Hello there C5'vers once again,
working on a friends '99 Vert, auto; problem is the battery will go dead almost overnight.
I connected my DMM up and sure enough there is a pretty good draw of just about 0.5 amps after 5 minutes and still there after 20 or so.

Only by removing fuse #23, BCM 2 will the current draw drop down to around the normal 20mA or so from the 0.5 amp level.

I have removed the BCM and checked for any signs of corrosion; found nothing. I have reflowed the solder of the three connector pins and looked over the board for any cold joints or cracks; found nothing.

I have not re-installed the BCM yet to see if I did anything yet....will do that tomorrow.

Assuming the problem is still there....what next?

Thanks,
LannyL81

 

May be the BCM may be powering a relay when it should not. Start by seeing if any I/P fuse box relays are chattering there or are warm to the touch. If you don't find or hear anything I would start pulling the relays to see if you can find the issue.

Let us know and we'll go from there

 

UPDATE:
Well looks like I found the solution; I removed the BCM from the housing and got the ole magnifying glass out and scanned the solder joints, found a few that were a bit suspect. So I reflowed all the connector pin joints and then the pins of one component. Sure gotta be careful with the surface mounted caps and resistors....they will not take too much heat.

Anyways.....plugged the BCM back in and lo and behold the current draw dropped below 0.5 amps after less than a minute and continued to drop over the next 30 seconds to about 20 mA...YES!!!!!

Disconnected the battery and waited a couple of minutes and tried it again.....samething...YES.
Opened one of the doors, current draw went up like it is supposed to, shut the door and I watched the current drop after about 30 sec or so.

Did each door twice and everytime all was good.

So guess it was one or some of the many solder joints I reflowed....I am calling this one FIXED!

Now on to the HVAC display that has gone dark.....

I just may have to get that 2004 Z06 I have been wanting afterall.....these C5's are not all that difficult to work on.

Thanks guys for the help.

 

Very surprised solder joints would have caused a draw instead of just preventing a function to perform.

 

I think the bad solder joints were preventing some "function" to perform; most likely the one component that I reflowed was not working and so the firmware in the BCM did not go past this point.

Or maybe the serial communications was marginal and reflowing of the connector pins fixed it.....IDK....I am just pleased that all seems to be working now.

I am going to keep testing the car before giving it back to its owner as he is about 100 miles away and all. I have also reflowed the solder on the HVAC controls hopefully to fix the dark display....will be trying that today.

Later.

 

It would have to have been something that prevented it from fully going into "sleep" mode in my opinion.

 

If you open the HVAC module, you will see a gang of surface mount resistors on the center of one of the boards. You just have to reflow those resistor joints and you will be back to gold again.

- HVAC Module Dark Display FIX! http://forums.corvetteforum.com/c5-t...splay-fix.html

I just did this on my 02 Z a month ago and was successful.


Bill

 

UPDATE #2:
Forget everything I wrote about the solution; the problem turned-out to be the glove box light!!

I had put eveything back together and checked the current draw only to find that it was a steady 0.5 amps again!

Pulled fuse #23 and current draw did not change!!!....
Maybe its a bad wire going into the BCM...wiggled everything....no change.
So I started looking around and checking everything....the glove box was locked, but I probably pushed on it without really knowing I did...and when I looked at the current draw again, it was down. Opened one of the doors and after a short while curent dropped again like it is supposed to.

So I opened a door and started looking again. Current stayed high again.....took driver's door panel off thinking perhaps lock switch although the lights go off.....nothing there.

Checked the sun visors....nope they are off.

Which lead me to the glove box again. I unlocked it, opened the door and then held the light button in and watched the current drop to .23 amps.....waited awhile and it slowly dropped....down to about 20 mA.

The glove box door has just enough warp to it that I think the light does not always go off. I took the $@&**$$%% bulb out!!!

All seems fine now. Oh well....did the fix on the HVAC SMD resistors and the display is working again.

Putting it back together and giving it back to the owner tomorrow....without the glove box light bulb!! Also telling him to get a battery tender if he is going to let the car sit for weeks at a time.

Thanks to one and all....may be I will just keep my '96 afterall.......

LannyL81

 

I haven't checked the glove box light, but my battery goes down in two days. I'm on my fourth battery in two years. All kinds. Also, I tried it on a battery tender. With the battery tender, it took a week to kill the battery. I put an ammeter between the negative post and then negative cable and plucked one fuse and one relay at a time. current draw never changed. Wherever the current draw is coming from, it's not fused. I also disconnected the alternator completely - no change in current draw. The only way I can keep the batter charged is with a good quality processor based battery charger set to 20 amps. My next step will be to install a bettery switch and do without all the memories the car has!

 

also disconnected seats and headlights and pulled the headlight control unit. No change in current draw.

 

The B+ connector on the eng compartment Fuse box has a stud and two cables on it. Pull the two cables off the B+ stud and use a bolt to connect the two cables together isolating the eng comp fuse box.

If the current drops way down, its caused by a circuit coming from the engine fuse box. If it stays the same or only drops a small bit, its coming from the pass comp fuse box.

How much current is it drawing when the car is shut down??????????


Bill

 

Outside the meter's limits - OD (overdraw) I've already removed every relay and every fuse from BOTH fuse boards without a reduction in draw. That makes me suspect the ECU isn't going to sleep for some reason.

 

Please seperate FUSE BOXES!! You can even put the anp meter between each fuse box and see what it pulls.

Until you do that, youre not going to find it easily.

BC

 

That'll be next. Took the ECU out to examine board, knowing the inside of the car has been wet. It had a detached rear glass when I bought it! It has one electrolytic capacitor - 82 microfarad 50 volt - and I ALWAYS suspect electrolytics (a carryover from my juke box business days)! So I'm replacing that before further testing.

 

I replaced the electrolytic capacitor in the ECU and presto! No more battery drain!

 

Please post a picture of the PCM board and the capacitor location.

I know about those type capacitors since I have a number of 50's jukeboxes and newer pinball machines.

 

Wish I could, but I've already re-assembled the ECU and re-installed it. It's easy to find though: it's the only can on the board! Wish I still had some of my fifties jukeboxes, but the organization persuaded me to sell everything for 60 cents on the dollar in 71.

 

By "ECU", I assume you are referring the to Body Control Module (BCM)?

 

Well,,,Heres a pic of the PCM out of the box. My guess is that he ment to say PCM which is an ECU in most other vehicles including the C6.

Power Train Control Module (PCM)



Heres a blurry picture of the Body Control Module board out of the box.

 

Here's the part that has ME confused.