A/C auxillary fan

[Testie]

I finally manage to fit an auxillary fan into my 1974 SL350. Although I have the Haynes workshop manual with the wiring diagram I have a few questions.
The wire that pulls the compressor clutch in appears to go across the car, and without removing all the tape that binds the wiring loom, disappears.
Simple enough to run a wire from the compressor to a new relay with a new power supply wire so that whenever the air con. is "on" the fan is "on".
Also this can be controled by adding temp. sensor and maybe a timer. Not nessassary?
Question. is there a relay fitted already? does it live in the front near the radiator? If not, what does the relay fitted there do?
Silly questions but I don't want to add more relays if , as the wiring diagram shows, there is one already fitted.

 

[WGB]

I have had my 450 and my 6.9 converted to H134a and in both cases the auxillary fan was re-wired via a relay so trhat it comes on every time teh compressor clutch is pulled in.

Apparently this is normal with H134a conversions due to the higher temps this gas runs at.

When my 450 was converted I did not know the original wiring setup and so the A-C firm fitted a new fan and wired it in direct from the battery with an extra relay sited near the RH side of the radiator. I later found the original relay in the driver's footwell had suffered water ingress and was not working.

When I rebuilt my 6.9 system I was a bit more cogniscant of the design and the original power supply was included in the design but again the fan comes on when the compressor is pulled in as well as leaving the original temperature controlled system working as a backup.

Bill

 

[Testie]

Thanks for the reply Bill I will try to wire it up this week. Work commitments' keep me away quite a lot but thats life.
Col.