Fan/air Con Failure

[Guest devacom]

My S3 n/a had been in storage for a while, and when I started up for the first time in weeks everything seemed in order except for fans and air con.

Neither the cabin fans nor radiator fans work, and the air con clutch doesn't operate when I turn it on. All fuses look OK so what's failed?

Answers on a postcard to....

[Evil_Dr_Fish]

Im just about to replace the fans on mine (they went a bit awol in an accident! - see "photopost" thread!) and Geoff at Esprit Engineering has recommended replacing them with the fans from an Elise - they mount directly to the rad (three individual ones too) as apparently the "gallery" of fans is renound for cracking, and more commonly seizing which MAY be what has happened to yours?

Do they turn freely by hand? Try connecting the powered connector directly to live (check it won't blow thme first - tho unlikely imo) see if they run like that?

Failing that, if you're not in too much of a hurry, call Geoff at Esprit Engineering when you're here and ask his advice?

01725 514449

HTH

Robin

[Guest devacom]

Thanks Evil! The radiator fans move freely, and I'll try connecting them directly, but my hunch is that the fault lies elsewhere as the air con and cabin fan also stopped working at the same time.

[Evil_Dr_Fish]

A relay perhaps?

Be careful connecting them up directly - I'm 99% certain they're 12v but best to make sure!

[Esprit2]

Use a voltmeter or test light to double check for 12v at the fuse. Even if the fuse isn't blown, there can be corrosion/ continuity problems that keep the circuit open. Remove the fuse, clean all terminals on the fuse and in the box.

Cycle the ignition swtich on-off several times in case the internal contacts are corroded. With the ignition switch in the Run position (or the engine running), do the radiator fans turn on if you short the two wires at the Otter switch together?

The ventilation fans are powered from the fuse panel via two orange wires... one for each motor. From the motors, two slate and two yellow wires go to the speed control switch.

The radiator fans are powered by an unfused, direct brown wire from the battery cable connection at the starter solenoid. The circuit is switched on-off by a power relay. In early cars, the relay includes an a fuse... check it. Later cars replace the fuse with a thermal trip.

The power relay is triggered/energized by low current wires from the Otter switch and ACU control switch. A low current wire from the ACU switch does trip the radiator fan relay to turn on the fans whenever the AC is switched on; but other than that, the ventilation and radiator fans are on separate power circuits.

Except... power for the low current Otter switch circuit that trips the radiator fan power relay comes from the same fuse that feeds the ventilation fan circuit.

For all of the fans (radiator and ventilation) to fail simultaneously after storage implies something in common failed. That doesn't preclude to separate but coincidental failures, but the odds against that are higher. In this case, the fuse, the continuity of it's connection in the fuse box, or no power feed to the fuse from the ignition switch would be the only elements both circuits have in common. From that point downstream the power circuits are separate. Clean all the fuse box terminals and install a new fuse (just to be sure).

The radiator fan relay may be contributing to the failure in that circuit, but it has nothing to do with the ventilation fans not working.

Good luck,

Tim Engel

[Guest devacom]

Thanks Tim, electrics are not my strong point but I'll work through your suggestions. Watch this space!

[delands]

If anyone knows where I can obtain replacement interior cabin fans or just even the motors.... then please post a reply

[Evil_Dr_Fish]

What about breakers? Boss Motors, South West Lotus just got a knackered salvage, Douglas Valley.

SJ Sports cars? Paul Matty?