P38A Battery replacement and draining issues

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awkwardbob

awkwardbob

Well-Known Member
Posts
590
Location
Glasgow
Hey there,

I’ve a newly-acquired 1998 4.6 autobiography and I seem to be getting my hands dirty from the off !

currently have a Bosch 069 series battery which seemed to be ok but suddenly is draining terribly.

the battery is currently delivering g a mere 1.8V and I suspect has had it.

I’d also like to get to the bottom of the current drain too and it seems probable that it could be the key fob RF receiver which is stock original.

so I wondered whether anyone had any advice on batteries ?

I can replace like for like with Bosch or I can go for a bigger ‘commercial’ Lion battery for about the same (c£150). What would you recommend ? The RR is likely only going to be used occasionally rather than daily.

with the RF unit, I’ve heard eye-watering prices quoted and 2nd gen (blue dot?) and 3rd gen (green dot ?) parts spoken about.
Can I just disconnect the current unit to test if that’s the issue ? what do I ‘lose’ by disconnecting ? Is it just remote locking ? Or would permanently removing it cause other issues ?

Thanks from Autumnal Glasgow
 
I bought that Hankook battery last year, and it's good.

For the Fob Receiver, first step is to disconnect the antenna wire. The fob will work when it's near the rear window, and the BECM wake-up should stop unless your interference is really strong & nearby. Best long term solution is @martyuk 's Fob Filter which works with all receiver versions.
 
awkwardbob said:
Thanks folks !
Disconnecting seems like a sensible first step. Is it the bigger or smaller connector ?
Click to expand...

It won't stop strong signals. Best use Brian's remote jog switch or Marty's filter. Otherwise you'll get buying new lock actuators too.

Your alternator might only kick out 13.8V which will kill calcium batteries. I like the Platinum 642X.
 
Wouldn't touch a Lion brand with a barge pole.
Used one a few years ago on my RRC & had two replacements in the warranty period, fine for around 9 months & as soon as the weather got cold that was it.
When I took the 2nd one back the chap behind the counter cheerfully told me they reckoned to get around 1/3 of them back in the warranty period.
I'm trade & I think he assumed it was for a customer's car.
They MAY have improved since but I won't risk it.
 
Last edited:
Thanks folks,

Would certainly plump for the fob filter but it seems to be out of stock :(

Maybe a disconnect in the short term and a new battery to tide me over until the filter is available again.

I'll maybe drop Marty a PM and see if its likely to be back in anytime soon.

Cheers

Bob
 
Bob, I wd check the alternator/ VR, as noted above - you may have a drain, but equally the alternator/ VR may simply not be working. The VR can be had for about £20 if you find the right one for your alternator. - mobiletron ones seem to have a 14.7V set point (future proofed) other makes seem a bit more hit and miss, whereas original spec was 13.8V.
I'm not sure I ever had a drain, but I disconnected my RF receiver when i first got it, and have never bothered reconnecting it. It depends what you're happy with, i don't mind only being able to use the remote a few metres from the car, so the filter seemed an unnecessary expense. The receiver is only responding to 433MHz, rather than wifi etc
 
Thanks Rob,

I have seen an intermittent alternator warning light but I put it down to electrical
Gremlins.

I thought it odd that my battery drained completely flat in 2 days when parked.

having had it in trickle charge for 24 hours it now seems healthy again so perhaps it’s a combination of the two things.

As the car is only for occasional usage, I like you, are probably happy to just disconnect the aerial if that helps fix the problem.

i wonder whether a chunkier battery is a good purchase in any case as a back up.

I’ll check the voltage with the engine running to see what’s coming out of the alternator once I bolt everything back together.

mid the voltage
Regulator obvious and easy to spot / replace ?

thanks again

bob
 
Yes, the VR is an easy fix (black plastic cover on the back of the alternator), but there is a random bracket off the GEMS fuel rail that might make it tricky to remove the cover in situ. I whizzed it off with a Dremel, as it does naff all. I say easy fix... Magneti Marelli ( if you have the original alternator) used some ridiculously small screws, and you'll need a little mechanics mirror to find /remove them. On mine that was two for the black plastic cover, and three on the VR itself - not including having to remove the cabling off the terminal posts.

Very occasionally I get an intermittent Alternator light - infrequent is ok IMHO, but continuous obv not. P38 will suck power from the battery v quickly if the alternator is not working properly.

Larger battery may be useful, but equally may just mask a passive drain issue, and take even longer to recharge. Disconnection is a good idea if you leave it for a long period - if the car is healthy (door microswitches) and you have your EKA (for back up). Unlock the doors, disconnect the battery, lock the doors manually, DON't press the fob buttons if you can help it, prior to reconnection of the car battery.
 
Last edited:
Hey Rob,

only marking I can see in
The alternator is B56 or B66,

the black plastic cover has the Magneti Marelli logo on it.

battery voltage after charging is 12.24V

voltage at terminals with engine running is: 13.79V

does this seem ok ? Or I be concerned ?

thanks again

Bob
 
I had the same issue 8 years ago when a new door entry system was fitted by my parking spot at home. Followed the advice on here and disconnected the RF lead and magic! problem solved. The fob still works close to car and I can tell when the battery in the fob is getting low as it won't work from the passenger side but still works next to the receiver. No problem but then I get dirty looks from the long hard colonel as even after 30 years I still open the car door for her first. (Those married men men will know the look there is no reply to) never spent any more money on an upgrade as that's another look that I need to save for when I need essential parts.
 
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