Cooling Fan Issue

[ORB 227 1 Cars]

First up, I better do the obglitory 'I have done a search' quote. . . .

 

 

I am aware of how the fan system works on a GTi - it is but a simple beast, but mine decided not to work last week and the engine got all hot and bothered. It has not ran since.

 

So, today I took the slam pannel and the grille off and had a poke about.

 

First up, I suspected the temp switch, so I put a bit of wire across the terminals of the plug and tried to get it to cut in. No, but I could get a relay to click on and off within the bay (in a black box near the battery)

 

So, I figured that I best move on to the resistor thingie. I could not find it. All my GTi's in the past have had one for the dim dip and one for the cooling fan. I found the Dim Dip unit under the headlight as per usuall but could not find the one for the fan, then it dawned on me, does my car have one?

 

It is twin fanned as standard and is an AC model. Does this mean I have a different set up to a standard GTI?

 

What would you do next?

 

Also, my bloody Horn stopped working, If I put a wire from the spade terminal to the battery it sounds. But I have no power at the wire. Fuses are all good so I am confused as it is normally an earth problem with the horn?

 

 

Thanks

[welshpug 1,666]

you are right there that a twin fan setup has relays not a resistor, it'll be like a TD arrangement.

 

low speed supplies the fans inline, and high speed supplies them both directly.

 

not sure of the arrangement in a 205 of relays, there'd be at least two.

 

 

if its a 1.9 then that will have a relay for the horn too, do you have power at the fuse and either side of the relay? good earth for the relay?

[ORB 227 1 Cars]

Thanks for that Mr Pug!

 

Very helpful indeed. Does anyone else have any pearls of wisdom for me? Just so I have all bases covered when I attack it again tonight?

 

Does the clicking of the relay tell you anything to aid my diagnosis?

 

Thanks

[petert 601]

There are three relays controlling two fans, switched by the radiator thermo switch which has three terminals. Depending on whether you have a Motronic car or a Jetronic car, depends on whether the relays are switched to earth or +12V. I have a wiring diagram for the Motronic setup, but easily re-interpreted for Jetronic. When two of the terminals are connected the fans will go to low speed (in series). When all three terminals are connected the fans are connected in parallel (fast). Brilliant setup!

 

So first thing to do is remove the connector off the thermo switch and bridge out the three wires.

[ORB 227 1 Cars]

Cool, thanks for that Peter, for your info, my car is NOT plastic inlet manifold.

 

Do you mean connect all three pins together, or one to another at a time?

 

Thanks again

[ORB 227 1 Cars]

Hmm, pair of relays bot been 'repaired' in the past. Changed one as I had only one spare and now I have a fan that comes on full bore with not slow speed!

 

I will get a new relay tomorrow and clean up the 'repair' (it looks like a spiders web in the relay box)

 

Thanks

 

Now to look at the horn! Am I correct in thinking that the horn is th ethird relay in the box??

[dee205 3]

No. The box of relays are for the fans only. I've just removed the setup from a diesel model to put in my Mi16. It's gonna be a matter of following the wires back to see what you find.

[petert 601]

It can still have an alloy manifold an be Motronic. Is the thermo switch on the inlet or outlet side of the radiator? Attached is the wiring diagram from a 405. It's the same for a 205. The only differences being whether the relays are triggered to earth or by +12V. The wire numbers are the same. There should be three relays, not two. As in M733, M733A and M733B. In this situation, the relays are turned on by the computer grounding wire 58 and 58A/58B.

 

Your setup may differ, in having the relays permenantly grounded and the thermo switch supplying +12V to the relays by the other two wires.

Edited June 5, 2010 by petert

[ORB 227 1 Cars]

All fixed now thanks, both Relays required swapping!

 

Now, the Horn relay, where would I find that?