped cleaning all this stuff and just jumpered a hot wire from the battery directly to the blue/black wire on the dimmer switch ?" I got two answers that shed some light on the situation when I did this. #1 . The white headlight dash lamp went out. That let me know that I'm not wasting my time cleaning connectors and switches. The headlight dash lamp going out let me know that the delta V. between battery voltage and whatever voltage is getting to the RLU and the "computer" is important to how the system works. The #2 observation was that the headlight low beam went out completely. No more dim orange 4.8 volt glow. When switched to high beam, it was very bright. I didn't check to see if there was power to both high and low beam elements at the same time, but disconnecting the jumper wire did change the output light level. It got less bright. I do know that when the High beam is on, without the jumper connected, there is power to both low and high beam at the headlight plug. Also the headlamp symbol on the LCD never went off. I don't know what that all means, but I'm glad I tried the experiment. Overall it's still annoying. It reminds me of the thermos bottle joke. It keeps hot stuff hot and cold stuff cold, but how does it know? Whatever... I'm back to cleaning connectors and switches.....I'll get some voltage readings when I'm done.

[Patch]

You are not wasting time by opening, cleaning and checking contacts, weather they be connector or switch;)

 

You can plan a new circuit to the lighting but, you should consider how to tie in the existing switches and monitor.

 

I would use a relay if I were to do so.

 

You mentioned earlier that the lamp is fed after.... in such a case you just keep probing till you get to the end of the circuit.

 

If you have questions keep asking for answers, we enjoy watching others labor;) but, it is best to directly answer each question or the club may think we're overloading you.

 

Flyinfool: asked "The blue/black wire is the one that is supplying power to the switch. It should show pretty close (within .5V) to battery voltage at all times that the key is on."?

Marcarl: asked about the fuse box?

 

By diving the harness at each connector and measuring drop you will eventually find the cause. Contacts you can restore and, if it proves to be wiring then you replace/jumper just the length required.

 

Its not an unrewarding experience and truly expands your independence should chit happen out there somewhere.

[Vickersguy]

It's the reserve lighting unit that is bad. Here's the reasons I made that call.

#1 ) The headlight indicator in the dash was lit. That is independent of all the other circuits being looked at. It's voltage source comes from the RLU and returns to the RLU. I know I have good grounds and I know my H-4 bulb is good, yet the light is on. That's a point against the RLU

#2 ) When I jumper out the whole shebang, I get proper operation of the system, but the low beam will not work. Everything works fine except I have no low beam power. Again, another point against the RLU.

#3 ) I put the battery charger on to make up for any low voltage conditions that might compromise the operation of the system. That bumped up the system voltage well above any failure mode that might have been caused by a low voltage condition. There was no improvement in system function.

#4 ) A tested used RLU was available on e-bay for $5.60, including shipping.

#5 ) My cheap chinese soldering pencil for soldering up the "computer" is burned up and no good and bad and don't work and awful.

 

#6 ) Diodes are frequently used as switches in inexpensive logic circuits. They are reliable and can handle a fair amount of current. A bad diode, in a diode switch logic circuit, would give the kind of symptoms I'm looking at. Those symptoms would be low voltage on both hi and lo beams, ( current flowing through a resistance in reverse through a bad diode ) Also an open diode would cause the headlamp light to go on and I would have no power to the lo beam. These are typical failure modes of diode logic circuits.

The scary thing is that they are very reliable. What will take out a diode is an over voltage condition, possibly caused by a bad voltage regulator, possibly damaged by too high a load on the system, which would have symptoms like the burned up alternator plug I just removed...... I think I need to stop thinking about this for a day or so. I'm gonna loose my Zen.

[Vickersguy]

Just a thought, as the replacement RLU wanders slowly across the country. Now that I've got it out and on the bench, I think I'm going to take some resistance/continuity readings off this RLU, then the same readings off the next one, when it finally shows up and compare the results. It might be that I could shed some light on the RLU mysteries or at least give some readings someone else might use in future. That good/bad comparison could prove helpful to someone. Or not. It remains to be seen.

[Venturous Randy]

The vast majority of headlight problems on a 1st gen is the CMU or CMS due to two reasons. The first is cold solder joints and cracking around the solder joints. I suspect that a big contributor on this is when the wire bundle is hooked into the back of the CMS that it is somewhat heavy and it pulls down on the pin connections. You will find that when you disassemble the CMS and look at the solder joints that it will be one of the ones that go thru the board and has a pin that goes into the connector. You will usually see where there has been some arcing at the solder joint that is bad. Kind of the chicken or egg thing, did the solder fail or did the pulling down on the connector cause the joint to crack.

Anytime I have fixed a CMS with the solder joint problem or even had the dash out, I have always used a good plastic tie to hook around the bar above the connector to pull up on the bundle of wires, taking the weight off the connection. In fact this is a good thing to do as preventative maintenance.

Randy

[Vickersguy]

I figured it might be a good idea to check those solder joints while I wait for the new RLU to show up in the mail. I mean, how hard can it be, couple nuts, a plug or two, badda bing. There you are... Well, it didn't go like it does in the movies. One of the nuts on the instrument housing mounting posts wouldn't break free. The nuts were really tight. So I put some stress on it and heard that crunch sound where the stud broke free of the housing and started spinning freely, the nut still tight on the stud. So I reach in with some slip joint pliers and put some stress on the embossment the stud is anchored in. It keeps spinning, so I grab tighter. The plastic around the stud starts breaking up and the stud is still spinning. Finally enough plastic broke away that I could grab the stud with the pliers and the nut finally broke loose. What a mess. I mean, I can fix it back up with epoxy and fiberglass but it's such a pain when things go that way. I have 8 or 9 cold solder joints. They are bad enough I can see them with a magnifying glass. Now I get to wait for the new soldering pencil to show up in the mail too. On the bright side, except for those bad solder joints, everything is remarkably good condition. All the connections and plugs are shiny and oxidation free. So it goes....

[Vickersguy]

Okee Dokee, Here we are. The problems are fixed. The new solder station showed up and the cold solder joints are redone. I'm not one who will hide bad choices. I was wrong on all counts about the RLU. My readings were same/same on my two RLUs. Because they are both good. I say "problems" because several things changed after I re-installed the CMS after the re-solder job. I now have a level reading on the gas gauge which I didn't have before and all the warning LCD's have gone out but the oil pressure, which should be on when the bike is not running and the battery, which should also be on when the stator isn't charging. Good stuff. So the dim headlight issue, if you have it, is, in all probability, bad solder joints inside the CMS. Off to the next issue.

[Patch]

Okee Dokee, Here we are. The problems are fixed. The new solder station showed up and the cold solder joints are redone. I'm not one who will hide bad choices. I was wrong on all counts about the RLU. My readings were same/same on my two RLUs. Because they are both good. I say "problems" because several things changed after I re-installed the CMS after the re-solder job. I now have a level reading on the gas gauge which I didn't have before and all the warning LCD's have gone out but the oil pressure, which should be on when the bike is not running and the battery, which should also be on when the stator isn't charging. Good stuff. So the dim headlight issue, if you have it, is, in all probability, bad solder joints inside the CMS. Off to the next issue.

 

 

Yes I don't recall reading those issues in the original post... So for sure the guys would have pressed that as likely.

Well you sorted it and that a win

[Flyinfool]

The 1st gen does not have an oil pressure switch. It does have an oil level switch which should be off if there is oil in the bike. So that one is not an issue either. This light can occasionally lite up under hard acceleration as all of the oil sloshes to the rear of the engine and the float that is near the front will show a low oil level. the oil pickup is toward the rear so this does NOT indicate a problem.

 

There is no charge indicator light either, there is a battery electrolyte level light. Many 1st gens have that bypassed because many new batteries do not have the extra hole to put the sensor in.

 

Now all your problems are gone.........

[Venturous Randy]

Just out of curiosity, did you plastic wire tie the wire bundle to a bar above it to take the weight off the connector and the board?

Randy

[Vickersguy]

Yes I did but I didn't take a pic. It took a moment to figure out how to tie it off because the ties must be attached to the inst. pod and not other stuff. Used a glue on wire tie base to anchor the tie.