I have an electric fan I was wanting to add in front of the radiator for extra cooling, can I draw power off the ignition coil area and thus get power that comes on with the engine. and where ever power comes from do I need a resistor or some 'pre fan' device on the way to the fan itself.?

 

NO.

Some do, I do NOT. Leave the ignition as just that. Your car, your choice eventually.

To use that PRE resistor power wire (12V) to switch a relay would MAYBE be acceptable.

I ran a seperate Ign Power wire from inside the cabin on all our S2 cars.

That way I knew that there were no add on thingies to the ignition system at all. Then, when the Prince of Darkness struck, I was only dealing with what that circuit was designed for.

 

I agree with Grant, for he same reasons, leave the ignition system alone. There must be some other key-switched power source in the engine bay somewhere!

If you absolutely must tap into the ignition voltage supply then use a relay. That is, use your key-on supply voltage to the coil to trigger a relay.....which only take a few mili amps ....which in turn powers-up a new circuit using battery voltage from another location

Actually, a relay is a good idea for most *any* added circuit IMHO

Cheers
DD

 

If you are having cooling issues check the basics first. Thermostat, fan, coolant level, ignition timing, etc. If timing is retarded the engine will run hot. You may want to remove the radiator and flush it clean, often sediment can build up at the base and restrict coolant flow. Often debris can collect between the radiator and A/C condenser that will limit air flow too.

If you do need extra cooling capacity for some unusual reason... retrofit a Series 3 fan, radiator and thermo-coupler from a later model.

Typically front mounted pusher fans are used for supplemental cooling for the A/C condenser and are wired to run with the compressor clutch or using a pressure switch and relay harness.

 

Reviving this thread as I'm looking for ideas for a switched power source in the engine bay of my SIII. I mounted a new fan controller on the passenger side of the bay (LHD) not far from the battery and need to connect a switched power wire. Any ideas before I get out the test light and start looking around. Would one of the prongs on the starter relay be an option?

Or, there is a small hole to pass a wire into the cabin at the top of the passenger footwell. If I do that, where do you recommend tapping into a switched source? Thanks.

 

Hi Winston, you have obviously been researching your topic among former threads. That's commendable but let me try to explain why it is poor practice to rekindle an old thread.

Firstly, it is highly likely that all the former contributors have moved on and will be unlikely to respond to your query. Secondly, and all too often, a new contributor to an old, long silent thread, may THINK they have a similar issue, but the causes or, in your case, answers may be entirely different. Thirdly and finally, grafting your new question onto an old problem may well skew other contributors to past answers, past knowledge, and fail to take advantage of more recently acquired knowledge.

Best advice is to encourage you to post a new thread. If you wish, include links to old threads that you think have some bearing on your issue. That said, let me offer some advice to better get you started. First, arm yourself with the relevant electrical diagram . . . Sticky section here or Gus' JagRepair.com . . . and pay particular attention to whether your MY uses switching between the fused power feeds and devices (old style architecture), or switching in the ground seeking area beyond devices (modern architecture).

Best wishes,

Ken