Charge cooler water pump fuse/relay Options

[rhodesyboy]

Hi basically I am struggling with my water pump for the charge cooler and I'm just doing voltage checks to see whats what.

Basically what I have found is that at the relay there is no voltage from the ECU for the magnet side of the relay, even when I give it a good rev there is no voltage across the two slots with the relay taken out.

Then for the slot that should supply the voltage to the pump is only getting 7 volts, so I then went to the CDS fuse and unplugged it to try and get a voltage but when I unplugged it there was no voltage at the pins and obviously none at the relay but then when I plugged it back in it all came back.
I did check there is continuity across the fuse, is there any point checking for resistance in this fuse? If so how much?

So has anybody got an idea or experienced this kind of problem?

Also I am checking it right aren't I, taking the fuse or relay out and probing where it should plug in and checking the potential difference (voltage) across?

[Bitter]

Usually power is from a fused source to the coil and the computer grounds the coil to close the contacts.

[rhodesyboy]

Ahhh ok so I'm probably looking at a blown fuse on the coil side too? Any idea which fuse this should be?

[Bitter]

No, sorry. It's not a bad idea to just check all the fuses with a fuse tester. You should be able to jump the other two terminals and force the pump on, but that 7 volt reading is a little odd unless they're using a ballast resistor to drop voltage for the pump so it doesn't run full tilt all the time (like they do for the fuel pump).

[rhodesyboy]

Yeah it's odd but I think it just runs when you touch the throttle and then stays on for 30 seconds or so rather than varying how much it pumps so 7 volts is most likely a crappy earth or something, I'm not 100% certain on how it runs but I'm pretty sure thats it.

Yeah I jumped the two terminals and nothing, suppose there could be another crappy connection from the relay to the pump too but not 100% sure.