Both my RMs have one of these
behind the offside bench seat back.
I’ve recently had problems
with poor cranking speed when starting. This is despite having fully charged new
batteries and new 50mm² copper cables from the switch to the batteries and
between the batteries. Then I noticed that one of the battery isolating switch
terminals was warm after starting. I mentioned this to at my local heritage
railway as they use the same switch CAV on several of their diesel shunters.
The switch develops a high resistance when the internal contacts are corroded
or worn and this is apparently quite a common problem. My switch was showing a
resistance of 80 ohms on the positive pole – far too high.
I removed the switch and the
railway repaired and refurbished it for me. The resistance is miniscule now.
Starting performance is now
brilliant. So, if starting is a problem, check your battery isolating switch as
well as everything else.