Hi all, complete newbie to the forum...
Im trying to diagnose a radiator fan problem on my S40 2.0d R-Design, I have disconnected the 3 pin plug that feeds the fan control module and put my meter across the main power and have 12v output (the larger pins), I also have a reading of 4.38v from the remote (the smaller pin) Does anyone know if the remote pin should read 12v upon fan activation?
Ive been so tempted to cut the purple remote wire and add a 12v feed to the fan control unit to see if the fan kicks in but thought id seek some advice before doing this.
note:- the Control module and fan appear to be hard-wired, so I cant directly test the motor without cutting the wires.

 

The fan control on the Volvos uses a pulsed power line to power the fan. I don't recall the specifics, but you'll get a reading of something under full battery voltage if you use an analog (needle-style) voltmeter. Using a digital meter might work, might not... depending on how it interprets a square wave signal.

You should be able to disconnect the fan motor to test it. There should be a plug on the upper right side of the radiator (as you're looking at it, standing in front of the car). I don't have the wiring diagram but that should be easily google-able so you'll know which lines to put power on to test).

 

yes it was this plug that I took the readings from using a digital meter, I take it the ECU must send a signal to the fan control module then, which points to the module being at fault, I was expecting to get an increased reading from the remote pin as the engine temp increased to where additional cooling is required.

testing the fan directly doesn't really help matters as the module is part of the fan assembly and not an individual part, all the wires are fixed in place without any connectors other than the one you mentioned, the 12v feed was already there plus the 4.38v.
I can only presume my next step is to get a computer on it and see if theres any fault codes.
Cheers

 

Here's a post I did on the subject (a V70 fan, but the concept should be the same)…
https://volvoforums.com/forum/2001-2...hen-hot-77389/

Here's the relevant part about measuring the voltage on the control wire (with an analog voltmeter)… "The good thing is that I figured out that you CAN kinda/sorta see the fan being commanded to come on (or not) by reading the purple wire with an analog voltmeter. Figure about 1.5VDC for full on, 5.5VDC for 50%, 8.5VDC for 25%, and battery voltage for off. "

 

I didn't see any change in output </> .01 volt on the purple wire, as the engine ran
I keep seeing issues regarding aircon causing the fan not to work as well?... my aircon needs regassing

 

Rob, I ran into the same thing with my V70 - the fan wasn't kicking on when the A/C was engaged, but I only later figured out that if the system is low on gas, it's not going to kick on the radiator fan(s). I was also surprised by the fact that the radiator fans don't come on until the coolant hit 105°C (that's well over boiling - 221°F). Might be different on the S40 / V50 (don't have my VIDA working yet to check).

Speaking of which - this is one of those situations where having a VIDA / DICE system would be very helpful, since you could command the fan to come on at any "speed" you like, which would give you a very easy trouble-shooting task.

 

Got home from work and pondered more about the situation, decided to get a temperature probe, got the cars temp needle up to halfway, took the expansion cap off and tested the coolant temp with the car running idle for well over 15mins and was still only reading 85c...decided to get in car and burned my back on the leather! Ran a medium idle for a few more mins, went back to test the coolant temp and still only 95c, but this was already starting to drop as the car went back to normal idle.
Outdoor temp was reading 29c....basically got fed up of burning myself in the sunshine (and in the car) so gave up !
Trust me the only thing keeping its cool was the engine.

Anyway im calling over to see a relative who's got Vida so gunna give the car a once over and set the fan to come on from 95c for a little more peace of mind... I got a feeling theres nothing wrong with it, so the money saved will pay for a re-gas.