Relay problem

[tomjones2]

I fitted a relay to my z750 because i'm a muppet and cant switch the heated grips off after i have been using them, however the battery then started to die after being left for 2 days+.

A little poke around and the relay is warm after everything else is off, checked with voltmeter and there is nothing coming out of the end of the relay but I'm guessing the heat is probaly causing the battery to discharge.

Its a maplin job, can i have fitted it wrong, everything work as expected ignition on grips on igintion off grips off. Not that many option to screw up on a 4 point relay really.

Any ideas

On anther note anyone know a cheap relay that dosent kill your battery?

[timwilky]

OK, you have wired the relay into the switch live from the ignition?.

If so it will be permantly powering the coil and get warm whilst the ignition is on. How long after the bike was turned off did you feel the heat?.

Personally I would take a spur from the switched live through the on/off switch of the grips to the relay. In that way the relay is only activated when the ignition is on and the grips turned on.

Powering a relay with the engine running should not be sufficient to drain the battery.

[tomjones2]

OK, you have wired the relay into the switch live from the ignition?.

If so it will be permantly powering the coil and get warm whilst the ignition is on. How long after the bike was turned off did you feel the heat?.

Personally I would take a spur from the switched live through the on/off switch of the grips to the relay. In that way the relay is only activated when the ignition is on and the grips turned on.

Powering a relay with the engine running should not be sufficient to drain the battery.

sorry havnt made myself clear, the relay is connected the battery as normal and i think is activated by the rear light wire which is spliced with one of those blue things you can by from halfords. I certainly used a wire that is only live when the ignition is on.

batterh only goes down when the bike is not used, and therefore the battery is not charged

The grips work as they should its the relay that is staying warm all the time, bike hasnt been used for nearly a week.

[Philbo]

quick test. Unplug/disconnect one of the wires going to the coil of the relay, switch the grips on, and listen very carefully as you touch the connector back on and off the coil connection. Can you hear or feel the relay clicking? Do the same again with the ignition on. Can you hear/feel it now?

Do the same again with the grips switched off.

If it's wired correctly your relay should be clicking when the ignition is on, and the grips in either state.

If this is OK, then I suggest disconnecting your grips and give it a few days to see if the problem goes away. If it does go away with the grips disconnected and the relay is operating as described, double check the wiring through the relay to the grips.

How many wires going to the grips?
How have you connected them?
How are you using the relay?

[tomjones2]

Right found the answer to the relay problem, went to maplin and becasue its a 40a relay it when it was off it was creating a lot of resitance and therefore heat etc etc.

So where can I get hold of a cheap simple relay that when it is off it dosn't consume any power, I sort of want a switch that is switched on by an electric current, I though this was what a relay was. I dont know very much about electrics do all relay resist the current rather than being switched off?

[Philbo]

Dude, maplins bloke obviously doesn't have a clue, or your not telling us something!

The 40A rating is just the amount of electrical current the contatcs can take, and has absolutely hee haw to do with how the thing operates.

Did you try the tests I mentioned earlier?

OK...Relays 101.
A relay is just an elctro-magnet (coil), that makes a a set of electrical contacts make or brake depending whether the coil is powered or not.
If you apply, (in this case 12V), to the coil the relay will be "on", (assuming a normally open contact arrangement), this will close the contacts of the switch allowing power to flow to the heated grips in question.

Remove the power from the coil, the contacts return to the normally open position and power to the heated grips is removed.

Think of it as a switch, but instead on pressing a button, you are applying power to the coil.

Why not just use a normal switch? Yes you could, but if you want to power something that takes say 20amps, you would have to use a big ass ugly switch, not a pretty wee one that tucks away somewhere disctrete. And in this case your looking for an automatic operation.

If the operation of the relay and the grips is all good according the tests I mentioned, the only thing I can think of is that somehow you have a reduced voltage at the coil of your relay, say 5 volts, enough to generate a bit of heat over time, but not enough to change the behaviour of the relay.

With the bike all off, use a voltmeter to check for voltage accross the coil contacts, it should be zero.

Regarding the size of the relay, that depends on the grips. Do the grips have a "Wattage" or current reading on them? It might be something along the lines of "10A" or "24W". If they were 10Amp grips your relay has to have conctacts rated at 10Amps or more, preferably a bit more to extend its working life, and prevent the possiblity of welded contacts. And your coil voltage is 12Volts DC.

Good luck!

[Philbo]

Just had a thought, I'm assuming your relay has normally open contacts, and not normally closed? If they were normally closed, it would make sense of some of the what you've mentioned, as you would then have to have your relay energised to remove power to the grips...Therefore the relay coil has to be on , (creating heat and draining batteries over time), in order to switch off the grips...

How can you tell?
The relay will have the "N/O" on it for normaly open, and "N/C" for normally closed. Or it might show a diagram of the contatcs.

P.S. There is probably nothing wrong with the 40Amp relay you were using, as long as the coil valtage was rated for 12V DC and it has at least 1 set of normally open contacts.

How many pins/connectors did your relay have?

[Philbo]

On a side topic how do find the Z750..i'm thinking about swapping my Sprint for a new Z...

[tomjones2]

On a side topic how do find the Z750..i'm thinking about swapping my Sprint for a new Z...

I will do the relay tests, cheers for the replies,

The old Z is an awesome bike just mine has some suspension probs, the z is a little on the soft side generally but this can be sorted. I'm about 98kg with kit on so on the heavy side for stock suspension settings.

The good bits are an great engine, similar low down grunt to the sv and then 100ish hp at the top, very usable all day and keeps up with ss600. Gearbox is good nice light positive action and it dosn't vibe anything like as much as a twin which is really nice.

Riding postion is much more sat up the the svs and a lot more comfortable for town and not uncomfortalbe at speed. The bar are quite wide and make it easy to chuck into corners, more fun on the twisys bits.

Stock the old version has got almost no wind protection which means that crusing speeds are 85-90 something which i quite like, its to easy to sit at 120 on the sv. It does about 145 flat out, really was on the autobahn but things get very windy and viby not much fun really.

Basically i'm very happy with it and once the suspesion is sorted i cant see myself going for anything else for a while.

[Baph]

Dude, maplins bloke obviously doesn't have a clue, or your not telling us something!


I agree. I used to work in one, and if you're being told that a 40A automotive relay is the wrong one to use, you're being fed a crock of crap.

Please PM me the town that the store is in, I'm still friendly with some of the management in Maplin. They need a serious education if they're advising customers so poorly.

Yes, the relay will get hot, but that's more to do with the current the device (hot grips in this case) pulls throught the relay, combined with the current flowing through the coil. The relay itself can happily work with up to 40A. The bike will be putting nowhere near this amount of current out.

Anyway... If you can tell us exactly what is wired up to which pins on the relay, one of us should be able to tell you why the battery is going flat (if indeed the relay is causing it).

[tomjones2]

Hi cheers for all the relies. Sorry about the quality but you should be able to make out what is going on.

85 was connected to the live from the battery
30 was connected to the live for the grips and the cigarette lighter (now removed)
87 to the feed for the rear light cluster
86 back to the battery

Is this correct?

I have been dealing with the Banbury branch but the oxford branch originally advised me of the fitting order.

There was also a fuse between the battery and the relay and a fuse in the hot grips wire, does this have an effect.

Sorry for being stupid but am I correct in saying that the relay shouldn't get hot when the bike is not in use.

I might have misunderstood the guy in the shop but he didn’t explain think well, it took me three attempts to tell him that I didn't want the switch that he was trying to sell because I already had one and it didn't solve the problem.

Also I wired the negatives of both devices back to the battery, was this correct

[Philbo]

OK, nearly done.

Wire as follows-
85 Rear light cluster Positive supply
86 Negative feed anywhere - straight on to the battery terminal is ideal.
30 Positive supply through your fuse from the battery Positive terminal.
87 Supply out from the relay to your hot grips Positive supply connection.

No big deal if you mix up 30 and 87, as long as the other two are correct.

The fuses are always a good idea, and have no affect on the operation under normal circumstances.

This should get you going in jig time mate!

The way it was wired meant the relay coil was always energised, draining the battery over time. However the supply to the hot grips was coming from the rear lights! Thats why the grips stopped working when the bike was switched off!!! Have to say, I'm a little supprised you didn't blow a fuse with this arrangement...Should be OK though.

[tomjones2]

OK, nearly done.

Wire as follows-
85 Rear light cluster Positive supply
86 Negative feed anywhere - straight on to the battery terminal is ideal.
30 Positive supply through your fuse from the battery Positive terminal.
87 Supply out from the relay to your hot grips Positive supply connection.

No big deal if you mix up 30 and 87, as long as the other two are correct.

The fuses are always a good idea, and have no affect on the operation under normal circumstances.

This should get you going in jig time mate!

The way it was wired meant the relay coil was always energised, draining the battery over time. However the supply to the hot grips was coming from the rear lights! Thats why the grips stopped working when the bike was switched off!!! Have to say, I'm a little supprised you didn't blow a fuse with this arrangement...Should be OK though.


Cheers mate, i actually bought a new identical relay and fitted as per your instruction, works a treat only got heat in the right places when I want it. Will take maplins advice more carefully in the future. Have your self a virtual beer, many thanks.

[Baph]

Cheers mate, i actually bought a new identical relay and fitted as per your instruction, works a treat only got heat in the right places when I want it. Will take maplins advice more carefully in the future. Have your self a virtual beer, many thanks.
Glad to hear that it's sorted fella.

I've also passed your p*ss poor instructions (supplied by Maplin) on to the regional manager. It might interest you to know that their company policy is that they are not allowed to advise customers how to wire components of any kind, regardless of their background or knowledge. They are supposed to advise customers to call the technical helpline that's printed on the receipt (or used to be before they got the new laser printers).

Please remind the staff about this next time you're in the store, and thank them heartily for flattening your bike battery (though they'll claim immunity due to the above policy).

Mind, I never did agree with that policy, and disregarded it at every possible opportunity.

[tomjones2]

Glad to hear that it's sorted fella.

I've also passed your p*ss poor instructions (supplied by Maplin) on to the regional manager. It might interest you to know that their company policy is that they are not allowed to advise customers how to wire components of any kind, regardless of their background or knowledge. They are supposed to advise customers to call the technical helpline that's printed on the receipt (or used to be before they got the new laser printers).

Please remind the staff about this next time you're in the store, and thank them heartily for flattening your bike battery (though they'll claim immunity due to the above policy).

Mind, I never did agree with that policy, and disregarded it at every possible opportunity.


It seems a shame that shop people shouldnt give out instructions, but on the same note they need to know what there talking about. The guy and banbury did wind me up because he completly failed to understand what I wanted, and failed to recommend the right soultion and didn't seem to know how to wire the simple relay despite recomending another more complicated one. I did double check the instruction both on the phone and when i fitted them so i sure the mistake wasn't mine.

Many thanks again Baph,