P38A Fobbed-off 2000 Vogue 4.6

There are a whole list of 'activation' inputs that will wake the BECM up - not just the RF - hence why it's worth checking to see if the BECM is actually sleeping and if it is being woken up still, even with the RF receiver disconnected.

12.6V is normal for a fully charged 12V battery, should be seeing about 14.1V when charging.

The bonnet latch can be disconnected to stop that warning - but the BECM will still go to sleep with the bonnet open. It should sleep after a couple of minutes with no activity, as a lot of the activation inputs will wake up the BECM on a change of state. So as long as it sits for a couple of minutes to time out it should still sleep.

You should get a current draw of down to approx 0.03A (30mA) once it's fully asleep.

martyuk said:

There are a whole list of 'activation' inputs that will wake the BECM up - not just the RF - hence why it's worth checking to see if the BECM is actually sleeping and if it is being woken up still, even with the RF receiver disconnected.

12.6V is normal for a fully charged 12V battery, should be seeing about 14.1V when charging.

The bonnet latch can be disconnected to stop that warning - but the BECM will still go to sleep with the bonnet open. It should sleep after a couple of minutes with no activity, as a lot of the activation inputs will wake up the BECM on a change of state. So as long as it sits for a couple of minutes to time out it should still sleep.

You should get a current draw of down to approx 0.03A (30mA) once it's fully asleep.

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Ahhhh.... didn't know the thing would sleep with the bonnet open. I can go check that today in the daylight.
Engine running Volts are 14.3v and shortly after engine off the volts drops to 13.2 and then to 12.6V so presumably the battery is still fairly healthy.
My ring meter isn't sensitive enough (its range is 1,000A /400A/40A) but it does show a huge drop as soon as the doors are locked, from 3Amps to 0.1A and remains pretty much around there.
With the bonnet open I pulled every fuse in the main fusebox 1 by 1 (except the big blade fuses) but the reading never changed. Will have to try the second fusebox under the seat.
Really interesting to see that in Ignition pos 2 the brake-booster pump started and the reading jumps to c. 30A draw. I will monitor the voltage every day and see what happens now the RF unit is out of circuit.
Thanks again!

DanClarke said:

If I could bypass the bonnet switch I could put a ring-ammeter on the main battery lead and see what happens as it goes to sleep/wakes up.

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Can you attach some jumpleads to the battery and drop them down through the engine bay and ut the bottom and attach the ammeter there?

Grrrrrr said:

Can you attach some jumpleads to the battery and drop them down through the engine bay and ut the bottom and attach the ammeter there?

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In this case as it was a ring-clamp ammeter I am afraid I can't. The ring goes round the earth or +ve battery main lead. The attraction of this style of ammeter is that you do not have to disconnect the battery at all.

DanClarke said:

Ahhhh.... didn't know the thing would sleep with the bonnet open. I can go check that today in the daylight.
Engine running Volts are 14.3v and shortly after engine off the volts drops to 13.2 and then to 12.6V so presumably the battery is still fairly healthy.
My ring meter isn't sensitive enough (its range is 1,000A /400A/40A) but it does show a huge drop as soon as the doors are locked, from 3Amps to 0.1A and remains pretty much around there.
With the bonnet open I pulled every fuse in the main fusebox 1 by 1 (except the big blade fuses) but the reading never changed. Will have to try the second fusebox under the seat.
Really interesting to see that in Ignition pos 2 the brake-booster pump started and the reading jumps to c. 30A draw. I will monitor the voltage every day and see what happens now the RF unit is out of circuit.
Thanks again!

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No problem..

14.3 when running is good - and 12.6V with engine off sounds good aswell.

I usually just use a multimeter with a couple of crocodile clips on the test leads. With a bit of care you can do it so you can get it in line without losing battery power. My meter goes up to 10A - which is fine as long as you don't turn the ignition on! But it does mean it will read below .1A

The ABS pump does draw a fair wahck on startup alright - hence why it has the special relay (It's got double contacts inside it, to carry the current of the motor!)

Post back with the results after a few days - will be interesting to hear how it's doing..

Marty

Quick laughable update.
Despite it all working quite happily earlier today without the RF unit installed...I jumped in it tonight and it said "Engine Disabled" press fob.
So I went off in the french POS instead. Will reconnect the RF unit tomorrow. LOL

DanClarke said:

Quick laughable update.
Despite it all working quite happily earlier today without the RF unit installed...I jumped in it tonight and it said "Engine Disabled" press fob.
So I went off in the french POS instead. Will reconnect the RF unit tomorrow. LOL

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If you have nanocom, disable the immobiliser until you get the battery drain fixed. Then you won't get engine disabled messages

Good idea

So, the Jog-Unit arrived today. I opened the packaging only to read on the blurb the dreaded numbers 433 and the word Mhz.
Went back and looked at my order and there in BIG RED letters is 315Mhz. Customer service ticket raised.
You couldn't make it up.
Put the RF receiver back on this morning for convenience sake.
Battery Volts were down at 12.1V so it seems there is a drain somewhere and it may not be the RF unit continuously waking the BeCM. But something else entirely.
After running the vehicle for 10 minutes this morning and it being charged up at 12.6V it was down at 12.3V at 6:30 this evening.
Sat in it this evening and the RED-LED glow in the PARK position of the gear selector goes out after 2 mins or so and stays out. Well for as long as I sat in there (10 mins).
I may put a camera in there to monitor it for a few hours just to see if we have 2 things tripping the BeCM awake.

You know, it's not unheard of for new batteries to fail.
Try disconnecting it and charge it overnight then without reconnecting it, see what voltage you get in the evening.
If it stays up then it's drain, if not I'd be trying to get another under warranty.

Wazzajnr said:

You know, it's not unheard of for new batteries to fail.
Try disconnecting it and charge it overnight then without reconnecting it, see what voltage you get in the evening.
If it stays up then it's drain, if not I'd be trying to get another under warranty.

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Good Call. Will give it a go. Have Nanocom and an absence of fear lol.

DanClarke said:

So, the Jog-Unit arrived today. I opened the packaging only to read on the blurb the dreaded numbers 433 and the word Mhz.
Went back and looked at my order and there in BIG RED letters is 315Mhz. Customer service ticket raised.
You couldn't make it up.
Put the RF receiver back on this morning for convenience sake.
Battery Volts were down at 12.1V so it seems there is a drain somewhere and it may not be the RF unit continuously waking the BeCM. But something else entirely.
After running the vehicle for 10 minutes this morning and it being charged up at 12.6V it was down at 12.3V at 6:30 this evening.
Sat in it this evening and the RED-LED glow in the PARK position of the gear selector goes out after 2 mins or so and stays out. Well for as long as I sat in there (10 mins).
I may put a camera in there to monitor it for a few hours just to see if we have 2 things tripping the BeCM awake.

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Might not be too bad. Jog switch only triggered for a second, isn't it?!

Grrrrrr said:

Might not be too bad. Jog switch only triggered for a second, isn't it?!

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Yup.

Hi Grrrrrr,
I opened the jog unit up and took a look inside.
While the paperwork instructions clearly says 433Mhz the crystal oscillator can has 4.897 printed on it and that is indeed the frequency used for 315Mhz so maybe it is just the enclosed leaflet that's wrong.
But yes, you are right if it only jogs for a short-time it could be ok anyway.

A further little twist........
I was out in my little workshop today and the Rangie is less than 6 feet from the open roller-shutter door.
While pottering around sorting out some parts for the new trike I am building I heard all the door-locks on the car cycle as one "Chunk-Chunk",
Went to the car and found all the doors unlocked.
Interesting....... as both of the keys were indoors on my desk in my study and no-one had been in there or touched them, AND, the aerial lead to the RF unit is OFF and you need to be up against the rear quarter light glass to get the fobs to work.
So, I went indoors and retrieved a key and put it in and to Position 1. Little doo-dad in the cigar lighter sprang to life and informed me that the battery volts were down at 11.6V.
Now, I know if the battery is screwed you can get odd happenings on the console display (0-RPM, no speedo etc.) while you are driving along......but really? The car can decide to unlock itself?
Sounding more & more like a dodgy battery to me. Not a cheap swap-out by any means though for a decent CCA and AH battery. Ruddy stealer swore blind that this was a brand new battery in July. LOL

Was it unlocked before, so the clunk-clunk was the locks locking themselves and then re-unlocking?

Sounds like one of the CDL microswitches in the latch is starting to become intermittent to me. Also a bad microswitch is known to cause battery drain...

martyuk said:

Was it unlocked before, so the clunk-clunk was the locks locking themselves and then re-unlocking?

Sounds like one of the CDL microswitches in the latch is starting to become intermittent to me. Also a bad microswitch is known to cause battery drain...

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Hi Marty,
I agree, the double-clunk would suggest it was a lock/unlock cycle. I'm fairly sure I locked it up on last usage.
Are the CDL microswitches on the drivers door only or on both front doors? I wonder how much a new set are?
I might try pulling the door card off and giving it all a good clean with contact cleaner and a light oiling on the non-switch parts.

There are microswitches inside all of the door latches - but CDL switches to control the central locking are only in both front doors.

The RHF one is the best bet to start with, as it is the ground path (when unlocked) for the tailgate motor, so has more current passing through the contacts than the LHF latch does.

The only downside, the switches are INSIDE the latches, and on later P38's, from somewhere around mid '97 onwards, the microswitches are all moulded together, so the internals aren't serviceable and they are a pain to change as you can buy just the blocks of switches.

All of the latches that I refurbish are modified slightly to allow me to fit standard microswitches (like the original P38 latches had!). I would offer to supply a refurbed RHF latch at least, but I'm away for work a lot in the coming months, so not going to have time to work on much P38 related things until the New Year now..

I eventually got round to doing a full charge on the battery (Duracell 110AH 720CCA) and then just disconnecting it on the Earth side and measuring to see if there was any volts drop over time.
The answer was that the only volts drop was 0.52V the most of which (0.41V) happened in the first hour after the charger was disconnected.
It has now been disconnected for 24 hours and the total volt drop is only 0.52V including that initial "settling" and I would put that down to battery temperature fluctuations rather than any significant internal losses.

So, as the battery typically drops 1 volt a day e.g. from 12.6 to 11.x in 24 hours when connected to the cars systems I would think that it has to be a parasitic drain or the dreaded BeCM cycling due to spurious wake-ups from stuff on the 433Mhz band.
Time to fit the 3.15Mhz jog-unit (which is definitely 3.15Mhz even though the user pamphlet says 433Mhz; I know because the crystal clock can has 4.897 printed on it).
So a combo of RF wake-ups and spurious/parasitic loads is my guess.
As I sometimes get door-lock cycling while driving and even when the car is sat stood still. I am suspecting its a microswitch problem and nothing more. But as that can burn out the door-lock motors its a pain.

Hang on a sec.

So you STILL think it is RF waking it up, even when a post up above that you reconnected it for convenience, and then actually sat in it and then observed the P LED and it didn't come back on to show the BECM was being woken back up.

If you had a RF drain problem on a NEW battery, which you have pretty much proven and happy with that it's holding charge, then it still shouldn't struggle to start the next morning unless the BECM is never sleeping (which you've proven it is)

Now you are mentioning door locks jumping whilst driving and occasionally whilst stopped - and even when you were away from the vehicle.
As I said in my last post, bad door latch microswitches are KNOWN to cause parasitic battery drain. One owner who had had was observing 500ma constant drain, even though the BECM was sleeping.

Do you know exactly what the drain is? as far as I can see you've done a lot of testing on the battery, but not actually put a current meter in series with one of the battery terminals to measure the exact drain. I don't believe that a current clamp meter is going to give enough of an accurate readout, at that low current on DC to figure out what's going on. You NEED to put the ammeter inline.

Then you'll see if you have a parasitic battery drain, which is constant when the BECM is asleep, or whether you have a spurious drain as the BECM is woken up (the current dropping to normal sleep current of about 30mA and then bouncing back up to around 1A as the BECM is woken up). This test is easy to repeat with the RF receiver both connected and totally unplugged - it will be pretty obvious then if there is an RF problem causing it.

Before p*ssing about with additional RF units, I'd replace the door latch as a) Chances are it could be causing a constant parasitic drain on the battery, b) jumping locks is a known sign that at least the CDL microswitch is intermittent or faulty and c) it can lead to another whole world of headaches if you find you need to use the door lock at some point for EKA or the likes, and then find out your microswitch is dead, or not reliably triggering.

I would do the current draw tests with a multimeter inline to determine what you ACTUAL current draw is, and look at replacing the door latch before mucking about with addition RF stuff, as I'm almost certain the problem will still be there afterwards.