SP5 Horizontal water temperature sensor

hindsight

Whilst doing some maintenance, I just spotted something that I've never noticed previously. I have a water temperature sensor on the water union on the horizontal cylinder. Checking the SP5 parts fiche, it looks like this is standard (but I don't recall it on any of my previous pre-'93 machines, and I don't recall it on my '94 916).

Trouble is - it has a lot of wire connected to it (looks suspiciously like it might have been wired by a previous owner), but isn't actually connected to anything. Where is this normally wired to?

Does anyone have a SP5 wiring diagram?

Thanks,
Mike

Jasper

Here you go.

hindsight

Thanks jasper - will come in handy for sure, but unfortunately it doesn't have this connection on it - perhaps this temperature switch/sensor is indeed specific to the sp5

Mike

Jasper

Are you on about this one?

hindsight

Yes - exactly that one, highlighted in red

Where does your connection go? - I'm guessing that it's a secondary fan switch control, so will likely head in the direction of the fan. A previous owner installed a manual fan switch on mine, connected to the loom at the temperature switch by the radiator neck. I suspect he may have been planning on connecting this in somewhere also, but never completed the work.

brad black

that's the sender for the dash gauge.

hindsight

Really? - I must be confused somehow - because, although I've not used the bike much in the last few years, the temperature gauge was definitely working when I ran it just a few weeks ago. More cable tracing required.

Oh - and I've got to the bottom of the charging problem I mentioned a while back. complete new alternator (stator/rotor) on it's way to me.

Jasper

hindsight wroteReally? - I must be confused somehow - because, although I've not used the bike much in the last few years, the temperature gauge was definitely working when I ran it just a few weeks ago. More cable tracing required. Oh - and I've got to the bottom of the charging problem I mentioned a while back. complete new alternator (stator/rotor) on it's way to me.

What is the issue you are having?

hindsight

Right - I've got a handle on this now. I wasn't going quite as mad as I thought.

The water temperature sender is indeed disconnected, but the temperature gauge does indeed work like I thought - because a previous owner reconfigured it, with the water temperature connection (Orange/Black wire) now connected to an oil temperature sensor installed into the sump, near the gauze filter. The gauge is therefore reading the oil temperature and not the water temperature.

I guess it was the obviously non-standard wiring of the water temperature sender that was catching my attention, but it's the oil temperature sender that appears to be unusual (or at least, most other sumps that I recall looking at - have it blanked off).

The bike has been running fine in this regard, but I guess I do need to keep a careful eye on the cooling system.

brad black

none of the water cooled bikes have oil temp sensors. the oil temp tends to rise much slower, altho it'll be better on a water cooled bike than an air cooled one.

hindsight

brad black wrotenone of the water cooled bikes have oil temp sensors. the oil temp tends to rise much slower, altho it'll be better on a water cooled bike than an air cooled one.

This one does! 😉

I was thinking further about this last night. The water temperature sensor looks different to normal, so I suspect the former owner swapped it out, with the intent of connecting a separate gauge or alternate dash. I think I'll put a normal one in, and relocate the cable back to measuring the water temperature. I suspect it's more important to be monitoring the coolant temperature, than the oil temperature - for exactly the reason you suggest - it'll rise quicker and any problem will show itself sooner.