Cooling Fans running continously
#1
08-03-2016, 09:18 PM
Cooling Fans running continously
Hi, as it says in the title my electric fans were running all the time - I only noticed this today because I parked the car for 1/2 hour and when I returned, the fans were still going full blast. Not normal behavior!!
My first thought was that the fan relay had jammed closed so I scooped the spare one off the parts car and, just in case it was the rad sensor, I grabbed that too.
Trouble was that when I got home and switched her off, the fans stopped.
So it's sort of fixed itself
Try as I might I couldn't get them to stay on anymore ...I did give the driver's side fender a couple of whacks so maybe that freed up the "stuck" contacts ...however I think the situation may be temporary and if those fans DO stay on for any length of time it would make short shrift of my battery.
Of course the fan relay is in my least favourite place, under all the plastic crap near the carbon canister, but I guess I have to venture in there once again and swap it for the other one ..
BTW - anyone ever experienced a failed rad temp sensor?
Larry
My first thought was that the fan relay had jammed closed so I scooped the spare one off the parts car and, just in case it was the rad sensor, I grabbed that too.
Trouble was that when I got home and switched her off, the fans stopped.
So it's sort of fixed itself
Try as I might I couldn't get them to stay on anymore ...I did give the driver's side fender a couple of whacks so maybe that freed up the "stuck" contacts ...however I think the situation may be temporary and if those fans DO stay on for any length of time it would make short shrift of my battery.
Of course the fan relay is in my least favourite place, under all the plastic crap near the carbon canister, but I guess I have to venture in there once again and swap it for the other one ..
BTW - anyone ever experienced a failed rad temp sensor?
Larry
#2
08-03-2016, 09:40 PM
Member
I've experienced the opposite. I have one electric cooking fan (as far as I can see) right behind the grille and it never comes on, ever, and I wish it would. But I discovered in my fuse panel as I was checking the fuse for my starter solenoid that the slot for the fan had the wrong rated fuse, so I fixed it! Just waiting for a hot day to go drive it and see if it comes on. Hoping there's no defects in the circuit for the electric fan from having the wrong rated fuse for who knows how long..
#3
08-03-2016, 10:51 PM
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Hi Larry,
I haven't had this problem, but I was curious so I just took a look at the schematic. If I read it right, there are two relays in the Fan Control Relay Module, a main power relay that uses two contacts plus the two coil contacts, and the fan relay that uses five contacts plus the two coil contacts.
The radiator thermal switch can connect the main relay coil to ground to power the fans, but it also appears that the refrigerant pressure switch (single) and refrigerant pressure switch (triple or trinary) can also do so, so they would be additional suspects.
Cheers,
Don
I haven't had this problem, but I was curious so I just took a look at the schematic. If I read it right, there are two relays in the Fan Control Relay Module, a main power relay that uses two contacts plus the two coil contacts, and the fan relay that uses five contacts plus the two coil contacts.
The radiator thermal switch can connect the main relay coil to ground to power the fans, but it also appears that the refrigerant pressure switch (single) and refrigerant pressure switch (triple or trinary) can also do so, so they would be additional suspects.
Cheers,
Don
Last edited by Don B; 03-11-2017 at 02:22 PM.
#4
08-03-2016, 11:44 PM
Don - Thanks for the pointer to the trinary switch - I'll have a look at it tomorrow.
I just finished reading a LONG post on Jag-Lovers on the cooling fan issue(s) that Joe Umbertino had back in 2013 - Bryan N and Mike Stone eventually helped him figure it out but I learned a bunch about the operation from the thread too.
Bryan wrote this explanation:
and
Lots to digest but maybe of some help to the next owner who has cooling fan issues. BTW they were discussing a 94MY car.
Hopefully mine will clear up without too much headache!!
Cheers
Larry
I just finished reading a LONG post on Jag-Lovers on the cooling fan issue(s) that Joe Umbertino had back in 2013 - Bryan N and Mike Stone eventually helped him figure it out but I learned a bunch about the operation from the thread too.
Bryan wrote this explanation:
Here's the way I understand (in part) that the cooling fan system works.
If you select A/C then the A/C compressor relay is energised _and_ the 'trinary switch' in the A/C high pressure line is made so that both the compressor and the right (upper) cooling fan work _providing_ that there is adequate pressure in the A/C system (between 29 and 392 psi).
Similarly, with or without the A/C selected, if the A/C system pressure exceeds 392 psi, the relays (in the green relay module) governing the right (upper) and left (lower) cooling fans will energise to drive both fans.
Further, with the A/C selected (and the ignition 'ON'), if the A/C system pressure exceeds 218 psi as measured by the single pressure switch in the A/C system, a dedicated relay in the green fan control relay module will energise to drive the left (lower) cooling fan in isolation.
Even if the A/C is _not_ selected and the coolant temperature (as measured by the radiator thermal switch) exceeds 186º F, a dedicated relay in the green fan control
module will be energised to drive the left (lower) coolant fan, but that will switch off if the coolant temperature drops below 173º F.
However, if the coolant temperature exceeds 212º F, the relays in the green fan control relay module will all energise to switch on both the left (lower) and right (upper) fans.
If you select A/C then the A/C compressor relay is energised _and_ the 'trinary switch' in the A/C high pressure line is made so that both the compressor and the right (upper) cooling fan work _providing_ that there is adequate pressure in the A/C system (between 29 and 392 psi).
Similarly, with or without the A/C selected, if the A/C system pressure exceeds 392 psi, the relays (in the green relay module) governing the right (upper) and left (lower) cooling fans will energise to drive both fans.
Further, with the A/C selected (and the ignition 'ON'), if the A/C system pressure exceeds 218 psi as measured by the single pressure switch in the A/C system, a dedicated relay in the green fan control relay module will energise to drive the left (lower) cooling fan in isolation.
Even if the A/C is _not_ selected and the coolant temperature (as measured by the radiator thermal switch) exceeds 186º F, a dedicated relay in the green fan control
module will be energised to drive the left (lower) coolant fan, but that will switch off if the coolant temperature drops below 173º F.
However, if the coolant temperature exceeds 212º F, the relays in the green fan control relay module will all energise to switch on both the left (lower) and right (upper) fans.
The 'trinary switch', as it's name suggests, has three functions.
1) It energises the compressor clutch relay when the A/C pressure is between 29 and 392 psi if A/C is selected.
2) It de-energises the compressor clutch relay if the A/C pressure falls below 29 psi to [prevent damage to the compressor
3) It energises both relay elements in the fan control relay module if the A/C pressure exceeds 392 psi to drive BOTH the fans
So, it is NOT true to say that the upper right fan will run whenever A/C is selected.
I should have said that, providing that the coolant temperature does not exceed 212º F with A/C selected the upper right fan will only work if the A/C system pressure exceeds 392 psi.
1) It energises the compressor clutch relay when the A/C pressure is between 29 and 392 psi if A/C is selected.
2) It de-energises the compressor clutch relay if the A/C pressure falls below 29 psi to [prevent damage to the compressor
3) It energises both relay elements in the fan control relay module if the A/C pressure exceeds 392 psi to drive BOTH the fans
So, it is NOT true to say that the upper right fan will run whenever A/C is selected.
I should have said that, providing that the coolant temperature does not exceed 212º F with A/C selected the upper right fan will only work if the A/C system pressure exceeds 392 psi.
Hopefully mine will clear up without too much headache!!
Cheers
Larry
Last edited by Lawrence; 08-04-2016 at 09:58 AM.
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