Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: fourfive on November 02, 2023, 09:50:07 PM
-
The two red wires going to the fuse box on my 1975 cb550 F1 usa are getting warm while the ignition is turned on. Is this normal? If not has anyone any ideas as to what may be cause?
Thanks Ian
-
50 year old wiring breaking down could be a cause of hot wires. Has your bike got electronic ignition fitted or points?
-
bike has still got points
-
Slightly warm is not a huge problem. Warm to hot is. Check the spade connectors in the block and the fuse holders for corrosion.
-
The two red wires going to the fuse box on my 1975 cb550 F1 usa are getting warm while the ignition is turned on. Is this normal? If not has anyone any ideas as to what may be cause?
Thanks Ian
When you say getting warm while the ignition is turned on do you mean without the engine running? In this case heat generation is normal as long as it's not crazy hot.
In the 1960s on Minis doing this was generally to be avoided as depending on the position of the points coils could get very hot indeed together with the wiring. I once accidentally left the ignition on overnight whilst working on the car, luckily the battery was not in great condition - I was lucky not to have burnt out the coil.
As has been said cleaning up connections will help reduce the issue. There does come a point where old wiring can become badly oxidised within the insulation such as in rear lighting looms that can be replaced quite easily. Other areas of concern are where wiring is moved around such as headstock area or subject to lots of heat such as close to a hot engine.
I replaced my loom on the 400 to avoid future problems but it was probably not necessary. On my 500 I have retained the old loom as it appeared to be good visually - it just needed the outer tape binding replacing. On the 500 K1 my loom is not particularly expensive so I might regret not replacing it if I encounter problems.
-
The old pvc insulation is good for 70degc. You won’t be able to touch it for long!
But of course that doesn’t mean you don’t have a problem. Is the temp pretty similar along the full length of the cable. If it is, it’s probably ‘normal’. If the temp is much higher at a terminal, you may have a high resistance joint, which needs dealing with as eventually it will burn out. I expect folk will wonder why the fuse doesn’t blow. The reason is due to localised heating I2R. The current remains below the fuse blowing threshold, but the the resistance has risen generating more heat. It’s the primary cause of most connection failures and domestic house fires.
-
Thanks for all the above advice, I've cleaned the joints up and the fuse holder and now with the ignition on but engine not running there is very little if any warming of the two red wires.
The reason I had the ignition on in the first place is I am trying to get the headlamp to work. I have no power to the headlamp fuse and looking at the wiring diagram the black/yellow wire goes to the dip/beam switch. The black/red wire goes to the right hand switch. Where does that circuit get it's power from? If I put a live to the black/yellow wire going up to the switch dip and beam work.
-
There is one wire in the headlamp shell that DOES NOT connect to the same colour, i vaugely remember the femal connector having a yellow stripe on the female plastic sleeve.
Enlarge your wiring diagram and follow the wires.
Power goes into rh switch on a black then comes out on 2 different colours depending on position, 1 for park/side lights and one for head, both go down to fuse box, head then comes back up to headlamp and to lh switch.
Hope that helps