Battery, immobiliser, fans and speedo woes. Any ideas?
Discussion
Since getting the car back from a service a few months ago I noticed the battery would drain after a few days. Convinced the battery was knackered, I extracted it from the car and took it back to Halfords (under warranty), only to be told it was fine.
It reads 13.5v when engine is running - is that about right? The other day I just about managed to start it when leaving work, 30 min drive to school pick up, only for it to not have enough juice to restart the engine again. That was pretty embarrassing and didn’t do the TVR reputation much good.
The other day I noticed I no longer need to disarm the immobiliser. Any ideas why that might be? Obviously, if it’s continually trying to activate when the car’s turned off, this might explain the battery drain.
In the past couple of weeks the speedo is going a bit wild. The controller has never been changed in the 13 years of ownership, so perhaps coincidence?
Finally, after getting stuck in traffic just now, the engine was about to overheat and realised the fans weren’t kicking in. The ECU software showed them active.
Whilst in the software, the fault code Battery Log was lit up.
Any ideas where to start?
Cheers!
It reads 13.5v when engine is running - is that about right? The other day I just about managed to start it when leaving work, 30 min drive to school pick up, only for it to not have enough juice to restart the engine again. That was pretty embarrassing and didn’t do the TVR reputation much good.
The other day I noticed I no longer need to disarm the immobiliser. Any ideas why that might be? Obviously, if it’s continually trying to activate when the car’s turned off, this might explain the battery drain.
In the past couple of weeks the speedo is going a bit wild. The controller has never been changed in the 13 years of ownership, so perhaps coincidence?
Finally, after getting stuck in traffic just now, the engine was about to overheat and realised the fans weren’t kicking in. The ECU software showed them active.
Whilst in the software, the fault code Battery Log was lit up.
Any ideas where to start?
Cheers!
- I would say 13.5V might be a little on the low side, more like a good battery with no alternator input - I normally see 14.2 once the engine's running. Worth checking the alternator and connectors?
- Don't know about immobiliser, though if the battery's constantly going flat, it probably doesn't help it not having a consistent power source?
- Wild speedo - worth checking the speed sensor and speed sensor wiring (picks up from the left hand driveshaft bolts IIRC?). Wiring runs up into the boot and plugs into a connector accessible under the carpet on top of the fuel tank. Clean up everything under the car, and check the connector inside. Mine went wild last year, and I found the wiring to the connector was corroded. Replaced the connector - all sorted.
- Fans not coming on. Fuses, relays, but first point to check would be the fan connectors. They're not weatherproof, and a bit exposed to the elements down the front of the car. Clean up might sort it out - did for me when I first got the car.
Good Luck!
- Don't know about immobiliser, though if the battery's constantly going flat, it probably doesn't help it not having a consistent power source?
- Wild speedo - worth checking the speed sensor and speed sensor wiring (picks up from the left hand driveshaft bolts IIRC?). Wiring runs up into the boot and plugs into a connector accessible under the carpet on top of the fuel tank. Clean up everything under the car, and check the connector inside. Mine went wild last year, and I found the wiring to the connector was corroded. Replaced the connector - all sorted.
- Fans not coming on. Fuses, relays, but first point to check would be the fan connectors. They're not weatherproof, and a bit exposed to the elements down the front of the car. Clean up might sort it out - did for me when I first got the car.
Good Luck!
Thanks for all that Pete. Really useful info.
S6boy - it’s about 12.2v from memory. But drops each days. 12.6 is charged, 12.2 is something like half. I’ve been charging it each night because been wanting to use it each day whilst the weather’s so good. What I need to do is disconnect that battery and see how quickly it drains overnight, and also check for parasitic drain. It’s just such a pain getting to the battery!
I’m wondering whether I might have a bad earth. Could that be the cause of a few of these issues I wonder? Perhaps the mechanic didn’t tighten something properly as it’s only been happening since getting the car back from the garage (the battery issue that is).
S6boy - it’s about 12.2v from memory. But drops each days. 12.6 is charged, 12.2 is something like half. I’ve been charging it each night because been wanting to use it each day whilst the weather’s so good. What I need to do is disconnect that battery and see how quickly it drains overnight, and also check for parasitic drain. It’s just such a pain getting to the battery!
I’m wondering whether I might have a bad earth. Could that be the cause of a few of these issues I wonder? Perhaps the mechanic didn’t tighten something properly as it’s only been happening since getting the car back from the garage (the battery issue that is).
There is an earth point on the left-hand side behind the battery; it connects the battery to the frame and the control units located in the cab. This earth point is bolted from both sides (footwell and battery compartment). It is therefore essential to counter it, otherwise you will loosen the screw connection on one side when trying to screw it on the other side. However, this is not a typical point for screwing during servicing.
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