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Radiator fan kicks in as soon as the car starts


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If you have air conditioning and it is switched on, then the fan will run from the moment you turn the key. if you turn off the AC then the fan should stop until required to cool the engine.

 

It runs with the AC to cool the condenser otherwise you would not get cold air in the cabin for very long.

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No, I am not using the AC system. It is always off. So there must be a reason why the fan kicks in. Maybe bad wiring? Maybe the lack of thermostat? Maybe a bad fuse? Another detail is that the fan is running at high speed, always. Is that right?

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check the connections at the radiator, make sure they are ok and bridge them when the engine is off and see if the fan comes on. it cant be a bad fuse because it wouldnt work at all and the horn and headlight flash are on the same circuit so you wouldnt have those too.  

 

i cant see why a lack of thermostat will make a fan to run all the time, mine didnt do that when i had no thermostat.

 

how much has the car been yours? has it done it from the day you bought it? or recently when you described the overheating issue?

 

only problem i see is with the coolant temperature sensor sending false readings to the ecu, and the ecu is thinking that the engine is hot all the time

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only problem i see is with the coolant temperature sensor sending false readings to the ecu, and the ecu is thinking that the engine is hot all the time

That would be impossible.  His Felicia has a carburettor.

 

check the connections at the radiator, make sure they are ok and bridge them when the engine is off and see if the fan comes on.

That test is useless. He already knows the fan is working.

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Unplug the radiator thermoswitch. If the fan now doesn't come on from the start, replace thermoswitch. 

I am sure the fan won't come on from the start that way. In fact I am sure the fan will never work with the thermoswitch disconnected :) I assume you think the thermoswitch has fused contacts on high speed.  That can't be the case because the fan would run all the time, key off included. Look at the wiring diagram below.

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I am sure the fan won't come on from the start that way. In fact I am sure the fan will never work with the thermoswitch disconnected :)I assume you think the thermoswitch has fused contacts on high speed.  That can't be the case because the fan would run all the time, key off included. Look at the wiring diagram below.

 

You're right about the bit in green, I now see thanks to your diagram. :)

Disagree with the bit in red though. It looks to me like either relay J101 (fan will run at high speed) or J229 (low speed) can bring the fan on without the thermoswitch connected even. Either 'properly' by their coils being energised or - more likely I think here - by their contacts being welded closed.  Measuring continuity on the (unplugged) J229 or J101 relay pins 2-8 would rule in/out the latter.

 

Actually, no, I have to disagree with myself! Welded closed contacts would be 24/7 fan running just like shorted thermoswitch contacts.

Must be either relay J101 pin 4 being high when it shouldn't (F129 faulty)? Or J229 pin 6 being high when it shouldn't be.

 

As the OP says it's running at high speed, that implicates J101, so if he unplugs the connector from F129 pressure switch, it should fix the problem unless there's a wiring short somewhere taking that blue wire to 12V, I think? Or just unplug J101, come to think of it.

Edited by Wino
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You are spot on with your diagnose. I didn't elaborate further on schematics because I had to deal with an urgent case of seized Felicia gearbox for a customer. I had also strong doubts that the wiring and the A/C electronics of ObedP's car are OK. If you look at ObedP's gallery / slides you'll understand why. It's one of those OMG projects because the car looks like it was vandalized then submerged in mud for years. If he will restore it to its former glory, he deserves the "Felicia owner of the year" medal :)

Edited by RicardoM
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:D  "Felicia owner of the year" medal...that's a good idea! In deed that must be a pinned topic for someone that success with a DIY project. Thank you Jonnycila for your support. Thanks Ricardo for your investigation and thank you Wino for the diagnose. I have a lot of work to do this weekend: check the radiator fan contacts, check if I have thermostat, and check why the tachometer isn't working. I love this place!!! 

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