Technical Radiator fan not kicking in

[NiekUntamed]

Hi fellow Panda owners and hopefully some experts too.

I recently bought a relatively well looked after Fiat Panda Dynamic 2006 model with known overheating issue.

I really thought it was going to be a quick fix and that I would be on the road enjoying the cat by now. I was mistaken. The radiator fan switches on when triggered manually at the relay and the temperature guage works correctly, but the fan does not trigger even when reaching 100 degrees celcius.

I have replaced the resistor with a good used one with no change. Checked all fuses, relays and wires and everything is in good condition.

I need to know if my resistor wires were connected correctly(Black and Red wire at the top and Light Blue wire at the bottom).

Alsp if anyone can confirm if this system works on a normally closed relay circuit and if any other internal electrical issue in the motor may cause this issue even though it spins when triggered.

Attached is an example of the type of fuse box I have in my vehicle.

Any help will be appreciated.

 

[koalar]

I take it got air conditioning

Makes no difference which way round the wires are

There's two separate circuits fans low fans high the controlled by different relays and fuses, also controlled by different wires from the ECU


If you fool the temperature sensor to put the fans on high do this work work

Koalar random thoughts | FIAT Panda (Mk3)

You can tell if the coil pack is getting a control signal and giving a good spark like this If one is weeker and the spark does not jump as far than the others it's suspect It is possible to get a jolt if you do something wrong, probably not a good idea if you have a pace maker As long as the...

www.fiatforum.com

Or switch the fan relays manually with bidirectional software

 

[NiekUntamed]

Thank you for your response.

I don't have a/c, but for a different reason. I replaced the condensor and haven't been able to get the system regassed. Will this affect the fans ability to work when the car runs hot?

I haven't tried fooling the resistor, only swopping it out with a different one.

Any other ideas will be welcomed and anything is helpful at this stage.

 

[koalar]

I don't have a/c, but for a different reason. I replaced the condensor and haven't been able to get the system regassed. Will this affect the fans ability to work when the car runs hot?

No, but the fan is wired differently on cars with A/C as the A/C also controlled the fan independently

The fan switches on when the temperature exceeds 95°C (1st speed) and 105°C (2nd speed).

The coolant sensor resistance lower as the temperature increases at
0C 5975 ohms
100C 176 ohms

We need to know if only 1st speed is failing or both


Putting a 100 ohm across the two pins of the coolant sensor should put the gauge at max and put the fans on 2nd speed

 

[NiekUntamed]

Thank you. Let me try that. Can you offer any insight regarding the relay? My red relay for the fan is normally closed and all the ones I have found online and at my local Fiat parts supply shop is normally open. That will make a big difference. Are you perhaps able to share a picture of the Red relay?

Your help is appreciated.

 

[koalar]

Both relays, different sizes

Are permently feed by battery voltage on both the control side and power sides

Both are normally open

The control side is ground side switched by the ECU

When the control side has a path to ground the relay closes and powers the fan

Are you sure your measuring the correct pins as if the relay is closed the fan would be on permently

There other identical relays to compare against

 

[NiekUntamed]

Once I plug in the relay it makes all four wires positive. Upon inspecting the diagram on the side of the relay I noticed that it was a normally closed relay. That is why I think the fan isn't switching on. As the line that is suppose to be a negative trigger from the ecu becomes positive the moment I plug in the relay.

 

[koalar]

Once I plug in the relay it makes all four wires positive. Upon inspecting the diagram on the side of the relay I noticed that it was a normally closed relay. That is why I think the fan isn't switching on. As the line that is suppose to be a negative trigger from the ecu becomes positive the moment I plug in the relay.

That is correct it's just a coil that bridges both sides

The wire going to the ECU should be floating at battery voltage all the time with the relay in and the engine cold

 

[NiekUntamed]

So the wiring is correct then. On to the next. I will do the resistor bridge on the sensor and take it from there. Not sure what els can play a role in the fan not triggering through the ecu and giving error codes.

 

[NiekUntamed]

That is correct it's just a coil that bridges both sides

The wire going to the ECU should be floating at battery voltage all the time with the relay in and the engine cold

I saw on another thread that I can use a potentiometer to better immitate engine temp. Any idea what spec I can buy? They have so many different ratings and I am not well versed with electronics.

 

[koalar]

Do you have a normal test ligh with a bulb like this

 

[NiekUntamed]

Do you have a normal test ligh with a bulb like this


View attachment 465857

Yes I do.

 

[NiekUntamed]

Yes I do.

Well. I have a cheap Chinese one that gives me a red light for postive and green light for Negative. Or maybe the other way around. Not just a single globe. I think it uses leds.

 

[koalar]

Shame LED ones will not work to activate anything as they allow very little current flow

Disconnect the coolant sensor

Switch the engine on and short across the two pins with a paper clip

The fans and the engine check light should come on

 

[NiekUntamed]

Let me do that once I get home. I appreciate your feedback.

 

[koalar]

Let me do that once I get home. I appreciate your feedback.

If you can pick up a test light as per photo I would do so, most of the pound shops around here in the UK sell them, as will as motor accessory shops

The test is the same but if you short with the test light it limits the current, so much safer and better way, I have short them myself on my own panda and nothing bad happened,

Also if need we can use it to activate the fan relays manually

Coolant sensor on your car isn't easy to get to

It's at the back right of the engine block if you are stood In front of the car

 

[NiekUntamed]

I unplugged the temp sensor wire and fooled the guage to believe the car is overheating, but still fans won't kick in. Testing at the trigger wire still gives me positive 12v at that temp. Bridging the relay still kicks the fan in.

 

[koalar]

Great so with the sensor bridged the gauge is reading max

Is this correct

 

[NiekUntamed]

Yes it is. With the engine light on as you said it will. Still no fan trigger or positive at the fan plug. Almost like the ecu is not able to trigger.

 

[koalar]

Yes it is. With the engine light on as you said it will. Still no fan trigger or positive at the fan plug. Almost like the ecu is not able to trigger.

Correct

Did you manage to get a test light