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Hey up.... I'm getting back in the garage and working out whats needed to sort my Capri.. Mojo has had a healthy boost from various sources - and I want to sieze it quickly whilst its here. The problem I had with the electric fan not kicking in we've discovered is because the standard thermostat switch in the bottom of the Audi 100 radiator (general VAG slag) is not designed to run 12v. So when it clicks its supposed to tell a relay to then tell the fan to come on - Id wired it straight to the fan and it seemingly burnt out the switch and therefore no fan. This is what the standard one looked like;  I could do the whole relay thing but I no longer have the original thermo switch as we disected it when trying to fault find. I already have an inline sensor for my aux temp gauge so blocking the hose and using an inline one is not an option. Is there such a thing as a thermo switch that will fit the hole in the bottom of the rad (M22x1.5) that can handle 12v? If so can someone point me in the direction of it as I'm not having much luck...   Thanks guys |
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Thermo switch helpBenzBoy
@benzboy
Club Retro Rides Member 7
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I wouldn't run a leccy fan without a relay - they draw a lot of current. You only need a regular 4-pin relay.
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hmm, that's interesting...
Is it just the VAG ones that are different?
I kinda though they were all much of a muchness... as I picked up a GM temp sensor for my Capri, but haven't fitted it yet.
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Thermo switch helpBenzBoy
@benzboy
Club Retro Rides Member 7
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I think that's the sort... I always just take 'em from scrap cars as I'm a cheapskate! ;D Here's a wiring diagram I found on t'interweb:  Use heavier wire for terminals 30 and 87 as that will be carrying the juice, with a 30A in-line fuse. The wiring through the switch doesn't carry much current as it's only used to activate the relay. That way you don't overload the switch.  I'm no expert on electrics - I struggle to get my head around it most of the time, but I've wired in an electric fan using a similar set-up to yours. |
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Awesome thanks so much mate uber useful ;D I've just put the car on axle stands for the next phase of the exhaust and I'm about to order my relay now shweet! Sarkie I'm not sure dude, I'm sure someone will know though? |
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mk2/mk3 polo swiches probably other vw's at the same time had them
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ChrisT
Club Retro Rides Member
Posts: 1,638
Club RR Member Number: 225
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Thermo switch helpChrisT
@christ
Club Retro Rides Member 225
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I thought most OEM thermoswitches would handle 12V, it's the current draw of the fan that they can't handle, which is why a relay is a must. guess you've learnt that now.
another thing to consider is the temperatures the switch operates at.
Befriend someone at your local motorfactors so you can sit with the parts catalogue looking through the thermoswitch section for one with the right thread and temp range.
Also, I like to have a manual override when fitting an electric fan, if the thermoswitch fails or for some reason you think the temp's too high you can always switch the fan on yourself. All you need is to run a switched +ve feed to terminal 86 as well as the other wire.
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Thermo switch helpBenzBoy
@benzboy
Club Retro Rides Member 7
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Yeah I found myself wishing I had a manual override in my car - I used a switch from a Fiesta OHV and whilst it kicked it soon enough, sometimes after long summer traffic jams things would start getting a bit warmer than they would with a viscous set-up. As ChrisT says, all fan switches run on 12v - it's the high ampage that killed the switch. |
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dungbug
Posted a lot
'Ooligan!
Posts: 2,852
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Good to see the mojo returning Davey.  |
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Past: 13 VW Beetles from 1967 - 1974
Bay Window Campers (1973 & 1974)
Mini's (1992 Cooper lookalike & 1984 '25 Anniversary)
MK2 Polo Coupe S (1984 & 1986)
MK2 Polo Breadvan (1981 & 1984)
MK4 Escort (1989)
MK2 Granada Based Hearse (seriously)
Fiat Uno 60S (1986) Punto 60S (1998) Cinq (1997)
1998 Yamaha YZF600R Thundercat
2003 Ford KA
Current: 2004 Ford Focus (barely alive)
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Thanks guys  really appreciated - manual overide is an excellent idea nice one - I would have just wished I had one in the future if you hadn't mentioned it ;D |
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ChrisT
Club Retro Rides Member
Posts: 1,638
Club RR Member Number: 225
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Thermo switch helpChrisT
@christ
Club Retro Rides Member 225
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I've also wired in a light to come on with the fan, although you can hear it anyway - just another 'safety feature', if the light comes on and the fan doesn't you know there's a problem.
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Rich
Club Retro Rides Member
Posts: 6,267 
Club RR Member Number: 160
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Thermo switch helpRich
@foxmcintyre
Club Retro Rides Member 160
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big-thread VAG switches should run directly into the fan with 12V, you must have just had a duff switch. At least all the ones I have ever seen did.. :/
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bortaf
Posted a lot
Posts: 4,549
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Most if not all of the late cars I work on have a realay, early fiestas didn't and it was a popular mod back in the day on RWD Xflows to swap in a FWD stat housing and switch to run a leccy fan but certainly every car i've worked on (post 80's) has a relay, the general way I tell is if the switch has small ternals it's relayed if it has the larger terminals like what the red and blue crimp femail terminals fit then it's a direct no relay type ?? BUT not allways, some manufacturers just like to over engineer things ?? relay is deffo better quite a few fans seize cos they sit unused for so long and personly i' like to keep the amount of 30 odd amp cable to a minimum, a large section burning out can make a right mess ! Pluss if your not using the same fan with the switch the fan could well be drawing more than the switch can handle, is it deffo a rad fan switch not an aircon secondary fan switch, they draw less so the sitches are less beefy ? |
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Last Edit: Feb 5, 2011 15:51:29 GMT by bortaf
R.I.P photobucket
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Yeah it's definatly a rad fan switch- I've ordered my new one and my mate has a relay for me I'll just run it with a manual over ride and an inline fuse - just gotta wait for the new switch to arrive I reckon it'll be here by next weekend fingers crossed
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really appreciated - manual overide is an excellent idea nice one - I would have just wished I had one in the future if you hadn't mentioned it ;D 
