Electrical problems, where to start?

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quavey said:
I'm now really looking to find the battery drain as well as it shouldn't be pulling as much as it is. Are there common culprits to look for? Am I going to damage anything by pulling fuses out and seeing the effect?

Should I have a look at the relays as well?
Click to expand...
On the P38, the RF receiver keeping the BECM awake is the common culprit. Have you done the BECM sleep test?
You could check the headlight wipers are parking properly and also that the heater fans actually turn off with the ignition.
You can get a little test plug to replace a fuse which allows you to put an ammeter in place of the fuse so you can check fuse by fuse for drain.
 
Datatek said:
On the P38, the RF receiver keeping the BECM awake is the common culprit. Have you done the BECM sleep test?
You could check the headlight wipers are parking properly and also that the heater fans actually turn off with the ignition.
You can get a little test plug to replace a fuse which allows you to put an ammeter in place of the fuse so you can check fuse by fuse for drain.
Click to expand...

I have got the Ariel disconnected at the moment and it has been for some months.

BECM sleep test is that lock the car and keep and eye on the currant drain with the clamp meter? I can't see the light on the P position of the gearbox.

Headlight wipers are a possibility. How do I check those?

The fans are totally of as far as I am aware.

Right, Ive just been through every fuse and Relay one by one in both the underbonnet fuse box and the one under the drivers seat. Taking one out, checking the reading, replacing it and taking another out. No significant change from 0.42A (it does vary a touch from 0.39 to 0.48 but always settles around 0.42/0.44. It was never less than 0.39A and Ive seen that reading with every fuse and relay in place.

The only slight anomoly was a 30A fuse "missing" according to the diagram on the drivers seat fusebox but I couldnt see any terminals in the box so even if there was a fuse there it wouldnt do anything. I wonder if its for the Satnav that my car doesnt have?

Unlocking the car gives me about 0.96A, putting the ignition onto the first click, radio on gives me about 1.6A.
 
+1 on RF receiver if it hasn't been upgraded. It'll kill the battery overnight so you'll have to disconnect it. Brian's second fob trick works well and is cheap as chips so worth a try.

Other common culprits are aftermarket radios.
 
quavey said:
I have got the Ariel disconnected at the moment and it has been for some months.

BECM sleep test is that lock the car and keep and eye on the currant drain with the clamp meter? I can't see the light on the P position of the gearbox.

Headlight wipers are a possibility. How do I check those?

The fans are totally of as far as I am aware.

Right, Ive just been through every fuse and Relay one by one in both the underbonnet fuse box and the one under the drivers seat. Taking one out, checking the reading, replacing it and taking another out. No significant change from 0.42A (it does vary a touch from 0.39 to 0.48 but always settles around 0.42/0.44. It was never less than 0.39A and Ive seen that reading with every fuse and relay in place.

The only slight anomoly was a 30A fuse "missing" according to the diagram on the drivers seat fusebox but I couldnt see any terminals in the box so even if there was a fuse there it wouldnt do anything. I wonder if its for the Satnav that my car doesnt have?

Unlocking the car gives me about 0.96A, putting the ignition onto the first click, radio on gives me about 1.6A.
Click to expand...
If the RF receiver is faulty, disconnecting the aerial will not stop it from keeping the BECM awake.
 
+ 1 on the RF receiver.

I disconnected the blue wire, but still had issues.

So I cut the orange signal wire from the RF to the BECM, placing (for now) a manual switch in it. (I will buy a remote relay someday)

It does mean that I have to lock / unlock with the key (then press the switch and the open key on the fob), but it has cured my battery drain issue.

Having said that I've also connected a 6W solar charger up, as the P38 is my 3rd car, and I have no Garage space (taken up by Wifes's Audi and my TVR) for it to go on a trickle charger.
 
TVRConvert said:
+ 1 on the RF receiver.

I disconnected the blue wire, but still had issues.

So I cut the orange signal wire from the RF to the BECM, placing (for now) a manual switch in it. (I will buy a remote relay someday)

It does mean that I have to lock / unlock with the key (then press the switch and the open key on the fob), but it has cured my battery drain issue.

Having said that I've also connected a 6W solar charger up, as the P38 is my 3rd car, and I have no Garage space (taken up by Wifes's Audi and my TVR) for it to go on a trickle charger.
Click to expand...
I got a remote jog switch from the Bay of Flea for less than £3. Never had a problem since.:)
 
Its got an OEM stereo so it won't be that but yes its looking like it could be the radio receiver. However, Battery Megastore have agreed to replace the faulty battery so that should be better soon and then i can tackle the drain. The second remote fob solution looks to be a good one to be honest and even I might be able to do it! Cheers Brian!
 
quavey said:
Its got an OEM stereo so it won't be that but yes its looking like it could be the radio receiver. However, Battery Megastore have agreed to replace the faulty battery so that should be better soon and then i can tackle the drain. The second remote fob solution looks to be a good one to be honest and even I might be able to do it! Cheers Brian!
Click to expand...
DON'T let the replacement battery go flat or you will destroy it PDQ:eek:
 
Datatek said:
DON'T let the replacement battery go flat or you will destroy it PDQ:eek:
Click to expand...

It was never good from day one to be honest, the original 85Ah battery would last a week or 10 days without any bother, the 130Ah battery never managed more than 3 without a jump. I've just taken it of the car now and the voltage is already dropping and the green inspection window is looking decidedly dim (where as it was bright green whilst on charge).

Anyway new one should be here today (as with all the electrical problem threads it says make sure you've got a good strong battery first!) I will keep an eye on it and see how it gets on.
 
Datatek said:
Charge it before you fit it.
Click to expand...

Bit late ;) But I did check it before it went on and only 12.55v in it from new. I fitted it and started her up... sounded so much better than the old battery. It actually seemed to start like the old girl always used to.

Did all the windows and roof, then checked the battery charging voltage which was 14.5v turned the ignition of and we dropped to 12.6v and stable, rather than dropping like a prematurely removed cake from the oven like before.

Anyway the charger was still connected to the car but unplugged so i'm going to leave her on charge over night and take her of in the morning. I'll be away for work for a couple of days so I'll see how she is doing when I'm home at the end of the week.
 
Just to update this, I checked the battery voltage this afternoon and after being stood in the cold for 3 days the battery is still showing 12.61v so very very happy that it was just a totally ruined battery (4 months old!) that thankfully battery megastore replaced for me.

Long live the P38!
 
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