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Discussion Starter #1
hello, have had an ongoing prob with our 806 1.9td 1998 in that the radiator cooling fans are running constantly, even b4 starting the engine. sofar have got by with just pulling the fuse so disabling the fans, but would like to sort this. have been advised that most likely culprit is the radiator fan switch, this is stocked by ecp and shows in the peter russek book. however have spent the whole day trying to locate it, its meant to be under the bottom hose but no sign. i tried tracing the wires from the fans but no luck. in desparation i've taken the complete fan assembly out of the car which gives all round access to the radiator, still no sign of the pesky fan switch. i did notice the radiator looked in quite good condition for an 18yr old car. we've owned the car for 9 years and never changed it so am thinking it was changed b4 us for a pattern part that has no fan switch but surely there would still be wires from the fans for the old radiator switch. have found a strange looking sensor that fits in the fan housing at the top with the words "roche moreau pierrelaye with the number 17 stamped in the middle, one end goes to a brown block connector grouped with the other radiator fan wires, the other end has 2 wires going to a black housing holding a silver sensor- any ideas as 2 what this is and with the above would be much appreciated- one good note i finally found the crank angle sensor so hope changing this will solve the hot starting prob
 

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Discussion Starter #3
806 rad fan switch

hi citrail, thanks for prompt reply. i've just been out to car and checked and where your switch is in your photo is just plastic moulding on mine altho the rest looks similar ie the bottom drain plug- the sticker on the rad says valeo 838567D, as for the crank sensor its just beneath and behind the fuel filter housing about 5cm to the left of the gear change linkage- hope your not going to tell me its the wrong one- i've undone it from the block - the end of the sensor is magnetised and looks similar to the one on the euro car parts site, thanks again
 

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Yes it's a crank sensor but think it only controls the rev counter, could be wrong tho.

I've just bought a brand new valeo rad, it came with a plastic bung in the hole for the fan switch.
If yours hasn't got the fan switch fitted, then there should be the plug and wires somewhere.

I'll nip out and have a quick look at one of mine and see where they go.
 

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Arh, does your car have aircon?

My Roland Garros does and doesn't have the fan switch where my other does (as in photo)
As I understand it, the fans come on constant when the AC is switched on, where the temp sender is I've no idea. :-(
 

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On AC versions there should be a separate control box for the fans like the 406 had but cooling fan also had a sensor on the thermostat housing to tell the box it was hot.

There are many variations in the circuits though.
 

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Discussion Starter #7
806 fan switch

hi citrail thanks again for the help, yes ours does have aircon its an eden park. as i said i've took the complete fan housing out, all the wires go to a plastic housing with detachable lid at the top, 3 block connectors i think, these then go off to a loom under the n/s headlight- as far as i can see there are no other wires or sensors coming out of the rad. I've also heard that both fans come on when starting the engine but although the aircon is turned off the fan keeps running. this was causing difficulty with cold starting during winter, so i've pulled the aircon fuse disabling the fans. cold starting is now back to first turn of the key- its wierd tho as ecp does list radiator switch for both aircon/non aircon versions, but as i say with the fans and the air filter housing removed i can see all around the rad, unless i'm going blind there's no sign of any other wiring. I'd like to know what the sensor is with the number 17 stamped on it is for, its secured by 2 screws into the top of the cowling with the sensor end facing but not touching the rad
as for the crank sensor ecp has an offer on at the mo so its worth a punt to cure the hot starting prob
 

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Discussion Starter #8
806 rad fan switch

hi reliable 406, just seen your post. on our 806 thermostaat housing there are 2 coolant sensors i think, one has a blue housing the other brown, have never known why it has two, not sure if its worth replacing these, thanks for the advice
 

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hi reliable 406, just seen your post. on our 806 thermostaat housing there are 2 coolant sensors i think, one has a blue housing the other brown, have never known why it has two, not sure if its worth replacing these, thanks for the advice
Think these are for the temp gauge on the dash
 

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Discussion Starter #11
will try first thing 2mrw, as an aside have you had your roland garos long? these cars seem to be getting rarer- so practial tho, ours is 18yrs old,had it for 9years, hoping to get another 6yrs out of it
 

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Cant remember the colours now but there can be 3 sensors on thermostat housing 1 is for coolant temp gauge 1 is for fan control 1 is stop light on dash for overheat warning i think its been a while :)

The blue one should be single wire and is coolant sensor for fan control and if unplugged the fans stay running so if sensor was open circuit fans would also stay running
 

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will try first thing 2mrw, as an aside have you had your roland garos long? these cars seem to be getting rarer- so practial tho, ours is 18yrs old,had it for 9years, hoping to get another 6yrs out of it
Only just bought this one. Had a Ulysse for 7 years before and only cost me a set of rear brake shoes as one of the linings came off due to a weeping cylinder, plus tyres of course.

Having a new windscreen fitted on Friday then it should be ready for MOT before the end of month.
 

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Discussion Starter #14
806 rad fan switch

thanks reliable 406, got the blue sensor on order for pm 2day altho the parts man was a bit sceptical, for less than a tenner worth a try.
citrail, i disconnected the crank sensor from the block and fired the old girl up, the rev counter still worked- getting a new one this pm to try, thanks again to both of you for help
 

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There are 2 sensors on the front of the t/stat housing, the one for the fans is the one on the right with the brown plug, the one on the left with the blue plug is the coolant dash light sensor.
 

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Discussion Starter #17
806 rad fan switch

hi xudpug, thanks for info, i changed the blue one today at the front of the thermostat with no change to problem,have sprayed all contacts with electric cleaner.i did change the brown one next to it 2years ago with a cheap one off ebay.(and managed to over tighten it in its thread). i found another one behind the housing, any idea what thats for? also just found the throttle cable fraying, gawds sake what next....
 

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Discussion Starter #20
no prob reliable406, grateful for any input, will see if i can get last sensor 2mrw, have hopefully got mobile mechanic coming on friday to change throttle cable (looks a right pig of a job), so will ask him to maybe run some tests. thats presuming he doesn't turn round and drive off when he sees where the cable is routed ......
 
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