I have is situation where the fans on my XJ8 are not activating.. they will not activate with the A/C or at normal operating temps under any circumstances. I went through a bunch of posts and could not find an issue quite like mine.

I replaced the busted fan assemblies with two new (used) fans
Tested each fan, both work
Fuse 12 was missing, replaced
Fuse 14 was blown, also replaced
Tested fan relay, operating as it should
Temp gauge is registering halfway as it should.

It seems the ECM is not sending a signal to the fan relay to activate the fans. the three internal solenoids in the relay sit open unless i apply a jumper then the fans will kick on in the different speeds depending on where I apply the jumper. It seems I am just missing a signal from the ECM?

What might cause this? Thanks for the help.

 

Have you tried to actually repalce the radiator fan Control module? From what i can see from the drawing is that i contains atleast two diodes.. if one or both of them has burned out im sure you would get problems.


According to the electrical drawing the ECM control signals has a plug/joint somewhere on the way to the control module, if found, it should be fairly easy to measure the signals from the ECM in order to see what is going and alternatively provide a ground on each lead in order to checkrun the fans with all relays and fuses in place..


Ensure that all grounds involved is ok and that, since fans are backed upp with 30A fuses; nothing has overheated. I have a few times come across contaktpins/tabs that has overheated in such a way that they sort of let go of its maiting part.. you will not see it when you pull the contact apart or the relay out from its socket unless you look really Close up.


/E

 

Is the AC working? It could be the pressure switch. If leaking you would not get a signal to the fans.

 

I will check Einhead's suggestions on Friday, I work 24 hour shift work Wed-Thurs. The A/C seems to be working, compressor engages and it has a charge. I cannot verify charge pressure as my gauges are in Missouri ATM and I am in California. I will get some gauges and verify pressure switch operation Friday.

Thanks for the help so far.

 

Maybe also check the coolant temp sensor is working, they do fail.