Topic: My blinkers don't blink unless the RPM's are high??? Help

[Operator]

While trying to get the blinkers working on my wife's '76 CB400F, I realized that the blinkers work fine so long as the revs are up over 2000 rpms. If I let it drop back to idle, they become a solid light again. Rev it back up and they start blinking again.....I am elctrically challenged to start with so any input would be helpful.

Thanks!!

[flybox1]

bad battery, insufficient charging system and loss of power thru bad connections in your harness.
get a good, charged battery, and clean all your harness connections.

[Vinhead1957]

+1 flybox1

[TwoTired]

The stock system relies on a certain voltage level to blink.  In other words, the flash rate changes with the system voltage.  When you rev the engine, the alternator assumes the load from the battery and raises the system voltage during recharge.  I use the flash rate to tell me when the system voltage is low and the battery is discharging, kind of like an implied voltmeter.

Probably the first thing to check is what the voltage on the black wire to the blinker timer/relay is, compared to what is at the battery terminals.  They should simultaneously be within 0.5V of each other with all other lighting on.

My first guess is that many of the connectors, fuse clips and switches in the path between battery and blink relay have oxidized, which increases the line resistance and voltage loss.

There are a lot of people that simply replace the stock relay with an electronic one which is not voltage sensitive and ignore the other voltage loss issues until something else goes wrong, with charge issues likely.

Another common issue is that some or all of the signal lamps have been changed from 1034 to 1157  and 1073 to 1156.  These fit into the same sockets but have a different wattage, which changes the stock flasher cyclic rate.

Then there is the issue of proper and good integrity ground paths...

[grcamna2]

The stock system relies on a certain voltage level to blink.  In other words, the flash rate changes with the system voltage.  When you rev the engine, the alternator assumes the load from the battery and raises the system voltage during recharge.  I use the flash rate to tell me when the system voltage is low and the battery is discharging, kind of like an implied voltmeter.

Probably the first thing to check is what the voltage on the black wire to the blinker timer/relay is, compared to what is at the battery terminals.  They should simultaneously be within 0.5V of each other with all other lighting on.

My first guess is that many of the connectors, fuse clips and switches in the path between battery and blink relay have oxidized, which increases the line resistance and voltage loss.

There are a lot of people that simply replace the stock relay with an electronic one which is not voltage sensitive and ignore the other voltage loss issues until something else goes wrong, with charge issues likely.

Another common issue is that some or all of the signal lamps have been changed from 1034 to 1157  and 1073 to 1156.  These fit into the same sockets but have a different wattage, which changes the stock flasher cyclic rate.

Then there is the issue of proper and good integrity ground paths...

+1 on what Flybox and Two Tired say.

[Operator]

Thanks Gents.....off to the garage

[Duanob]

Put the battery on a charger and see if that fixes it. If it does then you will possibly be chasing reaons why the battery is losing it's charge.

[welard]

I had exactly the same thing happening recently (except I have a 76 CB750F)...whilst revving the bike no problem with blinkers as soon as I would let throttle off...they stopped.

I replaced the flasher relay (digital relay about $10 on ebay) and they blink nicely now at any revs. Even replaced globes with LEDs and the relay fixed the fast blink rate normally associated with LEDs.

I'd try that first before shelling out for a battery.

[flybox1]

I had exactly the same thing happening recently (except I have a 76 CB750F)...whilst revving the bike no problem with blinkers as soon as I would let throttle off...they stopped.

I replaced the flasher relay (digital relay about $10 on ebay) and they blink nicely now at any revs.

...probably because the new electronic flasher relays can flash with less load. 
this still does not fix the underlying issue of one or more of the following....poor charging system/bad battery/corroded harness

yes, a new battery is not required, but a properly working and charged one is.

[Bob Wessner]

If they have never been cleaned, one of the best investments in time you can make (and it's cheap, maybe a cold beer.. or two  ) is to set aside some time to go through the entire electrical system, one connection at a time, and clean them followed by applying some dielectric grease before putting them back together.

[ofreen]

Bob's advice about cleaning  connections is excellent. Good connections pay dividends throughout the bike. But I've had my '75 750 since it was two years old and even back then the flasher was less than energetic at idle. By all means, check your battery, charging system and clean connections. But the electronic flasher is still a worthwhile upgrade.

[Menno]

My guess... check if the amps on the lamps are correct. I can't remeber what it should be but if you have a 12 volt 15 amps in stead of a 12 volt 5 amps lightbulb... well there you go.

[Bodi]

The symptom you describe is most typical of an undercharging battery because the electrical system is either degraded (usually harness connectors) or overloaded. It could just be a bad battery: because of its small alternator, the 400F will always be discharging the battery at low RPM and a weak battery will let the system voltage drop a lot then although OK at riding RPM. With the engine running above 3000 RPM on a fully charged battery the battery voltage should get to 14V or thereabouts.
Confirm the voltage is OK first, the battery should stay above 12V at idle for quite a while if in good shape and fully charged. The system voltage - you can measure that between any black wire and ground (any shiny bolt into the frame) - should be within about one volt of the battery reading. If that's OK then possibly the flasher is bad, or you have non-stock lamps in the flasher. While you're there, measure voltage from a green wire to battery "-" with the key on but not running: a voltage above 1/2 VDC suggests a grounding problem: the battery to frame ground cable or the harness to frame connections are not right.
The signal flasher works on heat: a small heater is connected in series with the signal lamp load. Lamp current through that heater warms a thermostatic switch that opens when hot: that cuts off the lamps - and the heat - so it cools down and turns on the lamps again. Reduced system voltage means less heat, reduced lamp wattage means less heat. If it doesn't get hot enough it never cuts off the lamps.
As suggested, cleaning the connectors throughout the harness can do wonders solving electrical problems. On the 400 make sure you check the ones under the left side engine cover, these are in the alternator circuit and any corrosion or damage will cripple the alternator output leading to just what you describe.
The other good suggestion is to look at your headlight. It was very common to replace the original feeble sealed beam with an H4 halogen headlight: using a 55/60W lamp (the standard H4 automobile lamp) is going to cause charging problems. If you have one of those, find a 35/35W lamp (common on scooters) and install it. It will be dimmer than the 55/60 but much better than the factory lamp and definitely enough for night rides.

[PeWe]

I went into this problem on a holiday in Italy almost 30 years ago. I suddenly lost headlight under 4000 rpm. Blinkers were all glowing constantly. I had to drive keep engine over 4000 rpm to see the road...

It was battery that was bad. Had to be replaced. Battery with a bad cell will not be charged like that.

[Operator]

A thorough cleaning is in progress..battery doesn't seem to be the issue...will be checking bulbs this afternoon and following up on the replacement digital relay switch at the local NAPA parts shop.

Thanks again for all the input

While we are all talking about electrics.....how do you test the horn unit (original part) to see if it is functional... I want to test it before I consider re-installing it on my project. I know I know I'm electrically challenged..

[flybox1]

how do you know your battery is not the issue?
what test did you perform to confirm this? 
...remember, you are electrically challenged. 


your horn operation is simple.  there are 2 contacts.
one contact goes to ground, the other is powered (12v)

[Operator]

I don't...I just guessed ....wonderful part about being challenged...you can guess and still be right!!

Put it on my charger overnight...checked in the morning..the charger has a function where it tests and shows you a percentage reading on the battery quality..sitting at 95%.

For comparison I put my 750 battery on it and it shows at 75% and all works very well..

On with the hunt....thanks for the horn advice

[flybox1]

I don't...I just guessed ....wonderful part about being challenged...you can guess and still be right!!

Put it on my charger overnight...checked in the morning..the charger has a function where it tests and shows you a percentage reading on the battery quality..sitting at 95%.

95% of crap is still crap 

you need to get a volt meter, and check the voltage across the leads a few hours after you take it off the charger.
what is this voltage?
then, attach it to your bike, and turn on the headlight. 
what is this voltage? 
start your bike, let it idle.  what is the voltage?
increase rpms to 2000.  what is the voltage?
3000rpm voltage?
4000rpm voltage?
this will show us battery charge and how well your charging system is working.

most of this electrical stuff, and how to diagnose your electrical system is in  FAQ section, as well as in your shop manual.

[calj737]

I don't...I just guessed ....wonderful part about being challenged...you can guess and still be right!!

No assumption based upon presumption can ever be trusted. Do as Flybox says and guarantee your findings. Here's a step-by-step procedure to ascertain the actual condition of your entire electrical system. (You'll quickly discover that those who offer help, stop doing so when the owner with a problem stops taking good advice or takes shortcuts.)

http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf

[Operator]

I don't...I just guessed ....wonderful part about being challenged...you can guess and still be right!!

This was my shallow attempt at humour...I am certainly not snubbing the provided advice...and the last thing I want to do is take shortcuts. ...one of the reasons I posted the charger diagnostics result was to ascertain if the battery could be removed as part of the issue based on the 95% reading...clearly not. That said i will be going through all possible issues based on the advice provided. I will be cleaning for the next few days until I can purchase a multimeter....at that point I will carry out the test as advised.

Looking to learn as much as I can along the way.....al advice is being taken to heart and I will update as I go along.

Thanks again gents.

[TwoTired]

Put it on my charger overnight...checked in the morning..the charger has a function where it tests and shows you a percentage reading on the battery quality..sitting at 95%.

All it is telling you is that IF the battery is good, it SHOULD have a 95% charge.  Yes, the charger is making the assumption that the operator connected a known good battery. 

Your assumption is that an artificial intelligence is more knowledgeable about a situation in which it is placed than you are.  I wonder, does your charger have optical recognition?   

Should we ask if you read the charger's operator manual or its specifications/limitations?

[Nic]

I recently replaced my battery, I have one of those wall wart conditioner things, it reckoned the battery was charged up and went to green led but the battery was kaput.

[Operator]

All it is telling you is that IF the battery is good, it SHOULD have a 95% charge.  Yes, the charger is making the assumption that the operator connected a known good battery. 

Your assumption is that an artificial intelligence is more knowledgeable about a situation in which it is placed than you are.  I wonder, does your charger have optical recognition?   

Should we ask if you read the charger's operator manual or its specifications/limitations?

Point taken....thank you