Db7 Vantage : unable to trigger the cooling fans ON
Discussion
Hello everyone!
being quite disapointed to be unable to drive the car without checking the temp constantly and tired to short circuit wires so have the fans running, I'm here to read any of you who will have ideas to solve my issue.
So... It is an Aston Martin Db7 Vantage from 99, manual gearbox. I swaped engine since the original one died in the hands of the previous owner.
I never reached to make the fans run by themselves : whatever the AC switches are turned on, the coolant temp and the driving conditions, they just stay asleep.
I replaced the Fan Controller Module : no change.
I replaced the coolant temp sender : no change.
I checked every fuses, replaced the ones that are related to the fans management system : no change.
I tried to check for teared harnesses without any suspicious find
The only way I found to trigger the fans is the short circuit the fan controller module plug, or manually operating the relays inside the controller.
I read every topics I found about ford V6 of the era and XJ8 that shares a lot of parts and management logic, without any chance sadly.
So... Any ideas?
Some pics :
The coolant temp sender
The fan controller module
The plug of the FCM, I usually trigger the fans by short circuiting the largest poles together
The fuse boxes. The fuses related to the fans and management are located into the left fuse box
The Engine management should send signal to the FCM through the blue and white & blue wires
Cooland temp read through OBD with the sender plugged in
Cooland temp read through OBD with the sender unplugged
Cooland temp read through OBD with the sender plug short circuited (I now know that even a fully fonctionning DB7 cannot trigger fans with ignition on and engine off with this trick)
Any help would be really appreciated!
Cheers
being quite disapointed to be unable to drive the car without checking the temp constantly and tired to short circuit wires so have the fans running, I'm here to read any of you who will have ideas to solve my issue.
So... It is an Aston Martin Db7 Vantage from 99, manual gearbox. I swaped engine since the original one died in the hands of the previous owner.
I never reached to make the fans run by themselves : whatever the AC switches are turned on, the coolant temp and the driving conditions, they just stay asleep.
I replaced the Fan Controller Module : no change.
I replaced the coolant temp sender : no change.
I checked every fuses, replaced the ones that are related to the fans management system : no change.
I tried to check for teared harnesses without any suspicious find
The only way I found to trigger the fans is the short circuit the fan controller module plug, or manually operating the relays inside the controller.
I read every topics I found about ford V6 of the era and XJ8 that shares a lot of parts and management logic, without any chance sadly.
So... Any ideas?
Some pics :
The coolant temp sender
The fan controller module
The plug of the FCM, I usually trigger the fans by short circuiting the largest poles together
The fuse boxes. The fuses related to the fans and management are located into the left fuse box
The Engine management should send signal to the FCM through the blue and white & blue wires
Cooland temp read through OBD with the sender plugged in
Cooland temp read through OBD with the sender unplugged
Cooland temp read through OBD with the sender plug short circuited (I now know that even a fully fonctionning DB7 cannot trigger fans with ignition on and engine off with this trick)
Any help would be really appreciated!
Cheers
Bridging the plug proves the fans work and there is power to them. The temp of -40c when disconnected is correct, that is the default reading for a failed or disconnected sender. The temp shown in the other picture is 31c (?).
Fan 1 comes on at 93c and off at 90c. Fan 2 comes on at 105c and off at 100c.
I do not understand what the problem is. Is the engine overheating? Is the thermostat working properly? Once the temp reaches around 88c then the thermostat will be open and the top radiator hose will slowly get hot to the touch. The bottom hose will start to warm up as hot coolant flows through the radiator.
Connect the diagnostic tool and watch the temperature. Check it against the figures (taken from the manual) above.
Fan 1 comes on at 93c and off at 90c. Fan 2 comes on at 105c and off at 100c.
I do not understand what the problem is. Is the engine overheating? Is the thermostat working properly? Once the temp reaches around 88c then the thermostat will be open and the top radiator hose will slowly get hot to the touch. The bottom hose will start to warm up as hot coolant flows through the radiator.
Connect the diagnostic tool and watch the temperature. Check it against the figures (taken from the manual) above.
N7GTX said:
Bridging the plug proves the fans work and there is power to them. The temp of -40c when disconnected is correct, that is the default reading for a failed or disconnected sender. The temp shown in the other picture is 31c (?).
Fan 1 comes on at 93c and off at 90c. Fan 2 comes on at 105c and off at 100c.
I do not understand what the problem is. Is the engine overheating? Is the thermostat working properly? Once the temp reaches around 88c then the thermostat will be open and the top radiator hose will slowly get hot to the touch. The bottom hose will start to warm up as hot coolant flows through the radiator.
Connect the diagnostic tool and watch the temperature. Check it against the figures (taken from the manual) above.
If I just let the stock fan controller module, yes, it will overheat due to the fans not running at all. Fan 1 comes on at 93c and off at 90c. Fan 2 comes on at 105c and off at 100c.
I do not understand what the problem is. Is the engine overheating? Is the thermostat working properly? Once the temp reaches around 88c then the thermostat will be open and the top radiator hose will slowly get hot to the touch. The bottom hose will start to warm up as hot coolant flows through the radiator.
Connect the diagnostic tool and watch the temperature. Check it against the figures (taken from the manual) above.
I replaced the thermostat and the radiator is brand new. I can drive the car as much as I want if I can maintain a good air flow (meaning speed over 30 mph)
The coolant circuit is working fine.
The only issue is that the engine controller module doesn't seem to send signal to the fan controller module.
Looking at the plug for the FCM there is a blue/white wire. If this is definitely the signal wire then with the temperature cool, test this wire for voltage. Expect 0 volts. Once the temperature gets up to around 95c or above you should get voltage - either 5 volts or 12 volts - from the engine control module (ECM). If you do not then test the wire at the ECM pin. If still nothing then suspect the ECM and have it bench tested.
If you do get voltage here but nothing at the plug then test the wire for continuity. Or simply use a length of wire and bridge from the ECM to the FCM if you do not have access to a multimeter.
Can your diagnostic tool not actuate the fans?
If you do get voltage here but nothing at the plug then test the wire for continuity. Or simply use a length of wire and bridge from the ECM to the FCM if you do not have access to a multimeter.
Can your diagnostic tool not actuate the fans?
Edited by N7GTX on Tuesday 2nd June 09:55
N7GTX said:
Looking at the plug for the FCM there is a blue/white wire. If this is definitely the signal wire then with the temperature cool, test this wire for voltage. Expect 0 volts. Once the temperature gets up to around 95c or above you should get voltage - either 5 volts or 12 volts - from the engine control module (ECM). If you do not then test the wire at the ECM pin. If still nothing then suspect the ECM and have it bench tested.
If you do get voltage here but nothing at the plug then test the wire for continuity. Or simply use a length of wire and bridge from the ECM to the FCM if you do not have access to a multimeter.
Can your diagnostic tool not actuate the fans?
It seems that only the Aston diagnosis tool can actuate fans on demand. That would be quite clever in my case but I can't get on easily. If you do get voltage here but nothing at the plug then test the wire for continuity. Or simply use a length of wire and bridge from the ECM to the FCM if you do not have access to a multimeter.
Can your diagnostic tool not actuate the fans?
Edited by N7GTX on Tuesday 2nd June 09:55
I will definetely check for continuity to begin with : I'll come back to you as soon as I tested that.
thank you!
Looks like we made a huge progress!
I tested every wire continuity and it is all perfect.
I decided to redo a real test with a running engine.
Voltages were as expected on the fan controller module (12v when cold, then dropping when reaching target temp).
I plugged the OBD reader in this situation and saw that the instrument binnacle told be a different rear from the OBD. I took the risk to continue and trust the obd value then at 99° fans finally ran... I immediatly shutted off the engine because I want to be sure that the instrument sensor is over estimating temp and not the engine management receiving an under estimated value (the instrument never read near the red line however).
I buy a new instrument temp sensor and then it will be sorted !
I tested every wire continuity and it is all perfect.
I decided to redo a real test with a running engine.
Voltages were as expected on the fan controller module (12v when cold, then dropping when reaching target temp).
I plugged the OBD reader in this situation and saw that the instrument binnacle told be a different rear from the OBD. I took the risk to continue and trust the obd value then at 99° fans finally ran... I immediatly shutted off the engine because I want to be sure that the instrument sensor is over estimating temp and not the engine management receiving an under estimated value (the instrument never read near the red line however).
I buy a new instrument temp sensor and then it will be sorted !
Stalje said:
Looks like we made a huge progress!
I tested every wire continuity and it is all perfect.
I decided to redo a real test with a running engine.
Voltages were as expected on the fan controller module (12v when cold, then dropping when reaching target temp).
I plugged the OBD reader in this situation and saw that the instrument binnacle told be a different rear from the OBD. I took the risk to continue and trust the obd value then at 99° fans finally ran... I immediatly shutted off the engine because I want to be sure that the instrument sensor is over estimating temp and not the engine management receiving an under estimated value (the instrument never read near the red line however).
I buy a new instrument temp sensor and then it will be sorted !
I tested every wire continuity and it is all perfect.
I decided to redo a real test with a running engine.
Voltages were as expected on the fan controller module (12v when cold, then dropping when reaching target temp).
I plugged the OBD reader in this situation and saw that the instrument binnacle told be a different rear from the OBD. I took the risk to continue and trust the obd value then at 99° fans finally ran... I immediatly shutted off the engine because I want to be sure that the instrument sensor is over estimating temp and not the engine management receiving an under estimated value (the instrument never read near the red line however).
I buy a new instrument temp sensor and then it will be sorted !
I'm working on a similar problem with my 1998 Db7. Wiring diagrams are not very good.
The signal that controls the Fans comes from the POWERTRAIN CONTROL MODULE. It then goes thru a series/Parallel Control Module to the fans. If your running the fans with a OBD bypass signal , keep in mind when you do a live test the BONNETT must be closed or the fans won't run. (There is a interlock switch under the left engine panel. )
If your driving in traffic and your Temp starts to climb you can force the fans to come on by putting on the A/C anytime the A/C compressor comes on the fans come on.
Good luck
Mr. Hoyt
The signal that controls the Fans comes from the POWERTRAIN CONTROL MODULE. It then goes thru a series/Parallel Control Module to the fans. If your running the fans with a OBD bypass signal , keep in mind when you do a live test the BONNETT must be closed or the fans won't run. (There is a interlock switch under the left engine panel. )
If your driving in traffic and your Temp starts to climb you can force the fans to come on by putting on the A/C anytime the A/C compressor comes on the fans come on.
Good luck
Mr. Hoyt
Here I am two years after... I forgot to give a feedback about my issue.
To be honest, I was halft part of the problem. I had an issue with the instrument temperature sensor that i replaced... While I changed the sensor for the ECU as well.
It seems that the ECU one was misreading, therefore it didn't matched the reading on the cluster. And since this value was incorrect, the additionnal effect that the engine temp. climbed faster when sollicitated.
I finaly bought a new IC sensor from Aston to be 100% sure it worked as it should.
I was quite puzzled by the reading on the cluster at the beginning but you have to have in mind that this engine runs HOT ! 100-105 is the target temp, far from the 90-95 range we are used to on older cars.
I also had an issue with the fuse for the secondary fan (which should run when the temp is over 100°c) sometimes blowing with the 25amp stock fuse . I finaly tested with a 30 amp and never encountered this issue since. I imagine that the fan motor is not as free as it was when "new".
I now have a full aluminium radiator with a 90°c thermostat, the stock ECU temp sensor and a new Aston Martin IC temp sensor. I may swap for a stock thermostat since everything seem to be sorted.
Damn this was nerve-racking to do all these tests and fear for a head gasket issue... But hope It will help.
To be honest, I was halft part of the problem. I had an issue with the instrument temperature sensor that i replaced... While I changed the sensor for the ECU as well.
It seems that the ECU one was misreading, therefore it didn't matched the reading on the cluster. And since this value was incorrect, the additionnal effect that the engine temp. climbed faster when sollicitated.
I finaly bought a new IC sensor from Aston to be 100% sure it worked as it should.
I was quite puzzled by the reading on the cluster at the beginning but you have to have in mind that this engine runs HOT ! 100-105 is the target temp, far from the 90-95 range we are used to on older cars.
I also had an issue with the fuse for the secondary fan (which should run when the temp is over 100°c) sometimes blowing with the 25amp stock fuse . I finaly tested with a 30 amp and never encountered this issue since. I imagine that the fan motor is not as free as it was when "new".
I now have a full aluminium radiator with a 90°c thermostat, the stock ECU temp sensor and a new Aston Martin IC temp sensor. I may swap for a stock thermostat since everything seem to be sorted.
Damn this was nerve-racking to do all these tests and fear for a head gasket issue... But hope It will help.
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