Temperamental Fans

[KIN3595]

S3 v12 coupe. Right hand fan seemed to be sticking. Tried cleaning up and could get it going by spinning by hand but thought it wise to change the fan motor.
Changed over this weekend but even with new motor it doesn't always start spinning on its own. Sometimes it works sometimes it doesn't.
Checked and cleaned all electrical connections but no different.
The fan is on a manual switch rather than on automatic.
Once it's is spinning it doesn't cut out.

Anyone else had this problem or have any thoughts?

Best wishes

Simon

[KIN3595]

Think it might me a relay as it only one fan is having problems?

[mgcjag]

Hi Simon....dont have a S3 but yes there is a relay that operates them....do you have a wireing diagram...if not look in the knowledge base section under technical...all the manuals are there....then S3 electrical......and you will find a diagram http://www.myetype.co.uk/forum/viewtopic.php?f=16&t=700 hope ghis helps a bit..... come back if you still have problems you will get it solved here

[KIN3595]

Thanks Steve

I'll check the terminals on it, one good thing from looking at the diagrams is that I now know where they are!

Seems the most obvious

If not I'll buy a new one, they're only £20 from SNG

Cheers

[Yeldaw]

I am also having problems with one of the fans on my series 3, looking at the wiring diagram they both seem to work off the same thermostatic switch and therefore should come on and operate at the same time without any delay. Therefore my thinking is if one is n't working the problem will be either the relay, the wiring from the relay to the fan or the fan itself. Can someone confirm my understanding is correct and the fans should operate at the same time.

Thanks
Dave

[Heuer]

S3 Fan relay diagram (courtesy of Simon Stanton-Yeomans): http://dl.dropbox.com/u/8496016/S3%20Fan_Relays.pps

[MarekH]

Dear Dave,

Your understanding is correct.

You can confirm that for yourself by disconnecting the battery and the fans and checking the continuity of the wiring from one fan connector to the other. You should see that they are set up to operate in parallel. If not then the wiring has either been altered or is defective.

kind regards
Marek

[vee12eman]

Hi,

Sorry if there was a misunderstanding, but the wiring diagram shown is in fact designed to show my own, modified system, using two relays, rather than one. I bought a new relay (a replica of the original Lucas unit) it would come on when required, but the terminals welded together under the current and refused to separate. I was using modern fan motors as mine were missing; maybe they drew too much current. Anyway, I designed the circuit shown too and made the rather crudely drawn PowerPoint slide to prove to myself it worked. I later sent this to David to post and clearly did not make it obvious that the design was for a twin relay system.

(David, can I suggest you modify the original post with my drawing in to show that it is in fact a modification, sorry if I did not make it clear all those years ago?)

I felt two relays were better than one so that if one failed, at least one fan would run and I also used modern relays rather than the original design, partly because I had some available, partly because of my experience with the replica relay failing.

All this, does not help solve your problem, so here are some thoughts:

First, the correct diagram:



However, you say the fans are operating on a manual switch. If so, the diagram may be inaccurate for your system, but the switch is probably in the same place as the relay, at least, as far as the circuit goes.

As Marek says, the fans operate in parallel, supplied from one relay (switch). Therefore, if one fan is working, the relay is operating, or in your case, the switch. (It is possible the switch has internal issues, dependent on the design, I can't comment further without seeing it).

So I think it likely your problem is the wiring, the connections or the motor itself. The motor could be lazy, for example the brushes on the point of wearing out, just enough to make a contact sometimes and keep the motor running, but perhaps not always to start it. Alternatively, the wiring inside the motor may be suspect. (edit, just noticed that you changed the motor, so ignore the last)

Whilst the wiring connections may be clean (as you cleaned them yourself), the wire may not in fact be making a good contact with the contact(s), due to being loose in the crimp or, more likely, corrosion in the tail of the connector(s). The wire itself may be breaking down inside its insulation. All of these can happen after 40 plus years of being located in an area which can be hot, soaked with salt water from the roads, or both at the same time, for prolonged periods. In my own case, I built my own wiring loom, hence the circuit diagram I drew to prove the system to myself.

Multi-meter tests will help, but rather than just relying on simple connection tests (usually with a "beep test"), check the resistance of the cables and connectors - often there is enough current flow for a beep test to work, but a resistance to full flow, this is usually associated with corrosion. Don't forget to test the earthing, which is often overlooked and taken for granted.

Finally, auto is better than manual when working correctly, although the original switch can be temperamental, so I suggest you get a modern sensor and the correct housing for this (Mike at Coolcat is the best source), re-install the relay (preferably a modern or well tested original one) and replace the wiring. I'm pretty sure you can buy a complete fan loom from someone like Autosparks, or you can make your own.

Hope this may help,

Regards,

[Yeldaw]

Thanks for explaining the dual relay setup, I was getting confused because mine has a single relay. If both fans work off the same terminal on the relay the issue must be with the fan or the wiring. I will get the multi meter out and see if I can track down the problem. I noticed on the coolcat website they recommend using the six blade fans off a VW Jetta/ Golf so if the fan is problem I may trying fitting these at the same time.

[Heuer]

This is the diagram I had intended to post rather than Simon's dual relay modification:
S3 Fan wiring diagram (animated): https://dl.dropboxusercontent.com/u/748 ... rcuit.ppsm

The link was just below the modded diagram in the Forum KB.

[helge.kassel]

Hi David, just looked at the Dropbox-link and get an ERRROR-message.