Topic: Oil Prerssure and Neutral Light Not Working

[Popwood]

My ‘75 750K sat all winter with a dead battery. Everything was fine when she went to sleep. Installed a new battery today after checking it was fully charged. Oddly, with key in first position, transmission in Neutral, the oil pressure and neutral lights on the “dash” don’t light. Bike will start normally, horn, lights, turn signals work as usual. While I was running the bike, I checked voltage at battery terminals and while revving engine didn’t increase to 13. 3 or so. voltage hung at about 12.6. I’m now making sure the battery has a full charge and reads about 13v. and will check again to see if voltage jumps when revving engine. In the meantime, any suggestions? Thanks for any help.

[Popwood]

OK, I checked again. Battery fully charged at about 13.15v. Ign switch on, bike in neutral, started easily. Checked battery voltage while revving to 4K, battery voltage read 12.6 or so and would not read higher with high revs. Clearly something disconnected or charging system died over winter? Where do I start looking?

[jaytee-nz]

I'd start by checking the wire connections in the headlight. The neutral and other lights connect in there. If the connections are good, you might need to take out the bulbs and check them (strange that both would fail at the same time). It may be that the bulb holders have corrosion in them preventing a good contact.

[bryanj]

If both dont work probably the black power feed wire to the dash lights

[Popwood]

Well, I will do that but given the battery isn’t being charged, I’m thinking the two dash lights not working have to do with
something wrong in the charging system.

[Don R]

 The lights should work fine with 12.6 volts, you didn't accidently reverse the battery polarity did you? There are identical looking batteries except the polarity (+and -) is opposite.

[Popwood]

Double checked just now. Battery connected properly. Thanks. I do recall a year maybe two ago bike died not far from home. I fixed the problem without much trouble, something simple, like a loose wire connection that prevented charging system from charging the battery. But I can’t remember exactly what I fixed. These memory thinks start to be a problem with aging; and I’m now 76. Another kind of wiring problem, I guess!

[bryanj]

Idiot light working has nothing to do with chrging unless battery totaly flat

[CycleRanger]

Check the bulbs?

[HondaMan]

It's not uncommon for these bikes to temporarily "lose" their Oil PSI light or Neutral light after a long winter sitting with old oil in them. The dirty metallic particles in the oil migrate to the metal contacts in those switches. Try fresh oil like Bel-Ray' EXL Mineral in 20w50 or at the very least, Castrol 20w50 Motorcycle Oil from your local auto parts store, and add a couple of ounces of ZDDP additive (like from here:
https://www.ebay.com/itm/290470073699?_skw=ZDDP+puls&itmmeta=01JPRJZ5X2CHWN9JPQ18VQF7J9&hash=item43a15d9563:g:rJAAAOSwR5dXRLo0&itmprp=enc%3AAQAKAAAA4FkggFvd1GGDu0w3yXCmi1d8YfXE4a7bWxIIgVx%2BTcU5SwdGxengBwf%2FAAK1f5QDfbDESIuh4XMKnV9bC%2FTGNL8GHNeSkHl83bYL3wDjmq6puQ3pn6Z9n4Mm1ejFE2DIAVgrdRSoB5tR8u3Y5f%2Fyjttq6Qq8m4Ymi3p41UeQVEX8uW%2BN81TncwpFd5etVNJ1IsEHT4ZbPSx%2FgmDyKLTGYcimOZJoAu955GJ6sjVT%2FhUTAM4fS8LY0JxYAaR3Fa0qA1J7bag%2Fkt%2BrQN5uJ3EShjPlaNpIVBCfaLr5uKAjqzHc%7Ctkp%3ABk9SR97f_JK2ZQ

and it will help dissolve those gritty contacts to restore better Oil and Neutral light functions again.

[scottly]

OK, I checked again. Battery fully charged at about 13.15v. Ign switch on, bike in neutral, started easily. Checked battery voltage while revving to 4K, battery voltage read 12.6 or so and would not read higher with high revs. Clearly something disconnected or charging system died over winter? Where do I start looking?

On a 750, the easiest test is to check the magnetism of the three screws that fasten the field coil inside of the alternator housing, with the key on and engine not running. If the screws are not magnetized, it points to a problem with the regulator and field coil part of the charging system. If they are magnetized it points to the stator and rectifier side of the system.   

[newday777]

OK, I checked again. Battery fully charged at about 13.15v. Ign switch on, bike in neutral, started easily. Checked battery voltage while revving to 4K, battery voltage read 12.6 or so and would not read higher with high revs. Clearly something disconnected or charging system died over winter? Where do I start looking?

On a 750, the easiest test is to check the magnetism of the three screws that fasten the field coil inside of the alternator housing, with the key on and engine not running. If the screws are not magnetized, it points to a problem with the regulator and field coil part of the charging system. If they are magnetized it points to the stator and rectifier side of the system.   

And don't forget to inspect and clean all the connectors in the charging system, from the barrel connectors under the sprocket cover to the Hitachi connectors for the regulator and rectifier. Dirt in the connectors causes bad flow of electricity problems.

[Oddjob]

I'd suspect the black feed to the dash lights, it feeds both the oil light and the neutral light. Bit of corrosion and they would both fail to work.

[Popwood]

UPDATE: I found an electrical multi-connector that was not connected. It was adjacent to the battery box and may have been disconnected when I slid the new battery in place. Now connected, the the oil pressure light and neutral light on dashboard working as normal. However, I also found that the charging voltage at the battery did not increase with the engine revving to about 4000rpm. I did Scottly’s test checking magnetism of bolts holding the field coil cover in place when just key on but bike not running. No magnetism, which indicates possible problem with regulator or regulator wiring.

I read more about how the regulator works and was surprised to learn the regulator changes voltage output based on battery condition. If I understand this, if the battery is fully charged, very little voltage is sent, if battery is less than fully charged, it sends more voltage until it is fully charged.

So here’s the big question: Since this is a new, fully charged battery, is it normal for the battery to read like 16.5 volts when engine is revving? Would I then expect that voltage to read more like 13.4 volts when revving if the battery was not fully charged?

[scottly]

The regulator limits the voltage to about 14-15v, so it should never get to 16.5v, regardless of the condition of the battery. If the battery is not fully charged, it may take some time for the voltage to rise to the point that the reg starts to limit the output of the charging system.
Check the voltage at the black reg terminal and the white reg terminal with the key on, engine not running. It should be 12v on both, assuming a stock regulator.

[Popwood]

OOOPs, serious typo. Should be “is it normal for battery to 12.5 volts” not 16.5 volts when engine is revving” Sorry

[BenelliSEI]

BEFORE doing anything else, don’t skip over HondaMan’s observation. Both these sending units can be “sticky” after a winter rest. They are easy to check. Both lamps permanently have power fed to them and the (-) ground comes from the switch.

With the ignition turned “ON” (bike not running) touch a small jumper wire from a clean ground, to the screw (securing the wire) on top of either switch. If the corresponding dash light comes on the switch is the problem. If not, there is a wiring issue.

[scottly]

BEFORE doing anything else, don’t skip over HondaMan’s observation. Both these sending units can be “sticky” after a winter rest. They are easy to check. Both lamps permanently have power fed to them and the (-) ground comes from the switch.

With the ignition turned “ON” (bike not running) touch a small jumper wire from a clean ground, to the screw (securing the wire) on top of either switch. If the corresponding dash light comes on the switch is the problem. If not, there is a wiring issue.

Popwood reported on reply #13 that the lights were fixed.

[BenelliSEI]

Oops. Good news.