The Diesel Stop banner

1 - 12 of 12 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter #1
Hey guys, our 2000 7.3 keeps draining the batteries after a few days. Come to find out there is 5 volts constantly on the “S” wire on the stater relay. So came back to fuse #20 under the dash and it has 5 volts on it there a well on the left side of the fuse. When I turn the key over, I do get 10 volts on the right side of the fuse. I unplugged the clutch sensor and still 5 volts. I even unplugged the wires going to the ignition switch. Any ideas where I should check next?
 

·
Premium Member
Joined
·
15,029 Posts
That wire should start at the ignition switch. That would almost suggest another wire has crossed it at some point and they are touching. That, or some branch circuit is backfeeding through a resistor (like a bulb) into that branch. I don't have the wiring schematics for a pre 02-03, but that's what you're going to need to get all the other circuits on that fuse.

I see in the owner's manual that the fuse feeds the starter relay and clutch switch. The clutch switch also breaks the cruise control circuit. That might be the issue. See if the voltage goes away at the fuse box when you unplug the clutch switch. You will need to test with the fuse out and find which side is the feed and then test the other side.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #3
ok thanks. With the fuse out, and the transmission switch unplugged, still getting 5 volts. I will try to search the net for some prints to find out what else crosses that #20 fuse's path.

Thanks for the info.
 

·
Premium Member
Joined
·
15,029 Posts
Where are you getting 5 volts? At the solenoid? That's not where I suggested you measure. There are two sides to the fuse. One is the battery side - one is the solenoid side. To rule out the cruise as being the source of the 5 volts, I wanted you to measure the solenoid side in the fuse box with the clutch switch out.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #5
with the key off, I am getting 5 volts on the left side and 0 volts on the right side of fuse #20 (and 5 volts on the "S" wire on the starter relay when the key is off, but 12 volts when the key is turned to start). When I try to start the truck, I get 12 volts on the right side.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #6
So I started pulling each fuse independently and when I pulled fuse #15 (5amp), it killed the 5 volts. So now trying to figure out figure out GEM, PCM, Anti-Lock Brake system, Cluster and PCM Keep Alive memory. Probably something so simple but takes hours to find.
 

·
Premium Member
Joined
·
15,029 Posts
That tells me the power is back feeding. Probably through the PCM into the cruise circuit. Do you know anyone else with a 7.3? You could try swapping PCMs as a test.


Sent from my iPad using Tapatalk
 

·
Registered
Joined
·
8 Posts
Discussion Starter #8
well, I have 2 other sons with 95 and 96 7.3's, but those PCM's are not very easy to change out. Providing you are talking about the PCM that is along the drvierside fender/firewall, clear back in the corner.
 

·
Premium Member
Joined
·
15,029 Posts
Yes. Congratulations on raising your kids right! Those won't work though - need a 99-03 PCM for the test.
 

·
Registered
Joined
·
12 Posts
Hey guys, our 2000 7.3 keeps draining the batteries after a few days. Come to find out there is 5 volts constantly on the “S” wire on the stater relay. So came back to fuse #20 under the dash and it has 5 volts on it there a well on the left side of the fuse. When I turn the key over, I do get 10 volts on the right side of the fuse. I unplugged the clutch sensor and still 5 volts. I even unplugged the wires going to the ignition switch. Any ideas where I should check next?
Are you checking the stud on the relay or the wire? Could be a corroded connection. Similar problem solved by removing and scraping corrosion from the contact area of the wire connection.
 

·
Premium Member
Joined
·
9,458 Posts
I have also found that when you find voltage in a place that there shouldn't be any voltage that you need to check your grounds
 
1 - 12 of 12 Posts
Top