- My model of MX-5 is: 2007 NC Sport 2.0
- I’m based near: West Wales
- I’m looking for technical help or recommendations on: Battery drain
Apologies - topic was created before I had a chance to explain the issue in depth!
I have an issue with my MX5 NC Sport 2.0L with the battery becoming completely discharged after 4/5 days if the vehicle is not used. The battery is new and 100% charged. The vehicle has previously suffered water ingress via both the rear drains and the front scuttle panel and I believed that the source of the battery drain was the Bose head unit / power amp. I have taken it to an auto electrician to verify the cause before embarking on upgrading the infotainment system and they have called to say that the source of the power drain is, in fact, the instrument cluster. They have said that to investigate precisely what within the instrument cluster is causing the drain would be prohibitively time consuming and costly and have suggested replacing the instrument cluster with a used unit.
Is a failure of the instrument cluster a known phenomenon? All instruments, lights, warning lights, gauges are working fine.
The garage is recommending replacing the instrument with a used unit from an identical vehicle (which obviously would have no guarantee) but have indicated that the data from the original unit would need to be downloaded and coded onto the replacement to preserve mileage, etc.
The overall cost, including the purchase of the second hand instrument cluster, specialist coding of the replacement and swapping out is estimated in the region of £500/600, and whilst the garage is confident that this will solve the problem they cannot offer a complete guarantee.
I would greatly welcome the thoughts and observations of the community (apologies - whilst I am generally ok with mechanics, electrics are a “dark art” to me!!!)
Cheers! Richard
A simple check, did you check or have you had your battery checked? These battery problems always crop up in winter, a battery not holding a charge may tell you on the charger it’s 100% charged when not. I’ve had two batteries one more recently where it says fully charged but basically they needed replacing.
Mick, he said that the battery is new and 100% charged.
Ahh, missed the new bit.
4/5 days is a bit quick, what is the actual drain in amps? Does the drain disappear if the “room” fuse (fuse 5) in the engine bay fuse box? or the meter fuse (fuse 3) in the kick panel fuse box are removed? Have you made sure the boot light goes out when the boot is closed? (use a smart phone set to video in the boot when the lid is shut).
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Being a sport - I am guessing it has the BOSE stereo ?
I have seen on a few forums where the Bose amp can drain the battery quite quickly when it is starting to fail.
Try pulling the 20amp fuse that feeds the amp.
You won’t have stereo sound whilst the fuse is out but it will tell you if the amp is the drain on the battery.
Thanks - it does indeed have the Bose system with the separate amp. This was one of my prime suspect for the source of the battery drain having read several articles like you and recognising that, given its location, it would have been vulnerable when the rear drains became blocked. Auto electrician, however, is adamant that having checked all components, the instrument cluster is the culprit. Replacement used instrument cluster now being ordered which will then be sent to be “cloned” with the data from the original - fingers firmly crossed!
I said in another thread, check the alternator. Alternator failure (diodes) can lead it to drain a battery, without warning lights.
I have the same model and am suffering from the exact same issue.
Garage have previous told me that there is no obvious problem.
Thanks for all the advice chaps. Given me a few things to check.
I feel your pain - ended up replacing both the Bose head unit and the instrument cluster and, at least thus far after a couple of months, the problems seem to have been resolved.
Good luck!
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I am now experiencing a similar problem. Coinciding with driver side water ingress into footwell through the windshield scuttle. My theory is it’s also instrument cluster draining the battery. Yay.
Yaaargh, it’s contagious!
Same model and I appear to have acquired a current vampire too.
Battery was flat on the really cold day we had last week and the car hadn’t run for a few days. The battery was at least 5 years old so rather then faff about I had next day delivery on a new one.
All was fine for a few days then car not used for three days and when I tried to start today, flat as a pancake. No water ingress, connections right, scuttle grommets well sealed, aftermarket radio, no Bose amp. The only thing I’ve done electrically recently was add led lighting in the boot so I double checked that and all ok; it goes off when the lid is shut.
I’d already recharged the old battery and put it in and I’m just about to go out in the dark and the rain too get a quiescent current reading after the car’s been sitting for an hour and will start pulling fuses tomorrow if there’s a break in the clouds.
Update :
130mA after 90 minutes, so just over 3Ah per day
That doesn’t sound excessive to me and I think I’ve seen that figure as normal elsewhere. Could be a tricky one🤔
Check the voltage at rest should be 12.6, then check with the engine running, it should be over 14.2. Also check the voltage the following day to see if it falling
That’s about a 100mA too many!
Something is still switched on.
Unlikely, but cruise control left on was a problem with early NDs, and so the console computer was active. Could it be the case with late NCs?
Thanks Richard.
I thought I’d seen the figure of 130mA somewhere as normal. No cruise control, so it’s not that. I’ll start pulling fuses tomorrow.
Hi Andy, I’m in the same boat as you. Investigation begins… Let us know how you get on
My situation: dash cam (disconnected since problems began), BOSE amp, aftermarket stereo. Water ingress on driver side - sealed up over the weekend. Battery only 1.5 years old and tested working fine according to kwik fit alongside the alternator.
Auto electrician booked 8th January. DIY diagnostics ongoing in the meantime. Need to get myself a better multimeter…
Some things to consider.
Have the “Permanent” Live and “Ignition Switched Live” to the head-unit been inadvertently swapped over?
Is the Bose amplifier on all the time? (could be so if that swap has happened.)
Bose amp was faulty and repaired 2 years ago. Headunit was installed 3 years ago. Haven’t changed the wiring recently since draining problems started (about a month ago)… I will be pulling fuses and prodding at things with a multimeter
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Apologies for hijacking this thread a bit but it appears that the OP’s problem has been solved with a replacement instrument panel.
Checking today using the old battery which is now fully charged I’m getting 12.6V at the battery engine off, 14.6V with engine running so all OK there.
Current draw from the battery is now giving me 300-400mA immediately after connection dropping to 130mA after a few seconds then down to 15mA after about a minute and a half.
By pulling the “room” fuse I could see the 15mA is drawn from the cabin; with the fuse out the draw direct from the battery is zero . . .
. . . which puts me no further forward really and I’m thinking probably the 130mA I was seeing last night was because I wasn’t standing out in the rain long enough measuring it.
So, I’ve got a spare charged battery ready for a quick swap if need be and I’ll monitor the situation, hoping this was just a temporary thing. If it reoccurs I’ll put together some sort of logging arrangement to monitor the battery to try and pin it down.
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