TD5 battery connected wrong way round

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Declan Ashley

Member
Posts
13
Location
Northampton
Hi,
My mums 1999 TD5 discovery's battery died tonight whilst she was at work, so I went to try and get it started. I decided to swap over the dead battery with a spare I have, so I took off the dead battery and as I touched up the good battery, the horn sounded, bearing in mind it's 11 at night in mums works car park, so I put the dead battery back on. Then the key fob wouldn't do anything, it wouldn't lock or unlock the doors, and when I turned the ignition on the dash beeped and a B with a line through it flashed on the odometer, and the engine wouldn't turn over. I should have probably tried to jump start it first, but my jump leads are rubbish so I didn't think it would work. Does anyone know what the beeping or flashing B with the line through it means? I've attached a picture of what I mean. Any suggestions on how to get it running?
Thanks
 

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Pulled from elsewhere so I can't vouch for it but.....

''As this old thread was resurrected i'll tell you all the ''secret'' of that crossed B... it's bad news even if it's not mentioned in any document, it's about a missing signal in the data bus between the BCU and IDM(part of the interior fusebox), i've seen it on a few D2s and my rough statistic is:
- 30% IDM fault mostly caused by water ingress in the interior fusebox
- 69% BCU internal fault, also can be caused by water ingress or voltage spikes
- 1% datalink interruption

when you see it be prepared with a replacement fusebox and BCU within reach cos it has various symptoms and can lead to completely immobilised vehicle too and it's almost impossible to rule out which one is at fault without replaceing it if no obvious signs of water ingress or corrosion, in this case the best is to start with the fusebox cos it's plug and play and no programming needed unlike the BCU where a dedicated D2 tester is compulsory''

All that electrickery is a bit beyond me but when I was trying to start the Doris' bug with a dodgy battery the alarm went off a couple of times. It was fine after jumping it though
 
Thanks for the quick replies, I agree that the battery could be knackered, as it has gone flat quickly before. is there anyway to prevent the horn sounding if I connect the good battery back up?
 
Remove horn relay(R13) before you swap batteries cos the alarm sounder is not so loud then when the good battery is on unlock immediately with the fob,... if thist doesnt work it means it's that ''crossed B" problem quoted above and the battery failure was coincidental...then search "crossed B" with the forum's facility cos it's covered
 
Went again to try and start the discovery, I thought I'd try and put the good battery back on. However as it was dark and cold last night, it seems I stupidly must have connected my spare battery the wrong way round, thankfully the loud horn meant it wasn't connected for long. So I checked fuses under the bonnet and under the steering column, two were blown so I replaced both and all seemed to be normal again. I then connected it to another car using jump leads, and managed to start it, then the battery light was on, and gradually all the electrics stopped working (indicators, lights, etc). I have managed to get the car home and have have jump started it again, currently the Windows, radio, wipers, blowers and I think rev counter and speedo don't work. All the fuses seem fine. So is there anything I can do to try and get the alternator working or will it need replacing? And any ideas on what's wrong with the interior electrics?
Thanks
 
Would be good to know which fuses were blown, also check maxi fuse FL1 in engine bay fusebox, undo one side and check continuity, also double check fuses F24, F27 interior fusebox, not just eyeball them replace with new or check continuity... if all these are good start it somehow and check voltage on the battery with engine running, if you dont get around 14V the alternator is gone, if the alternator is good too make that search for "crossed B"
 
The fuses that were blown were F13 and F4, replaced both and have also replaced F24 and F27, which made no difference. Haven't checked FL1 or battery voltage with engine running as I don't have a multimeter, will get one tomorrow and test both.
Thanks
 
Thats strange as when I replaced the fuses the car then went back to normal, as in the key fob worked again, the B with the cross didnt appear and the car started. Any idea on what is causing the windows, wipers, blowers and radio to not work?
 
While you're checking fuses, it's worth trying them with a meter and measuring resistance. I had some puzzling electrical problems a while ago and it turned out that a fuse had suddenly developed a resistance of around 80 ohms. So it looked OK in terms of continuity but yielded symptoms when it was actually expected to do something.
Otherwise I can't comment on the D2's peculiarities because I've never had one.
 
Declan Ashley said:
Thats strange as when I replaced the fuses the car then went back to normal, as in the key fob worked again, the B with the cross didnt appear and the car started. Any idea on what is causing the windows, wipers, blowers and radio to not work?
Click to expand...
It's strange because i've had a mental hiccup and spoke about interior fuses, yes F13 is important cos it's feed for IDM, BCU and ECU so that could have caused that the question is why was it blown?

about windows, wipers radio, check fusilble link FL7 and if it's good swap relays R7 with R8 and see if it goes, if yes put new instead of what was 7
 
Just had a look, FL7 looks fine, but can't be sure without a meter, this discovery doesn't have an R8 relay, as it doesn't have a heated front windscreen, can I swap R7 with any others?
 
The glow plug warning lamp has nothing ti do with the plugs or relay, it's managed exclusively by the engine ECU...let's wait untill FL7 is ruled out for good
 
Just got a multimeter and have been doing some testing, battery voltage with engine off is around 12.5v, with engine running it is around 12.1v. It seems FL1 has blown, no continuity. FL7 seems fine, continuity and low resistance and R7 also seems fine. Could FL1 cause the alternator to not work?
 
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