I'm starting to rewire my cab on RLH62 and I have the LT wiring diagram for the 2nd batch of RLH's. I have a couple of questions:

Can anyone tell me how to read diagram to decode some of the terms on it, i.e. 14/ .012. Most of the wiring is the 14/.012 but I see some 35/.012 and 19/.044, plus a couple of others. I think it's to do with wire gauges and amperage but I'm not a electrician so I'm guessing, probably wrongly!

I take it where it says 'twin' and 'single' it means that there's a positive and negative wire that runs from the fuse or switch board to the fixture (twin) and single is where the return is done by the earth through the frame of the bus.

Thanks in advance for any help!

Regards,

Jim

My bus number (if any): RLH62

This refers to the no. of copper strands and the diameter of the strands.Your diagram will likely be in imperial measurements so that a cable 14/.012 describes 14 strands at .012 inches diameter of each strand.Nowadays they are all metric so you will need to find a metric equivalent cable when purchasing new cable eg 14/.05 means 14 strands at .05 mm diameter each strand, or more commonly.1.5mm/14 where 1.5mm is the overall outside diameter of the cable and 14 refers to the no. of strands. There should be no earth return through the frame of your bus.It should be insulated return.You will find that some returns will be common to several feeds depending on what they are, hence it will appear that some circuits only have one feed and others a feed and a return.You will need to study your diagram carefully to suss it out properly before you start. Hope this helps

My bus number (if any): RML2551

Thanks for that info. Now just to throw a further spanner in the gears, I'm in the States and we have that AWG (measured in gauge) rating for wires.

Using the info Steve gave me I found that 14/0.12 is the equivalent of 18gauge wire or 2mm wire rates at 8.5amps. Now if I just simply rewire with standard wire throughout, i.e. 12gauge (5mm/ rated for 27.5amps) will the increased wire size affect anything. I noticed that a lot of the original wiring had overheated and the plastic (or cotton covered in some cases) sheathing had melted or started to scorch. I have read in some wire supply websites that if you're unsure use a larger wire for safety.

Is it ok to do this or use the original (or modern equivalent).

Thanks again

My bus number (if any): RLH62

I just looked at the ratings again and I found a nearer size which would be 16gauge (3mm/10 amp). I think the 12 would not be the best!

My bus number (if any): RLH62

Your wiring will have got like that as the insulation breaks down with age.Using a higher rated wire is o/k so long as you protect it with the correct rating fuse.Remember that vehicle wiring must be flexible ie multistranded and the insulation must be of a grade resistant to flame/oils and water.So use a proper vehicle cable and not something you find lying around the house.

My bus number (if any): RML2551

Steve, thanks for the info. I intend to buy proper automotive wire in bulk (100foot spools), so I want to get the right stuff and not end up with a load of stuff that I can't use.

My bus number (if any): RLH62

you'll find "single" and "twin" refers to whether the cable is a single cable, i.e. a red or a black or whatever colour (sorry color in the USA), or a "twin" where the red and black are together as in domestic appliance wiring.

The easiest way to match it is take samples to your local cable dealer. Heavier cable won't matter as long as you don't uprate he fuses.

My bus number (if any): RML2532

Roy,

Thanks for the help. I thought that would be the case, so long as the fusing remained unchanged.

I spell colour correctly too as I'm a transplant to the US from Bolton!

My bus number (if any): RLH62

Two nations divided by a common language, and we talk about the north/south divide!!

My bus number (if any): RML2532