Any electrical boffins here?

MarkShelley

MarkShelley

Very similar to Paolo Maldini
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I have a problem with my XTZ750. It fried the regulator/rectifier last week. I have replaced it and have been on a couple of short runs without incident but the fact that the lights do not get brighter when the bike is revved led me to believe all may not be well.
I have a multimeter and looked up a method of testing the charging on the internet. I tested the DC Voltage across the battery terminal with the bike revving at 2500rpm and the measurement was 16.3
As this was higher than 14.8, the fault finding instructions told me to put the black lead on the neg terminal of the battery and the other onto the red (output) lead from the RR whilst the bike is ticking over. The reading should be around 0.2 apparently. Mine was 13.5!
The instructions told me that the fault must be on the red lead from the regulator to the battery +ve terminal. I have checked it and there does not appear to be a problem with it.
Any suggestions before I drop it off to somebody who knows about electrics!
 
borrow or buy a decent multimeter I had a problem like this with a triumph tiger 955 It was my dopey meter was goosed on the 20v DC scale it said 16 when in fact it was just about 14

what happens if you go out to your car lift the bonnet and measure the voltage thats usually a good guide if it's been sitting you're looking at 12.5 to 13.2 volts ish
 
Jaythro said:
borrow or buy a decent multimeter I had a problem like this with a triumph tiger 955 It was my dopey meter was goosed on the 20v DC scale it said 16 when in fact it was just about 14

what happens if you go out to your car lift the bonnet and measure the voltage thats usually a good guide if it's been sitting you're looking at 12.5 to 13.2 volts ish
Click to expand...

Just tested on the wifes Ka.......12.58V, so the meter is OK.
 
Guessing that the 0.2V referred to in your first post should in fact be with the +ve lead (red) of the meter on the R/R output and the -ve lead (black) of the meter on the positive terminal of the battery.
 
nick.ct said:
Guessing that the 0.2V referred to in your first post should in fact be with the +ve lead (red) of the meter on the R/R output and the -ve lead (black) of the meter on the positive terminal of the battery.
Click to expand...

D`you know what. You are correct! Just checked the instructions. I will give that try in the morning and see what happens!
 
MarkShelley said:
D`you know what. You are correct! Just checked the instructions. I will give that try in the morning and see what happens!
Click to expand...

The 0.2V referrred to will likely change with the amount of current flowing from the R/R to the battery and is determined by the resistance in the wire and connectors between the R/R and battery.

The amount of current going down the wire from the R/R to the battery will depend on the load (lights on etc), the state of charge of the battery (fully charged battery will take less current from the R/R than a nearly flat one) and the revs of the engine (more output from the R/R at revs greater than tickover)
 
The reading with lights off fluctuated between 0.3 and 0.4 so I guess there is probably nothing seriously wrong on that circuit.
 
MarkShelley said:
The reading with lights off fluctuated between 0.3 and 0.4 so I guess there is probably nothing seriously wrong on that circuit.
Click to expand...

That looks to be about rightish and probably not the problem (it'd be nice to see it lower tho)

If you are able to measure the other half of the circuit, ie the voltage between the negative terminal of the battery itself and where the R/R connects to the frame of the bike. It should be the same or less than the 0.3- 0.4V that you've measured already. If this is higher, start to look at the lead that connects the negative terminal of the battery to the frame / engine block. Corrosion here can cause the problems you've described
 
nick.ct said:
That looks to be about rightish and probably not the problem (it'd be nice to see it lower tho)

If you are able to measure the other half of the circuit, ie the voltage between the negative terminal of the battery itself and where the R/R connects to the frame of the bike. It should be the same or less than the 0.3- 0.4V that you've measured already. If this is higher, start to look at the lead that connects the negative terminal of the battery to the frame / engine block. Corrosion here can cause the problems you've described
Click to expand...

That was also the next thing on the list I have. It actually said one lead to the -ve battery terminal and the other to the black cable leading from the RR, but if the RR does not have a black cable you should put the lead onto the housing of the RR. I got a reading of almost 13V:eek:
 
MarkShelley said:
This is the fault finding chart. It suggests adding a new wire to run directly from the RR to the negative terminal of the battery. Is this a good solution?

http://www.offwidth.co.uk/bike/general/electrical_fault_finding.pdf
Click to expand...

I'm not familiar with your bike or indeed the colours of wires on it. Having said that, the will be an electrical connection from the R/R to the frame of the bike / negative terminal of the battery, either a wire or by the fixing of the R/R to the frame. Measuring the voltage between this point and the negative terminal of the battery should be fractions of a volt. Anything greater than this would indicate a fault in this part of the circuit.
Adding an additional wire to bypass this fault, as a solution is not as good as, IMHO, fixing the original fault (likely only to be a loose/poor connection caused by corrosion)
 
There is a black lead which bolts to one of the RR fixing bolts but it comes out of the loom with the wires which go into the RR. It is not obviously linked to the RR in any way. I did take the reading to this as well and got the same reading.
I know what you mean about finding the fault, but is there any potential downside to simply adding a wire straight back to the -ve battery terminal or will it just do the same thing as fixing the bad connection?
 
For me, I'd like to do a few more checks (cable resistance and voltage) before adding extra wires, not least checking the connections between the battery negative terninal and the frame of the bike.
You are suggesting connecting a wire between two points that you have measured 13 volts across............. not always a good idea unless you are really sure why those 13 volts are there.
If you go down the route of putting in the extra wire, may I suggest you put a fuse (maybe 10 Amp) in line with the cable so that if end up shorting out the battery or whatever the fuse will blow and you will be wise that this was not the fault and you can investigate further
 
Cheers Nick. Good advice. I will try and give it a go before I disappear down to Kent for most of the next few weeks. When I do get it sorted I will post the problem.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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