Discussion
A topic that has been covered before but I'm stumped. On my car when the engine gets hot the offside fan comes on at about 97 degrees - the nearside one never comes on. I'm investigating what is wrong as I assumed there must be a problem with the nearside fan or the power supply to it. So I've removed the air box and disconnected the water temperature sensor by port number 5. On my car the engine then actually has be running for the fans to actuate - not just with the ignition on and the immobiliser de-activated. When I do this only the near side fan comes on not both fans. So only the offside comes on with high water temperature and only the nearside with a cold engine and the temperature sensor disconnected. What's the cause of those symptoms....
The good news is you have a cooling fan, but it doesn't come on until nearly 100 meaning it's the secondary fan presumably.
You've proved electrical connectivity to both fans and the fans themselves - also good.
I know my fans go off with the engine but never tried turning the immobiliser on again just with the ignition, but would think this is normal?
If so all it means is the primary fan is not being switched and as you've proven it at the sensor I'm guessing it could be an ECU issue - not so good.
Sorry not much help and it's been a long day so hope I've got the right end of the stick.
You've proved electrical connectivity to both fans and the fans themselves - also good.
I know my fans go off with the engine but never tried turning the immobiliser on again just with the ignition, but would think this is normal?
If so all it means is the primary fan is not being switched and as you've proven it at the sensor I'm guessing it could be an ECU issue - not so good.
Sorry not much help and it's been a long day so hope I've got the right end of the stick.
Hi John - I'm guessing that it might be some sort of ECU/software issue but I'm interested if someone has another take on the problem. I find it hard to believe that such an fault could develop in the ECU - it would have to be some sort of inverse logic issue which shouldn't just appear. Anyone got other ideas or have seen the issue?
The relays do fail even though they may operate the contacts develop a high resistance and the relevant fan does not come on. Also the connectors can corrode as they have no waterproof shroud on them. There is also a fuse for each fan and these should be checked. If you have the diagnostic software you can see if the ECU is switching the fans on.
I think what bobs saying is even with the temperature sender unplugged only a single fan comes on, where as at 97 both should be running simultaneously.
I would look at the wiring diagram posted by Rhyspw and measure the voltage at the relays and at the fan connectors when they should be running.
Have you definitely disconnected the correct sensor and I'm presuming they were previously working.
I would look at the wiring diagram posted by Rhyspw and measure the voltage at the relays and at the fan connectors when they should be running.
Have you definitely disconnected the correct sensor and I'm presuming they were previously working.
Thanks to everyone for their input. Taking some of the points made. The offside fan has worked consistently ever since I've had the car - bought earlier in the year and operates at around 97 degrees. I guess it's possible that TVR wired it wrong so it's the one that should come on at the lower temperature and the 'gauge' is reading high. That would however mean two errors simultaneously which I think is unlikely and wouldn't explain why it stops working when the fan temperature sensor is disconnected. As far as I'm aware the nearside fan has never worked and sprang into life for the first time when the previously mentioned sensor was disconnected. I guess it's possible there could still be some continuity issues but it seems very unlikely. The sensor I disconnected is definitely the correct one from all the various forum posts and Graham Varley's site. I'll have another look at the wiring diagrams but those recently posted and those here: http://www.thetvrsite.com/cerbera/wiring-diagrams don't show the logic regarding how things work just wires and connectors. Maybe I'll have a look at getting some diagnostic software up and running but I'm a mechanical guy not an electronics/computer engineer. Any advice on the latter - what to download, how to connect the PC to the car and how to operate the software would be appreciated. Failing that I'll leave it to the 'experts'.
m4tti said:
Sounds daft but with the sensor unplugged have you wiggled the fan connectors. The oxidisation of the spade terminals in those connectors can cause odd intermittent problems. I clean them every year.
Thanks Matt - I'm going to go through all the connections/fuses/relays etc just in case there is a problem there as I know both fans actually work.BobE said:
m4tti said:
Sounds daft but with the sensor unplugged have you wiggled the fan connectors. The oxidisation of the spade terminals in those connectors can cause odd intermittent problems. I clean them every year.
Thanks Matt - I'm going to go through all the connections/fuses/relays etc just in case there is a problem there as I know both fans actually work.Hopefully everything will now work as intended. I'll then move onto the starter motor issue I have and maybe replace the battery as well. It seems there is always an ongoing project with a specialist British sports car - I've had years of 'fun' over the last few decades with Triumph, Marcos and Nobles and now TVR.
I bet you its just bad fan connectors. Very common fault as they're largely unprotected from the weather and for some bizarre reason aren't wet environment type connectors.
Exact same issue with mine years ago so I replaced both connectors and it fixed it. I also sprayed plenty of silicon spray all over them as well with a view to protecting them from the weather a bit better. Been fine ever since.
Exact same issue with mine years ago so I replaced both connectors and it fixed it. I also sprayed plenty of silicon spray all over them as well with a view to protecting them from the weather a bit better. Been fine ever since.
Just to conclude the topic - everything is now sorted. Two new relays and two new connectors fitted adjacent to the fans. For the latter I couldn't find any sealed versions capable of taking 30amps - most were only 15 to 19amps and with a 30amp fuse I didn't fancy the weakest link being the connectors if a short occurred in a fan motor. I then tried replacing the connectors like for like as mine had very badly corroded terminals and the corrosion had spread up the wiring loom copper conductors under the plastic sheathing but I couldn't crimp the new ones on without a major disturbance of the wiring harness. In the end I used domestic 30amp connector blocks with all the terminals and screws heavily coated in dielectric grease after assembly and then used two lengths of cable protector conduit over them as drip and splash guards. End of problem.
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