Installing a Fan Override Switch on a Chim

[SNT]

Hi all,

I'm thinking of installing a fan override switch on my 99 Chim. The fans come on at 92 degs and keeps the temp there broadly there when stationary, but I do some town driving and want the peace of mind of being able to switch the fans on if (when) I hit some really nasty traffic.

There is a write-up on Chimaera pages which suggests that it is relatively straightfoward. The problem is that I don't understand any of it!

I'm a newbie trying to slowly work my up the DYI chain. Just to give you an example, I'm quite chuffed that I managed to install a Hot Start Kit without destroying anything. So don't assume any knowledge of anything on my part...just patience and (I hope) some common sense.

So two questions:

1) does anyone have clear instructions on how to install a fan override switch, ideally with nice pretty pictures?
2) is it really a DIY job for the novice DIYer like me (please say yes)?


Thanks a lot for your help.

S

[scotty_d]

I fitted one very cheap and easy and proved very well to work as i just did over 3000mile round europe in middle of summer.


All i did was add a length of double core wire and a toggle switch which is in parallel with the otter switch which brings them on when ever i want and can keep them on as long as i want. cost less than £5 and took less than a hour to fit.

[spend]

Just finding the Green/pink wire going into the fusebox and switching it to ground seems a lot easier to me.

[JonRB]

I had one on mine. Then subsequently fitted the lower temperature thermostat and otter switch and never needed it again. Which makes me conclude that a fan override switch is simply a sticking plaster / pain-killer solution.

[scotty_d]

JonRB said:

I had one on mine. Then subsequently fitted the lower temperature thermostat and otter switch and never needed it again. Which makes me conclude that a fan override switch is simply a sticking plaster / pain-killer solution.

Disadvantage to that is i can keep the fans on all the time which was really good when in town in Europe/traffic or tolls when very hot and thus keep the heat out the cockpit unlike the thermostat and otter kicking in and out. kept the car at around 70-80 degrees if i left the otter to do its job would sit at 90ish.


The lower temp thermostat in winter is not ideal as the cars run cold anyway when on the move in low temperatures.

Edited by scotty_d on Monday 24th August 21:40

[SNT]

Thanks for the advice.

I was contemplating changing the otter switch and thermostat. Some of the mail order companies don't clearly state whether the otter switches they sell are the higher or lower temperature models. Could you point me in the right direction?

Cheers

S

[scotty_d]

spend said:

Just finding the Green/pink wire going into the fusebox and switching it to ground seems a lot easier to me.

Access to the fuse box is never easy never mind the back of it

[Ant.]

scotty_d said:

spend said:

Just finding the Green/pink wire going into the fusebox and switching it to ground seems a lot easier to me.

Access to the fuse box is never easy never mind the back of it

In that case, find the same wire as it comes through the bulkhead and T it off to another switch around the steering wheel.

[winters]

scotty_d said:

The lower temp thermostat in winter is not ideal as the cars run cold anyway when on the move in low temperatures.

Hopefully not taking this too off-topic: Just wondering what you consider to be running cold? The lower temp. thermostat was something I was seriously considering, after I read in SH bible that the higher temp was fitted again to later Chims/Griffs (of which my car is one), and the rolling road chaps at last year's Chim Roar commented on how much more power/torque I had when running cooler. I guess this is a fairly complex topic. How do people with the lower temp stat & 'newer'-model chim/grif find the cooling in icy conditions and clear runs?

Back on point, regardless of how you get it done the fan override is great for peace of mind IMO. I'm so much more comfortable to be sitting in traffic at a very-near-constant 80 degrees rather than at a wandering 90-100 wondering if it might blow its load (yes, I realise it shouldn't - and never has except when the serp belt snapped quietly )

Edited to add: I think 70-80 (though not sure how/where measured) is the target temp right? Do people find it can run lower with the lower temp stat - or is it just taking a long time to hit temp? Cheers.

Edited by winters on Tuesday 25th August 08:54

[Andy JB]

Not sure why you would want to do this if your engine/fans are running correctly?

The thermostats job is to cut in at a certain temperature to cool the engine via fans when it exceeds defined temp. If you are worried it may be getting too hot its far cheaper and effective to install a lower temp thermostat (leven do one) which cuts ion automatically than instal a manual overide.

If you have a rad/fan problem it may be better to fix the problem than apply a temp solution IMO

[cloggy]

When I had my Griff 500 there was an override switch linked to the button that was intended for the dashboard lights on/off at your left knee.

[JonRB]

scotty_d said:

Disadvantage to that is i can keep the fans on all the time which was really good when in town in Europe/traffic or tolls when very hot and thus keep the heat out the cockpit unlike the thermostat and otter kicking in and out. kept the car at around 70-80 degrees if i left the otter to do its job would sit at 90ish.

Whatever you say; I'm not going to argue. All I know is that I never needed to use my fan override switch again after the lower temperature otter and themostat were fitted, and the car happily ran for years like that up to (and as far as I am aware beyond) the day I sold it.

[scotty_d]

A manual fan can ease comfort in the car in hot climates ie Europe in the middle of summer my car ran spot on over 3000 miles in temps around 35 degrees out side temp.

Problems with TVR's is fiberglass which is a great Insulator thus making the car hot under the bonnet when not moving.

So all this heat where does it go when not moving in to our cockpits it will follow the best heat transfer route IE any metal. What is next to your left leg a great big metal gear box carrying lots of heat making us pretty uncomfortable in very hot days.

Its all very well fitting a lower thermostat in summer but in winter your car will run near stone cold not allowing the oil to get up to temp.
For me it is not a quick fix just my reason behind it, it is rarely used in the UK but is handy just to know it is there as a second measure. And it is still cheaper for a length of wire and a toggle switch than buying a thermostat.


My rant over

[spend]

Its a lot easier to switch the fans on if your otter switch fails... Press of a button vs getting out the car, fiddling under the bonnet to insert a fuse instead of the otter switch,keeping wires away from twirly bits, cleaning hands, cleaning suit +tie +trousers + muddy shoes, explaining why you arrive late, wet, bedraggled,foul tempered......

[JonRB]

scotty_d said:

Its all very well fitting a lower thermostat in summer but in winter your car will run near stone cold not allowing the oil to get up to temp.

Wait... what? A thermostat that opens at a certain temperature will prevent an engine from coming up to temperature? WTF?

This was simply not my experience when my Chimaera had both a lower temperature thermostat / otter switch and a fan override switch. The engine got up to 80 degC and then simply stayed there. The switch was never needed.

I'm sorry to go on about this, but I honestly do believe that a fan override switch is merely a workaround solution to an underlying problem. And I know I am not alone in that belief.
Fit one if you want. Fit five; I don't really care to be honest.

spend said:

Its a lot easier to switch the fans on if your otter switch fails... Press of a button vs getting out the car, fiddling under the bonnet to insert a fuse instead of the otter switch,keeping wires away from twirly bits, cleaning hands, cleaning suit +tie +trousers + muddy shoes, explaining why you arrive late, wet, bedraggled,foul tempered......

Ok, I will happily concede that point.

Edited by JonRB on Tuesday 25th August 14:21

[winters]

My override was fitted under previous owner, by Fernhurst, is a new button on the steering column by ignition.

So has anyone actually HAD bad experience of the lower temp thermostat (and or otter) in the winter - on Alpine runs etc??

Does any one know why TVR fitted the higher temp ones back on the newer cars? Only ones available at the time? Or was there a proper reason - e.g. Scotty's suggestion of bad winter behaviour?

Edited to add: Override was also 'nice' the other week hammering round Rockingham in the hot sun. Temperatures were pushing up - a lot higher than running temps on the road, so I left it turned on permanently so I was pre-cooling while messing about in the pits/garages and left it blowing under the bonnet while the car was parked up on cool-downs. How much this really helped, I won't know. Didn't see any other cars overheating. But I guess it could have helped on an even hotter day.

Edited by winters on Tuesday 25th August 14:31

Edited by winters on Tuesday 25th August 14:32

[spend]

IMHO otter switch makes little difference to the winter cooling problem.. Yes 2 stage & early switches replicate a little more the original RV8 viscous fan, but that only really affects the hot balanced cooling to stop/crawl surge scenario. Location of the otter switch also makes lots of differences, due to hot surges in swirl pot the later positioning in rad makes much better sense - particularly in return side :smug: - think of it like having your home hot water stat in the cold feed to the immersion tank The otter switch is not programmable to take account of all loads & conditions, you can actually do a lot smarter calcs in the human brain and press the over-ride BUTTON

The standard thermostats still flow when closed, otherwise you would have even bigger nightmare air locks and bleeding problems. In cold conditions on the move (wind chill?) this is enough to keep the engine under 70C. The only real solution I found was to put in a different stat if I wanted to drive in wintery conditions (don't bother anymore as cold tyres aren't any fun anyway )

[zippy500]

Easy peasy job. Simple on/off toggle switch from Maplins, and a metere and a half of 2 core cable.

Piggyback of otter switch wires, poke cable through wing at Throttle cable entry point, stick under dash somewhere convienent to you. I choose inside the steering wheel shroud with swith facing towards pedals, so totally out of sight.

I'd much rather be in control of the cooling arranegments personally and this is a cheap and reliable method.

[scotty_d]

zippy500 said:

Easy peasy job. Simple on/off toggle switch from Maplins, and a metere and a half of 2 core cable.

Piggyback of otter switch wires, poke cable through wing at Throttle cable entry point, stick under dash somewhere convienent to you. I choose inside the steering wheel shroud with swith facing towards pedals, so totally out of sight.

I'd much rather be in control of the cooling arranegments personally and this is a cheap and reliable method.

+1 that all i was getting at.

[SNT]

Thanks for all the comments.

Great to see how a fan switch can stir up emotions!

I am sold on the fan override switch idea. I do a lot of continental driving (because I live in France) and drive in town which means the engine gets hot (between 90-95) but I've never been stuck in a really bad jam so I just want peace of mind.

Zippy500 (or anyone else), any chance of some photos so I don't mess anything up (remember, I'm new to this).

Thanks again.

S