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If the battery is ok off the car then you need to check its going to sleep then measure the draw.
P38A Fixed- Battery going flat again
- Thread starter Andy Burrell
- Start date
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- 19,297
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- Buckinghamshire, UK. ('95 DT)
After market stereo? Headlight wipers parked? Anyone been fiddling with towbar electrics?
Eric the Car Guy on YouTube does a good guide on looking for battery drain. I used jump leads so I could shut the bonnet but you can jam the bonnet switches with something to leave it open.
Eric the Car Guy on YouTube does a good guide on looking for battery drain. I used jump leads so I could shut the bonnet but you can jam the bonnet switches with something to leave it open.
Andy Burrell
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Yeah, found him this morning.
The towbar plugs are pretty manky and as I don't use it will see if I can remove them easily. Std stereo, will check the headlight wipers.
I took some current readings before I took the battery off .
There is a 0.4a reading once the BECM has gone to sleep.
With the engine running but no other load it's 23.8a
With the engine running and everything on its 91.5a
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- Buckinghamshire, UK. ('95 DT)
Check RAVE but I think that is a bit high. The value for when BECM is asleep might be around 125mA but check RAVE to be sure.
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Where are you taking those readings? At the battery +ve or the alternator +ve?
Datatek
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0.4a is way too high, when the BECM goes to sleep it should be 30 to 50ma (0.030 to 0.050a)
Andy Burrell
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Charged the battery yesterday and then left it on the bench overnight it showed 13.3v and this morning 13.1v so that suggests the battery is OK. Going to reconnect it later and see if I can eliminate things. All good fun
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It takes a while, but just pull different fuses & then see what current is in sleep mode. Alternatively lift the fusebox up, and measure currents on the various feeds from fusebox while it's asleep.
Andy Burrell
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The current draw is 3.5a when the BECM is awake and 170ma when it's asleep so too high. It drops from 3.5a to 660ma initially then after another couple of mins drops to 170ma.
So pulling fuses now.
Andy Burrell
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So none of the under bonnet fuses are causing an issue but as soon as I pull F14 the current draw drops to 24ma so looks like that's the culprit. Will have to look it up now.
Andy Burrell
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F14 feeds a bunch of stuff. As well as Trailer wiring module, check CD Changer is shutting down ?
It also seems that F14 feeds RL6, but this is showing two separate functions in RAVE. Fuel Flap & Aux Relay, but these are different functions ?? also appears to be used by BECM for rear door latches.
Depends if your is GEMS or THOR.
It also seems that F14 feeds RL6, but this is showing two separate functions in RAVE. Fuel Flap & Aux Relay, but these are different functions ?? also appears to be used by BECM for rear door latches.
Depends if your is GEMS or THOR.
Andy Burrell
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Looks like it's the towbar, removed the shoddy connections behind the nearside rear light and the current draw seems to have stopped. This feed goes to a grey plug that I think is only used for caravans. It's all disconnected now so am quite hopeful it's the issue.
Will need to see now it is once its been standing a few days.
Last edited:
Datatek
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There are proper connection points for trailer sockets, no need for all that stuff as the BECM recognises when a trailer is connected and flashes a trailer sign on the dash when the indicators are used.
Andy Burrell
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It was a complete bodge up wires chopped into and scotch lock connectors plus the uninsulated circuit board just stuffed in the back of the light fitting. The other side is also scotch lock connectors but nothing else, they have spliced into the wires going to the connector for the RR towbar electrics plug. It does work as tried my light board on it. Didn't look to see if the dash light flashed.
Grey one is 12S socket. Feeds caravan internals & reversing light.
Black is 12N & that's the caravan/trailer road lights.
Andy Burrell
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It was the grey one and it's associated mess looking like the issue. Don't normally tow with the P38 as my car tows my trailer well enough.
dubbleRR
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might have been a split charger for caravan battery 
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Andy Burrell
Retired to the country
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Just tested my lighting board to see if the trailer light on the dash flashes and it doesn't. The lights etc work but what a pain. Had a look online but the correct cable doesn't seem to be listed anywhere so will have to look out for a used one.
Started OK this morning will have to wait until Wednesday to be sure it's fixed though.
