I have a 2005 s-type R 4.2 s/c and the auxiliary water/sc pump has been unplugged, it looks like the pump has failed and melted part of the plug, I have got another pump and benched tested it to make sure it works and have also renewed the wiring from the relay and fitted new relay but till doesn't run, although if I jump the terminals on relay will run.


I think I'm right in thinking that the relay gets a signal from the RCCM (to ground) to switch relay so I have checked continuity from relay to harness in back of RCCM and all is good. Also took RCCM to BBA Reman (only up road from me) they gave it a visual check for any burnt out traces and said looked ok but couldn't fully check as they don't have settings for it.


my question is am I'm missing something more obvious and where does the RCCM get its info from to activate pump?

 

I believe there are 2 pumps so be sure which you mean: aux or SC (IC)? The SC (IC) may give a code but not always.

It sound like you do not mean the SC one.

I wonder if the workings are in the workshop manual? Free download....

 

I think its the auxiliary heater water pump has 2 pipe coming off it and has rubber mounting bracket, one hose is connected to the thermostat housing and runs behind back of header tank, from memory think the other pipe goes up on to the plenum chamber (will have to check later when home)