Technical Radiator fan not working

Currently reading:
Technical Radiator fan not working

slowmk2

New member
Joined
Jun 8, 2022
Messages
23
Location
London
hello, this forum has helped me alot while working on my fiat and i need a little help on where to start first. After the new engine was fitted and running ive only realised now that i don't think the radiator fan has ever come on yet, i let my engine get up to temp [till the needle was just halfway] and still nothing, after that i disconnected the coolant temp sensor and the fan did not come on. I then inspected the wiring and seems to be okay, fuses look fine, but i wasn't sure which relay was for the fan, anyway i read you can connect a 12v power supply to test the fan, how do you do this?

also I'd like to add that my lower radiator hose would not get hot, the top one will but not the bottom. The top hose also feels quite squishy but im not sure what im looking at and if that's an issue

thankyou!

Kins
 
OP
OP
slowmk2

slowmk2

New member
Joined
Jun 8, 2022
Messages
23
Location
London
update: managed to wire up the fan to battery, and it works fine, swapped the relays and tried unplugging coolant sensor with engine running and still nothing
 
Joined
Jan 11, 2015
Messages
2,127
Location
Helsinki
update: managed to wire up the fan to battery, and it works fine, swapped the relays and tried unplugging coolant sensor with engine running and still nothing
the fan relay is the large one so you cannot swap it with the other relays. If you remove the relay and connect the two large connectors in the fusebox the fan should work
 
OP
OP
slowmk2

slowmk2

New member
Joined
Jun 8, 2022
Messages
23
Location
London
the fan relay is the large one so you cannot swap it with the other relays. If you remove the relay and connect the two large connectors in the fusebox the fan should work
so am i missing a fuse?
 

Attachments

  • 20221104_142033.jpg
    20221104_142033.jpg
    1.3 MB · Views: 14
OP
OP
slowmk2

slowmk2

New member
Joined
Jun 8, 2022
Messages
23
Location
London
Ok. I led you astray a bit. But i think your car should have a relay in position 6 for the radiator fan. I suppose only the cars with air conditioning have the large relay in position
That's what I am thinking, i don't really understand this much but from what i can see here is the engine cooling fan even without air con has a relay at the bottom of fuse box [R6]?
 

Attachments

  • 16676718482805765527105008889101.jpg
    16676718482805765527105008889101.jpg
    847.8 KB · Views: 13
OP
OP
slowmk2

slowmk2

New member
Joined
Jun 8, 2022
Messages
23
Location
London
That's what I am thinking, i don't really understand this much but from what i can see here is the engine cooling fan even without air con has a relay at the bottom of fuse box [R6]?
ignore that, someone marked the fuses wrong, R6 is the red relay at the top left im pretty sure :)
 
Joined
Nov 23, 2005
Messages
3,036
Location
Wexford
The ECU earths the fan relay via a little grey wire that runs from below the fusebox to the ecu plugs. If it gets broken as mine did you will have the symptoms you have. A test is to lift the fan relay a little, get a wire in at the earth pin, ground it somewhere handy with the temp sensor disconnected and now does the fan run.
The pin is 85 if I'm not mistaken and it runs to B8 on the ECU, our 2001 Mk2. Another way is just test that wire for continuity. The break was at a bend in the harness about midway between the fusebox and the ECU.
When you disconnect the temperature sender you should get a red flag on the dash and a slight increase in idle speed. Then you know the car is reacting to the 'missing' sensor and it's just lost sight of the fan relay.
 
Last edited:

Mike1alike

Active member
Joined
Aug 3, 2017
Messages
445
Location
Timisoara
And for the lower radiator hose not getting hot (and most probably no heat inside the car), here is a real fix that I've done and the heat is still working great in my car:
 
Top