Technical Radiator fan using a lot of electricity

[Cristian97]

Hello, I have an issue with the Barchetta, the model is from 1997, it doesn't have AC it's with just with one fan on the radiator. The issue appears when the thermostat sends the signal to the fan to turn on. The moment when the fan turns the rev start to go wild it doesn't stay in a stable point, like between 800-1000 rpm, and I need to rev it to keep the engine going, if not the engine will stall and this happens while driving to so its not good. So I checked the relay, the thermostat is new, and the temp sensor was changed recently, I checked the relay and the cables for it and I found this which was weird for me so could someone confirm if this is correct, like one of the wires from the relay goes to a point and then it splits into two wires. Is that oem or it was modified, and did someone else have this issue with the revs like the fan consumes to much electricity and the alternator can't keep up?Thank you.

 

[s130]

That Y joint looks standard according to the "B" wiring diagrams. Under the tape is what Fiat call a N.D connections. This is a welded joint.

From the relay the a single wire colour BV and a the weld/joint splits into two wires. On BV and one AV. Both go to the Hitachi engine ECU. AV goes to ECU connector C Pin 10 and BV to ECU connector C Pin 9. Both of these wires after the joint are used to energise the fan relay.

With no aircon then 9 and 10 are effectively connected together. With aircon then two fans are fitted to the car with 9 going to one and 10 to the other and there is NO Y joint.

 

[s130]

As for the engine rpm changing the I suspect it is not that the fan is drawing too much current but you may have a poor or missing earth connection so the current drawing is affecting the signals going to the ECU. Probably the throttle position sensor?

 

[Cristian97]

Hey s130. So you suggest to check the earth connection for the throttle position sensor, it was just interesting when i disconnected the fan speed relay the car would go back to normal? At the minute the car is out till Sunday but i will check

 

[Cristian97]

And i should mention that the air filter is a sport type. Could that make the idle wrong ?

 

[s130]

And i should mention that the air filter is a sport type. Could that make the idle wrong ?

I would think not. At idle the engine only requires a little air. Under power much more. The fact that the cars idles and runs under power OK and the problem only happens when the fan cuts in suggest it is all fan related.

As you say the revs oscillate between 800 & 1000 odd rpm then the ECU is trying to keep a normal 850-900 rpm and would appear to rev to 1000 then over cut back totally closing the idle control valve and stalling the engine?????

On the Fiat Tempra 1.8ie there was an Air Bypass (air loop around the throttle plate) and you could adjust this. At the factory it was set too low so the engine could stall. One had to set it so that the engine revs would never fall below 850 rpm even if the ECU commanded to do so.

Maybe??? the throttle body butterfly bottom position is incorrect? So we have engine idling normally till the fan cuts in. This draws 30Amps from alternator thus loading the engine. Revs drops so ECU opens the idle control valve, revs increase to 1000 and ECU closes valve to lower revs but throttle plate is over closed and engine stalls?

You can download the Barchetta workshop manual here:

https://www.fiatforum.com/downloads/categories/barchetta.11/

See what info you can find on the throttle body.

 

[s130]

I've just looked at the "B" Service manual, Engine - Page 58, and it does have idle adjustment and idle/bypass valve.

 

[Cristian97]

Update on the car I played a bit with the THROTTLE CONTROL CABLE and set the rpm a bit higher and now the oscillation looks that disappeared. But will keep this updated tomorrow i will take it out for a spin and will let everyone know if this is the fix.