Series 3 V12 Running Hot

[Heuer]

Mike

If you have time please photo document the installation and post your instructions/photos in the 'Upgrades' forum. I am sure it will be of value to other S3 owners.

[SESH]

Will do David.
It's off for a bare metal re-paint next week, so I will use the opportunity of getting it done whilst the bonnet is off. I am going to photo record the whole process anyway so will include photos of the VW fan replacement.
Mike

[SESH]

The Coolcats radiator fan conversion has been done! http://www.coolcatcorp.com/V12Fan/V12Fans.html We did it slightly differently from the coolcats suggested method - I will explain later. The fans were purchased new from Ebay at the cost of about ?28.00 each. They are VW motors for the Jetta or Golf Cab. The motors are a superb fit in the existing mounting cradle and the fans fit exactly inside the existing radiator fan shroud. Now you get two six blade modern fans instead of old tech four blade. Plus you have a manual overide to a two speed fan which draws a huge amount of air through the rad when needed on a hot day or when in heavy traffic. The high speed manual connection is made through the spare rocker switch on the right of the dash that was originally intended for the heated rear window on the FHC. Mine is an OTS. However, we did make a couple of changes to the coolcats design. When we wired up the two fans in tandem it kept blowing the fuse (50 amp) and the wires were getting hot when high speed mode was selected. We found that each motor was drawing 26 amps at high speed. Therefore to overcome this we re-wired each fan seperately each with its own dedicated fuse. Fortunately the spare rocker switch on the dash allows for two connections. In addition to make it a bit safer and not put the full ampage through the switch we wired in two relays, one for each circuit. Plus on top of this I got the rad re-cored with a high efficiecy core allowing 20% more cooling with additional cooling veins. So hopefully we should have a cool cat. !! Mike.

[SESH]

I am trying to upload some photos of the coolcats fan installation.

[Loyer]

I added a manual toggle switch to be able to turn on the fans with the flip of the switch.
On a series 3, a terminal on the relay above the radiator can be grounded by wiring through a $5.00 rocker switch mounted next to the radio (silver thumb screw).
I did this last year and find myself using the manual fan switch often.

Also, "water wetter" helps a lot.

[SESH]

Good to hear it is working well. I will invest in some water wetter as well. Although I have also had the radiator re-cored with a high efficiecy core with 20% more cooling veins. Fortunately for me with my car being an OTS the rocker switch on the main panel - right hand side is redundant. So we wired the high speed fan up to that switch via a couple of relays. How long ago was your Fan mod done and has it always been reliable?
Mike

[Nialls Shortbear]

Here's my wiring diagram for the 2 speed coolcats job
Cheers

[Ole-xke1974]

That looks a lot like my diagram, except that I wasn’t sure if I needed a relay for each high speed feed and also not having the low speed feed connected to the fans, but through the high speed relay so it is disconnected from the low speed terminals when running high speed.
I also have a two step switch for overriding the thermostat and switching on the high speed fans.
I have measured that the current draw for high speed operation is at the upper end of what my relays are rated for and may use two like you have.
I may post my diagram, when I find it.

[42south]

Hi
I’ve also done the coolcat mod and very happy with it. My suggestions are
Replace the Otter switch with cool cats modern temp sender mod. It uses a nice alloy fitting to replace the otter switch steel one, with a modern Porsche switch, reliable and readily available.
Don’t use tired old Lucas relays, recipe for more failures. Use modern Bosch solid state relays, they look quite good on top of the fan shroud, and are reliable.
Cheers

[Nialls Shortbear]

Gents;

I agree about the coolcat switch instead of otter, we are using that too with the housing they sell. I find it comes on a little before the Otter i.e. slightly lower output radiator temp.

I used two relays for high speed because of the other comments on this thread about the current draw, as corroborated above here again.

I am doing a complete wiring diagram for S3 in colour from which this was an excerpt, as I think there are numerous errors and missing items on the one bandied about generally which is based on the service manual. When I get it done I will upload to knowledge base.

I think you are probably correct about the relays however we are still using the Lucas jobs, as I have not been able to bring myself to use a modern variant as yet. They just don't look the part, so we drive round with a box full of Lucas ones.

Cheers
NS

[42south]

Hi
I don’t reckon the modern relays look too bad, ok not a shiny tin case,but, with the shroud installed they are not even visible.

[Nialls Shortbear]

Yeah there's not much in it, and you are of course right about the cowling! Doh!

relays 2.jpg (100.8 KiB) Viewed 9475 times

[42south]

Thats a very nice job you are doing on your radiator area.
I may have to modify my relay setup to yours, as I have only got one relay for both fans on high speed, and thanks to another poster I found out the amperage draw is way above the relay rating.
Cheers

[42south]

I’m now confused about the current draw of the fans on high speed setting.

Ole posted some figures quite a while ago that showed each fan drawing 12.2 amps on high, so a combined total of 24.4amps was within my 30amp relay.

Since then another poster came up with a much higher figure, well over the 30amp mark.
The formula of watts/volts = amps 250/12=20.83amps per fan.

Am I missing something, do I need to change my relay, or split the fans to a separate relay for each.
Cheers
Mark

[rossco_j]

Hello Mark,
I've attached some photos of my findings using the fans recommended by Coolcat (Audi/VW). The current was measured using a Fluke meter & is for one fan.

[42south]

Thanks Rosco
That’s a relief, I didn’t want to change things. I’ve been running like this for several years with no problems.
Regards
Mark

[rossco_j]

I should have added that there maybe an initial turn on spike but your setup should be fine.

[Nialls Shortbear]

Thanks Mark,

I should add that I posted that photo more in the relay oriented conversation as it doesn't show the coolcat 2 speed install, that' a different car. But yes I was also going by the much higher current draw figures posted here when I designed my coolcat wiring, hence the diagram above with more relays, I thought it was high enough to warrant one each for the high and a common for the low speed with a control relay.

Thanks to the other for confirming the currents, much lower than reported, I'll measure my own on the bench before deciding the final wiring.