FAN speed - No low speed

[merak_sissi]

Hello Fellas,

Another thread on fan speed which hopefully will fuel some good discussions and answers. since I owned my car I have been a little bit puzzled with the noise of the fan, finding it a bit load. But because the tempature regulation is flawless I never really bothered... until I had to chase some electrical issue (another post soon). This week end I started to investigate deeper the topic.

• I have an Autel scanner and used it to test the FAN in low and high speed. Relays tested, resistor too. All good. I can activate the the 2 modes low and high but the speed is exactly the same. Both mode operate in high speed. I even did the test by disconnecting the relay high speed when testing low speed and vice et versa.
• I started to worry about a wiring issue in my harness and decided to unwrap the harness going from the fuse box to the FANs... and found something interesting. Sorry for the poor sketch below but basically the wiring on my car is not following the drawing I found on this forum (4200 Engine fans question). The wiring looks genuine factory and now it explains why I have no low speed. Basically the resistor bridges the + of the 2 FANS. I checked 10 times as I could not believe it
• When the low speed relay is activated the passager FAN get the battery voltage and the driver FAN gets reduced current through the resistor. When the high speed relay is activted this is the opposite. Conclusion I have always 1 FAN running low and 1 running high...
• The diameter of the wires is the same for all, so no low speed smaller wires for example.

Anyone has observed the same on their car? My QP5 is a 4.7s. It was manufactured in summer 2010 and is a 2011 model.

 

[CatmanV2]

Have you checked the condition of the fan resistor....

C

 

[merak_sissi]

Yes I did, the resistor is ok and I have a spare one which gives the same resistance. Touching the resistor when the FANS operate it's getting warm.

 

[strictly]

Yes I did, the resistor is ok and I have a spare one which gives the same resistance. Touching the resistor when the FANS operate it's getting warm.

That's unusual. I have a wiring diagram for a GT and it looks to match the 4200 diagram where by the resistor is wired to both fans not one. See picture.

As I understand it the resistor controls the low speed from the low speed relay and operates both fans. High speed bypasses the resistor using the high speed relay

I understand your wiring does not look like this! What did you do?

I will be investigating my high and low speed fans (2011 GT) and whether both left and right are operating at the same speed in a couple of weeks.

My fans dont seem to be able to take the endine lower than 87 degrees C at idle, at 20 degrees ambient, with the AC off, and therefore the fans are not switching off unless I rev the engine to 2000 rpm which then brings the temperature down to 83 in 30 seconds.

I am going to explore the following

A. if my high speed works
B. If the ncm is commanding low and high speed
C. If the relays are sticking
D. If both left and right fans operates at the same speed
E. If my physical wiring matches the diagram.

I understand your problem is D and E and this is why you are scratching your head.

For me I may have a fan/wiring/relay/resistor issue or I may have also sticky thermostat or partial blockage in the radiator or etc. Before i looking at the liquid side I am going to look.at the electrical side much like you have.

 

[Oneball]

What colour are the wires directly connected to each fan?

 

[merak_sissi]

Thanks for the diagram. If you have more wiring diagrams on pdf files that you can share that would be great. Let me recap my case:
- I have not touched the harness myself. But clearly it's not wired as your diagram shows. I verified the wiring 10 time before drawing it (see picture above). The wires, splices... everything look profesionally done. So perhaps a previous owner did a good job or it's from factory.
- In the list of verifications I performed:
1- I tested the fuses and relay for low and high speed. All good.
2- I tested the activation of low and high speed with my autel OBD scanner. I even disconnected the high speed relay when I tested the low speed and vis et versa. All good.
3 - I verified the resistor and unplugged it. All good.
4 - Then I had no other option than checking the harness from the fuse box to the fan connection and this is how I figured out the incorrect wiring.
In your case I would check the resistance of the temperature sensor in the radiator and check if it's within specs. I don't have the numbers in mind but I remember when I bought the car I purchases on amazon a temparture sensor https://www.amazon.com/dp/B09ZY8GHFC?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2 and verified the others in the car. I did a test bench warming up water and connecting the 3 sensors to a Ohms meter. All were good, I had a lazy thermostat (which I tested later)

 

[merak_sissi]

What colour are the wires directly connected to each fan?

Red and black

 

[Oneball]

Red and black

According to the wiring diagram one of the power feeds should be red and the other fan should be black and red.

 

[strictly]

@merak_sissi

Ok good idea. I was thinking about testing the thermostat in water (warming up) but completely forgot about the temperature sensors. I will check that.

I will have a look at my wiring...but not for a couple of weeks. I know mine is a GT and yours is a QP5...but it would be intresting to see if it deviates from the diagram.

In terms of more resources...sure do. If you find anything we dont already have as a community have then please share so we can build a better technical library for all.

The wiring diagrams are at the very end of the 2011 to 2017 GT workshop manual. You will need to find m145 in the folder section. See pictures.

I don't think there are any wiring diagrams in the M139 section but there may be. The maserati academy section has some amazing information, im so grateful for maserati writing those documents to such a high standard of information.

https://drive.google.com/drive/fold...LMWh1aXc?resourcekey=0-BtbXAWXhAWrQS8cgCEkn8g

 

[merak_sissi]

@merak_sissi

Ok good idea. I was thinking about testing the thermostat in water (warming up) but completely forgot about the temperature sensors. I will check that.

I will have a look at my wiring...but not for a couple of weeks. I know mine is a GT and yours is a QP5...but it would be intresting to see if it deviates from the diagram.

In terms of more resources...sure do. If you find anything we dont already have as a community have then please share so we can build a better technical library for all.

The wiring diagrams are at the very end of the 2011 to 2017 GT workshop manual. You will need to find m145 in the folder section. See pictures.

I don't think there are any wiring diagrams in the M139 section but there may be. The maserati academy section has some amazing information, im so grateful for maserati writing those documents to such a high standard of information.

https://drive.google.com/drive/fold...LMWh1aXc?resourcekey=0-BtbXAWXhAWrQS8cgCEkn8g

This is awesome, I didn't had the GT documentation, thanks a lot!

 

[merak_sissi]

According to the wiring diagram one of the power feeds should be red and the other fan should be black and red.

Thanks, I didn't pay attention. I'll check again.

 

[strictly]

According to the wiring diagram one of the power feeds should be red and the other fan should be black and red.

Ah good work. I did not know how to read the colours. After your post I did a search and found this in our M139 section. It explains the wiring colours.

I see now that RN = Red Black