P38A Electrickery,pain in the RRR's

tomcat59alan · Aug 15, 2021

After completing the welding on one side of the car I reconnected the fully charged battery and saw a small spark when i connected the earth, put a clamp meter on the positive lead to the starter motor and it showed .10 of an amp,the lead to the ECU showed the same,the one to the fuse box showed .50 this remained the same when I removed each fuse and relay.i had latched the driver's door and put a bonnet catch in to trick the car that everything was closed before locking it. I did wait for some time to let it go to sleep. No change in the reading when I pulled the driver's seat fuses. I even removed the positive and negative feeds for the accessory tow socket.any help would be appreciated

Grrrrrr · Aug 15, 2021

I cannot recall how much the BECM drawa. Is it something like 130mA dropping to 35mA after 20 minutes when it goes ro sleep?

I haven't forgotten your clips. I just need time when it isn't raining to try and get it apart.

kermit_rr · Aug 15, 2021

I had something similar a while back. A BIG spark when i reconnected. I thought 'oh bother' and carefully disconnected. Checked and rechecked everything i could and saw nothing obvious so gingerly reconnected again. Nothing, zilch!

tomcat59alan · Aug 15, 2021

kermit_rr said:
I had something similar a while back. A BIG spark when i reconnected. I thought 'oh bother' and carefully disconnected. Checked and rechecked everything i could and saw nothing obvious so gingerly reconnected again. Nothing, zilch!

I'll have to reconnect and say oh bother instead of a mouthful of F'and C's with a couple of B's

kermit_rr · Aug 15, 2021

You called Charlie Brown, Fat!?

tomcat59alan · Aug 15, 2021

kermit_rr said:
You called Charlie Brown, Fat!?

Something like that.

Marshall8hp · Aug 15, 2021

You expect a spark when you connect up the battery again. It is normal. If you don’t get one, then start to worry.

There should be no current going to the starter unless you are starting the car. None at all, so there is an issue here.

The BeCM goes to sleep in exactly 2 minutes after locking the doors, if not, then there is something keeping it awake that you need to find.

Silly (but pertinent) question. How reliable is your clamp meter? In my experience they are very good at giving spurious results at low current draws. for the current you are talking about, use an ammeter in series with the battery. Most digital ones will do 10A without trouble, and much more reliable than a clamp meter.

By the way, has your battery gone flat?

tomcat59alan · Aug 15, 2021

Marshall8hp said:
You expect a spark when you connect up the battery again. It is normal. If you don’t get one, then start to worry.

There should be no current going to the starter unless you are starting the car. None at all, so there is an issue here.

The BeCM goes to sleep in exactly 2 minutes after locking the doors, if not, then there is something keeping it awake that you need to find.

Silly (but pertinent) question. How reliable is your clamp meter? In my experience they are very good at giving spurious results at low current draws. for the current you are talking about, use an ammeter in series with the battery. Most digital ones will do 10A without trouble, and much more reliable than a clamp meter.

By the way, has your battery gone flat?

Answer in reverse order.no the battery hasn't gone flat,I don't know how reliable the meter is it's my friends and he bought it a few months ago, I'll try my multi meter in series. Just to add I disconnected the alternator as well in case there is a diode problem. Would I be better taking all fuses and relays out of the fusebox instead of pulling them one at a time? Thanks.

pwood999 · Aug 15, 2021

Make sure you zero the clamp meter a couple of times. My amazon £30 one is quite sensitive to the closure of the clamp, and often takes several goes to zero it.

tomcat59alan · Aug 15, 2021

pwood999 said:
Make sure you zero the clamp meter a couple of times. My amazon £30 one is quite sensitive to the closure of the clamp, and often takes several goes to zero it.

Thanks Pete.

Gord Wedman · Aug 15, 2021

tomcat59alan said:
Thanks Pete.

I would not use a clamp meter for detecting low currents unless you have one specifically made for that purpose. It is hard to accurately measure half an amp, or less, with a meter designed to measure hundreds of amps. A clamp meter for low amps will have much smaller jaws capable of taking a maximum wire size around 12mm.

tomcat59alan · Aug 15, 2021

Gord Wedman said:
I would not use a clamp meter for detecting low currents unless you have one specifically made for that purpose. It is hard to accurately measure half an amp, or less, with a meter designed to measure hundreds of amps. A clamp meter for low amps will have much smaller jaws capable of taking a maximum wire size around 12mm.

Your probably right, this is what I have been using

P38A Electrickery,pain in the RRR's

tomcat59alan

Well-Known Member

Grrrrrr

Technician, Bodgit & Scarper Ltd

kermit_rr

Very

tomcat59alan

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kermit_rr

Very

tomcat59alan

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Marshall8hp

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tomcat59alan

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pwood999

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tomcat59alan

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Gord Wedman

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tomcat59alan

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