P38A She’s Dead, Jim

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awkwardbob

awkwardbob

Well-Known Member
Posts
578
Location
Glasgow
So I guess this is a big welcome to p38 ownership...

just when I thought I’d everything sorted, she wasn’t marking her territory with oil leaking everywhere, I went to check fluid levels before heading to work this morning and ‘boom’ nothing.

no central locking, no signs of life at all.
I’m assuming some kind of electrical catastrophe but I don’t really understand it.

I last drove her around 10 days ago, the battery registering a healthy 12.5V and she’s been sitting since.

The battery is 2 months old and the central locking RF thingy is disconnected to prevent battery drain.

I didn’t have time to get a meter across the battery but is this the most likely culprit ? -or is there something more sinister which could cause a complete electrical shutdown ?

hoping it’s something straightforward...

thanks again for your help

Bob
 
awkwardbob said:
So I guess this is a big welcome to p38 ownership...

just when I thought I’d everything sorted, she wasn’t marking her territory with oil leaking everywhere, I went to check fluid levels before heading to work this morning and ‘boom’ nothing.

no central locking, no signs of life at all.
I’m assuming some kind of electrical catastrophe but I don’t really understand it.

I last drove her around 10 days ago, the battery registering a healthy 12.5V and she’s been sitting since.

The battery is 2 months old and the central locking RF thingy is disconnected to prevent battery drain.

I didn’t have time to get a meter across the battery but is this the most likely culprit ? -or is there something more sinister which could cause a complete electrical shutdown ?

hoping it’s something straightforward...

thanks again for your help

Bob
Click to expand...
12.5volts is not that healthy and 10 days sitting may well have been enough to flatten it. A failed diode in the alternator will flatten the battery.
What size battery is it? Petrol or diesel?
 
Give the battery a good charge over night them leave for an hour and test the voltage you should have about 12.8v.
 
Datatek said:
12.5volts is not that healthy and 10 days sitting may well have been enough to flatten it. A failed diode in the alternator will flatten the battery.
What size battery is it? Petrol or diesel?
Click to expand...

Sorry, it’s a 4.6l Gems.

The battery is a Yuasa, will need to check the size but it’s reasonably chunky -the Bosch that was in before was woefully under-specced.

Would a duff diode even drain the battery at rest ?

will take some readings in the morning which may help diagnose.

thanks again

Bob
 
They don’t like standing without a run for long. Can eat a battery overnight in some circumstances, can fail at any time without warning.
Is it under warranty? Usually get couple of years one with a battery.
I’m guessing you don’t use a trickle charger? If it’s suitable for you a c-tek is only about a fiver don’t see people complain about them seem to work well.
 
In answer to your question, yes, a duff diode will flatten the battery whilst standing.

A couple of questions. Is your 12.5V at rest or running? 12.6V is fully charged at rest, once the surface charge is dissipated. If it is 12.5 running, the alternator is dead.

If it is 12.5 sitting, what is (was) it running? Depending on the alternator it should be between 13.5 ish to 14.5 ish. If not, once again, alternator.

As for a blown diode in the rectifier, you can sometimes detect it by looking at the dash lights with the engine running. If they seem to pulse, then your rectifier is toast.

Rectifiers and voltage regulators are cheap and an easy DIY to install, as long as you have a big soldering iron.
 
Marshall8hp said:
In answer to your question, yes, a duff diode will flatten the battery whilst standing.

A couple of questions. Is your 12.5V at rest or running? 12.6V is fully charged at rest, once the surface charge is dissipated. If it is 12.5 running, the alternator is dead.

If it is 12.5 sitting, what is (was) it running? Depending on the alternator it should be between 13.5 ish to 14.5 ish. If not, once again, alternator.

As for a blown diode in the rectifier, you can sometimes detect it by looking at the dash lights with the engine running. If they seem to pulse, then your rectifier is toast.

Rectifiers and voltage regulators are cheap and an easy DIY to install, as long as you have a big soldering iron.
Click to expand...

yeah, 12.5V at rest 13.8V I think when running.

Im sure I’ve left her longer than that without a run -and I didn’t leave the headlights on !

will check the battery in the morning and go
From there.

Did have a slightly weird dash light thing where the RHS of the odometer / info screen wouldn’t light up initially but then would spring into life. No flicker though.
 
13.8 volts is not enough to charge a modern battery, needs to be around 14.7 volts. If your Yuasa battery is an AGM battery, IMO they are not suitable for vehicles except really modern stuff.
Your battery will have been running under charged which shortens the life.
A failed diode in the alternator can flatten the battery.
 
The P38 is an E-Motor disguised with an IC engine. ;)
They eat Batteries. Fix all the underlying faults (BeCM insomnia etc.) and they are not so bad.
The RF unit for the FOB receiver is a common source of "woke", the LR receiver that fixes the LR problem is now >£300.
MartyUK on here sells a filter unit for c.£80 notes and it fixes the issue.
 
Im just wondering :rolleyes: if 13.8 volts is a cleaner supply of power to protect the old circuitry in these beasty's ,When the volts go up is that when owners start having ecu probs ect :eek:......its just a thought ,is 14.7 volts as stable as 13.8v ....Iv had mine 11 years :p ...and .....cant say any more cause you,s all know what will happen ,,,but im on my 4th battery its an Oldham, lead acid ,been good now for about 4 to 5 years....all the rest lasted about 2 years..:confused:
 
dubbleRR said:
Im just wondering :rolleyes: if 13.8 volts is a cleaner supply of power to protect the old circuitry in these beasty's ,When the volts go up is that when owners start having ecu probs ect :eek:......its just a thought ,is 14.7 volts as stable as 13.8v ....Iv had mine 11 years :p ...and .....cant say any more cause you,s all know what will happen ,,,but im on my 4th battery its an Oldham, lead acid ,been good now for about 4 to 5 years....all the rest lasted about 2 years..:confused:
Click to expand...
All the ECU's contain voltage regulators because the logic runs on 5 volts. 14.7/14.8 volts will do no harm, 13.8 is no cleaner than 14.7, there is considerable ripple on an alternator output which is absorbed by the battery. Lack of full charge shortens battery life.
My first MF31-1000 lasted 8 years and was destroyed when the alternator failed.
 
Thanks chaps,

I’m just going to check battery and so on. I’m just puzzled as this battery is only 2 months old.

the RF FOB receiver is disconnected to stop theBECM waking.

I had to buy the battery in a hurry as she died outside Halfords and it was the only big one they had with the terminals the ‘right’ way round. The buggers never emailed me the receipt though…

back shorty with more details
 
Ok, so the battery is reading a sorry 0V DC.

it’s a Yuasa HSB334: 100AH, 830 CCA

It claims to have a 5-year warranty.

the alternator is a, presumably OEM, Magnetti Marelli affair.

What would the advice be ?

recharge battery ?
Claim on battery warranty ?
Buy a more suitable battery ?

change alternator for one more suited to modern batteries ?

Buy an expensive bottle of Rum and drown the sorrows ?

any help/advice is most welcome

Bob
 
awkwardbob said:
Ok, so the battery is reading a sorry 0V DC.

it’s a Yuasa HSB334: 100AH, 830 CCA

It claims to have a 5-year warranty.

the alternator is a, presumably OEM, Magnetti Marelli affair.

What would the advice be ?

recharge battery ?
Claim on battery warranty ?
Buy a more suitable battery ?

change alternator for one more suited to modern batteries ?

Buy an expensive bottle of Rum and drown the sorrows ?

any help/advice is most welcome

Bob
Click to expand...
Buy me the rum and then after drinking it I can advise better:rolleyes::rolleyes:
 
If you charge the battery ,it will be hard if its that low ,might need a smart charger and it might not see it ,,my one needs 2 volts to start with so i use recover pulse mode :( but you still need to find the cause of the drain ;),when you reconnect the battery if it gives a bit of a big spark then something's pulling big power ,,try disconnecting the alternator see if its less ,,,, then hit the rum :rolleyes: :D:D:D:D..
 
dubbleRR said:
If you charge the battery ,it will be hard if its that low ,might need a smart charger and it might not see it ,,my one needs 2 volts to start with so i use recover pulse mode :( but you still need to find the cause of the drain ;),when you reconnect the battery if it gives a bit of a big spark then something's pulling big power ,,try disconnecting the alternator see if its less ,,,, then hit the rum :rolleyes: :D:D:D:D..
Click to expand...
If a charger doesn't see the battery, you can connect to another car battery, put the charger on. After a few mins, you should be able to disconnect the donor battery, but remember to charge it afterwards as well
 
awkwardbob said:
Ok, so the battery is reading a sorry 0V DC.

it’s a Yuasa HSB334: 100AH, 830 CCA

It claims to have a 5-year warranty.

the alternator is a, presumably OEM, Magnetti Marelli affair.

What would the advice be ?

recharge battery ?
Claim on battery warranty ?
Buy a more suitable battery ?

change alternator for one more suited to modern batteries ?

Buy an expensive bottle of Rum and drown the sorrows ?

any help/advice is most welcome

Bob
Click to expand...

If the interference is strong then disconnecting the receiver is not enough. Is there a wireless weather station nearby? That's what was waking mine.
 
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