Parasitic Draw
May 24th, 2019, 10:12 PM
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Parasitic Draw
2007 3500 LMM Express Cutaway Parasitic Draw
I have a 2007 Express Cutaway that’s a Thomas Built short bus. I have a parasitic draw that’s draining the battery in a day or two. It’s drawing 2 Amps.
I’ve worked on tracking it down as follows:
Measuring current flow through the engine compartment negative cable while pulling each fuse one at a time starting with the bus body, then the fuse block under the seat,’then the fuse block under the hood. No change.
I disconnected the fusible link on the under hood block. No change.
I disconnected the primary wire from the under seat fuse block. No change.
I traced the cable for the wheelchair lift and disconnected it. No change.
Then I decided to work from the positive side. There are several hots connected under the hood. I’ve tentatively identified these as Wheelchair Lift, Bus Body, Cutaway Van Starter/Under Hood Primary/Interior Primary.
I separated each of these, except for the “Cutaway Van” part where the interior/under hood/starter are part of a factory made inseparable cable.
The bus body, no current.
The wheelchair, no current.
The “cutaway van” current.
So focusing on the Cutaway:
Disconnected the primary to the under seat fuse block. No change.
Pull each fuse one at a time and each relay one at a time from the under hood fuse block. No change.
Disconnect one side of the fusible link on the under hood block. No change.
So that’s where I’m at.
Is the alternator fused through the fusible link?
If anyone has ideas for how I can proceed to test further, please let me know!
Thank you!
Danjo
May 24th, 2019, 11:00 PM
#2
May 25th, 2019, 11:57 AM
#3
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That kind of thing caused me so many problems over the last three years. When it first began, I think it was simply a cell charger. The first time I drained my batteries. Then there was a problem where the power door switch lights would stay on, slowly draining the battery. I never figured that out, but the amount of down time was crippling when it happened. Fixed now. Then intermittent problems with temporarily wiring in an audio system that never gets finished. Anyways, those problems are sorted at the moment, but all I can say is good luck.
May 25th, 2019, 7:04 PM
#5
According to the ASE, most vehicle manufacturers specify a parasitic drain no greater than 0.03A.
May 25th, 2019, 10:28 PM
#6
I'm here for the party
i know you said you checked the lift but i just cant forget about my mom's 99 e150 with a wheelchair lift. i couldnt find the drain on the battery till i pulled the 5 amp fuse on the lift for the lift, problem was gone. i wired up a light switch that she could turn the lift on and off from the back door. she took it to the company and they said there was nothing wrong with it, but if you leave it on overnight it will kill the battery. i want to say it also was around 2-3A draw
May 27th, 2019, 6:45 PM
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2007 3500 LMM Express Cutaway Parasitic Draw
I have a 2007 Express Cutaway that’s a Thomas Built short bus. I have a parasitic draw that’s draining the battery in a day or two. It’s drawing 2 Amps.
I’ve worked on tracking it down as follows:
Measuring current flow through the engine compartment negative cable while pulling each fuse one at a time starting with the bus body, then the fuse block under the seat,’then the fuse block under the hood. No change.
I disconnected the fusible link on the under hood block. No change.
I disconnected the primary wire from the under seat fuse block. No change.
I traced the cable for the wheelchair lift and disconnected it. No change.
Then I decided to work from the positive side. There are several hots connected under the hood. I’ve tentatively identified these as Wheelchair Lift, Bus Body, Cutaway Van Starter/Under Hood Primary/Interior Primary.
I separated each of these, except for the “Cutaway Van” part where the interior/under hood/starter are part of a factory made inseparable cable.
The bus body, no current.
The wheelchair, no current.
The “cutaway van” current.
So focusing on the Cutaway:
Disconnected the primary to the under seat fuse block. No change.
Pull each fuse one at a time and each relay one at a time from the under hood fuse block. No change.
Disconnect one side of the fusible link on the under hood block. No change.
So that’s where I’m at.
Is the alternator fused through the fusible link?
If anyone has ideas for how I can proceed to test further, please let me know!
Thank you!
Danjo
Hello All,
i did some more troubleshooting today. 2.5 Amp Draw. I went back to pulling fuses and found when I pulled one, the draw dropped a few 10ths of an amp. I looked at the legend and found it labeled TCM. Then I found two others labeled TCM1 and TCM2, so I pulled those. Then it said .5 Amp Draw. While I was looking at it, that disappeared. I thought I was having problems with my multimeter connections so I disconnected and reconnected. .5 Amps. Then 60 seconds later, 0 Amps. So I have surmised that something wakes up for 60 seconds and then sleeps again. But then there’s the other 2 Amps.
A quick Internet search says it’s the BCM. I found the BCM behind the passenger side dash panel. I reinstalled the fuses and disconnected the BCM connectors and test again. .5 Amps for 60 seconds and then 0 Amps.
so is it the BCM that’s bad or something downstream? I see posts on the Internet that say it could be both. Is there a way to test? With the multiple connectors is there a way to isolate?
thank you everyone for taking the time to help!
Danjo
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May 27th, 2019, 9:15 PM
#9
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Well, I guess that’s what I’m trying to find out from someone familiar with that BCM. I suppose it’s worth 20 bucks to have a look at the wiring diagrams on the ACDelco site.
In the meantime, if anyone out there knows if Draw from the Fuses for the BCM could be something downstream please reply back.
thanks!!
May 27th, 2019, 11:53 PM
#10
to clarify: the 3 fuses that you pulled that stopped the draw are:
tcm
tcm1
tcm2
located in which fuse box?
...but the internet says the bcm is the problem...do I understand this correctly.
tcm
tcm1
tcm2
located in which fuse box?
...but the internet says the bcm is the problem...do I understand this correctly.