C5 Fuse Box autopsy
07-02-2012, 08:30 PM
#1
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C5 Fuse Box autopsy
Ok, finally got around to this....had a couple requests to show what is inside....it ain't simple!
A little background...I had a few electrical gremlins I could not figure out on my own, so I took the car in to a talented tuner near me. Long story short...rebuilt PCM, new ignition switch, and new fusebox, and a few other items, and I am back on the road and lovin' this car again. Keep in mind, I am no electrical wizard like some of the guys here, but I will try to explain a few things with the pictures.
Initial short was found here where the white paint shows one of the fuse locations we see when popping off the lid....
here is the backside and removable separator revealing the affected circuits...white paint again...
separator board removed....there is one on each side...notice all the fixed pins!
Now the fun begins....here is more of the internal stuff...
and now it is getting complicated to say the least....
All those extra little pins fell out from somewhere... What amazes me most is it looks like all that copper wiring is hand laid into the pin layout. I would shoot myself in the head before accepting a job like that
Each one is carefully inserted into a notch, while avoiding touching any other conductor on that board....what a maze! What I did learn is all fuse boxes are interchangeable for the C5....they just need to carry the correct relays and fuses for your car depending on your options, etc. We put in a new 2004 box from Bowling Green's leftover stock from when the C5 production ended. The guy I bought it from purchased all the remaining C5 parts from the plant...12 semi loads of stuff! With a picture of my bad box taken earlier we duplicated the fuse/relay layout for my 97. It solved all my problems.
A little background...I had a few electrical gremlins I could not figure out on my own, so I took the car in to a talented tuner near me. Long story short...rebuilt PCM, new ignition switch, and new fusebox, and a few other items, and I am back on the road and lovin' this car again. Keep in mind, I am no electrical wizard like some of the guys here, but I will try to explain a few things with the pictures.Initial short was found here where the white paint shows one of the fuse locations we see when popping off the lid....
here is the backside and removable separator revealing the affected circuits...white paint again...
separator board removed....there is one on each side...notice all the fixed pins!
Now the fun begins....here is more of the internal stuff...
and now it is getting complicated to say the least....
All those extra little pins fell out from somewhere... What amazes me most is it looks like all that copper wiring is hand laid into the pin layout. I would shoot myself in the head before accepting a job like that
Each one is carefully inserted into a notch, while avoiding touching any other conductor on that board....what a maze! What I did learn is all fuse boxes are interchangeable for the C5....they just need to carry the correct relays and fuses for your car depending on your options, etc. We put in a new 2004 box from Bowling Green's leftover stock from when the C5 production ended. The guy I bought it from purchased all the remaining C5 parts from the plant...12 semi loads of stuff! With a picture of my bad box taken earlier we duplicated the fuse/relay layout for my 97. It solved all my problems.
07-02-2012, 09:41 PM
#4
Team Owner
Interesting. Good pix too. 
Were you experiencing a short circuit or an open circuit? Big difference. IOW, were you blowing fuses and/or melting things, such as wires/components, etc. (short) OR were you experiencing things that simply didn't work or worked intermittently, due to lack of power (open) getting to a component/circuit?
Your problem, or experience, could prove to be a good diagnostic tool for others in the future who may experience similar problems.
Strictly judging from the pictures, I can see where the possibility of an unintended circuit path could exist (called a short) if those copper wires were not kept separated in a secure, reliable manner (poor assembly, vibration, etc) and would/could lead to a short circuit along with continual blown fuses. I could also see where the possibility of an open could exist if the wires were not inserted securely in their respective tabs/pins.
Were you experiencing a short circuit or an open circuit? Big difference. IOW, were you blowing fuses and/or melting things, such as wires/components, etc. (short) OR were you experiencing things that simply didn't work or worked intermittently, due to lack of power (open) getting to a component/circuit?
Your problem, or experience, could prove to be a good diagnostic tool for others in the future who may experience similar problems.
Strictly judging from the pictures, I can see where the possibility of an unintended circuit path could exist (called a short) if those copper wires were not kept separated in a secure, reliable manner (poor assembly, vibration, etc) and would/could lead to a short circuit along with continual blown fuses. I could also see where the possibility of an open could exist if the wires were not inserted securely in their respective tabs/pins.
07-02-2012, 10:33 PM
#5
Tech Contributor
07-03-2012, 12:06 AM
#6
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Here is what the shop stated on the invoice....along with a little more background. Bill Curlee's revelations about the ignition switch failures will come to mind.
Diagnose fuse panel problem
"Traced 12 volt source from O2 heater circuit/power supply to fuse block cavity 15. Tested power source and identified that power distribution was intact and supplying correct voltage. Determined the ground circuit for O2 sensors were intact as well. Identified failed circuit within fuse block and attempted to isolate problem within the fuse block assembly. Unable to complete failure analysis due to the fact that fuse block is non-serviceable-suspect crack in circuit plate molded plastic is the cause. New fuse block was installed and power circuit is now energized."
Knowing you guys, I am sure you would disagree the fuse block is non-serviceable
But taking it apart and trying to repair it obviously would be a nightmare when all those little pieces hit the bench.
##############
Also, I had other problems with the car. My HVAC controller was dead during the first 5 minutes of driving, then it would come on and be running fine until the next shutdown and restart. I had two spare controllers and both exhibited the problem...this stumped me....what were the odds of both being bad?
I also had a cold stumble at around 125* coolant temp from a first start overnight. Finally, my O2 sensor wires were chaffing and shorting against the heat shield. The sensor was replaced. The new PCM and ignition switch resolved problems as follows:
Diagnosis of HVAC?BCM
Intermittent failure of HVAC module and BCM controller showed that the ignition supply was compromised. Tested power supply and ground circuits and determined that there was no loss in continuity for any of them. Data stream revealed no communication with BCM as well. Tapping on the switch assembly revealed that there is a short internal to switch assembly. Completed test drive and noted that vehicle stumble was absent when computer switched to close loop and that the O2 sensors/fuel trims were reading correctly. No concerns are present at this time.
Cold stumble at closed loop
Work performed-investigate cause of trouble codes-O2 fault and MAP sensor fault. Back traced MAP sensor and found low reference for 5 volt circuit. Checked grounds and started back tracing to source. Tested PCM and found that the voltage regulation for the MAP sensor was not being interpreted by the computer correctly. When varying input voltage was provided, the PCM did not respond accordingly.
Diagnose fuse panel problem
"Traced 12 volt source from O2 heater circuit/power supply to fuse block cavity 15. Tested power source and identified that power distribution was intact and supplying correct voltage. Determined the ground circuit for O2 sensors were intact as well. Identified failed circuit within fuse block and attempted to isolate problem within the fuse block assembly. Unable to complete failure analysis due to the fact that fuse block is non-serviceable-suspect crack in circuit plate molded plastic is the cause. New fuse block was installed and power circuit is now energized."
Knowing you guys, I am sure you would disagree the fuse block is non-serviceable
But taking it apart and trying to repair it obviously would be a nightmare when all those little pieces hit the bench.##############
Also, I had other problems with the car. My HVAC controller was dead during the first 5 minutes of driving, then it would come on and be running fine until the next shutdown and restart. I had two spare controllers and both exhibited the problem...this stumped me....what were the odds of both being bad?
I also had a cold stumble at around 125* coolant temp from a first start overnight. Finally, my O2 sensor wires were chaffing and shorting against the heat shield. The sensor was replaced. The new PCM and ignition switch resolved problems as follows:
Diagnosis of HVAC?BCM
Intermittent failure of HVAC module and BCM controller showed that the ignition supply was compromised. Tested power supply and ground circuits and determined that there was no loss in continuity for any of them. Data stream revealed no communication with BCM as well. Tapping on the switch assembly revealed that there is a short internal to switch assembly. Completed test drive and noted that vehicle stumble was absent when computer switched to close loop and that the O2 sensors/fuel trims were reading correctly. No concerns are present at this time.
Cold stumble at closed loop
Work performed-investigate cause of trouble codes-O2 fault and MAP sensor fault. Back traced MAP sensor and found low reference for 5 volt circuit. Checked grounds and started back tracing to source. Tested PCM and found that the voltage regulation for the MAP sensor was not being interpreted by the computer correctly. When varying input voltage was provided, the PCM did not respond accordingly.
07-03-2012, 12:13 AM
#8
Burning Brakes
Last edited by ZedO6; 07-03-2012 at 10:36 AM.
07-03-2012, 06:51 AM
#10
Tech Contributor
Here is what the shop stated on the invoice....along with a little more background. Bill Curlee's revelations about the ignition switch failures will come to mind.
Diagnose fuse panel problem
"Traced 12 volt source from O2 heater circuit/power supply to fuse block cavity 15. Tested power source and identified that power distribution was intact and supplying correct voltage. Determined the ground circuit for O2 sensors were intact as well. Identified failed circuit within fuse block and attempted to isolate problem within the fuse block assembly. Unable to complete failure analysis due to the fact that fuse block is non-serviceable-suspect crack in circuit plate molded plastic is the cause. New fuse block was installed and power circuit is now energized."
Knowing you guys, I am sure you would disagree the fuse block is non-serviceable But taking it apart and trying to repair it obviously would be a nightmare when all those little pieces hit the bench.
##############
Also, I had other problems with the car. My HVAC controller was dead during the first 5 minutes of driving, then it would come on and be running fine until the next shutdown and restart. I had two spare controllers and both exhibited the problem...this stumped me....what were the odds of both being bad?
I also had a cold stumble at around 125* coolant temp from a first start overnight. Finally, my O2 sensor wires were chaffing and shorting against the heat shield. The sensor was replaced. The new PCM and ignition switch resolved problems as follows:
Diagnosis of HVAC?BCM
Intermittent failure of HVAC module and BCM controller showed that the ignition supply was compromised. Tested power supply and ground circuits and determined that there was no loss in continuity for any of them. Data stream revealed no communication with BCM as well. Tapping on the switch assembly revealed that there is a short internal to switch assembly. Completed test drive and noted that vehicle stumble was absent when computer switched to close loop and that the O2 sensors/fuel trims were reading correctly. No concerns are present at this time.
Cold stumble at closed loop
Work performed-investigate cause of trouble codes-O2 fault and MAP sensor fault. Back traced MAP sensor and found low reference for 5 volt circuit. Checked grounds and started back tracing to source. Tested PCM and found that the voltage regulation for the MAP sensor was not being interpreted by the computer correctly. When varying input voltage was provided, the PCM did not respond accordingly.
Diagnose fuse panel problem
"Traced 12 volt source from O2 heater circuit/power supply to fuse block cavity 15. Tested power source and identified that power distribution was intact and supplying correct voltage. Determined the ground circuit for O2 sensors were intact as well. Identified failed circuit within fuse block and attempted to isolate problem within the fuse block assembly. Unable to complete failure analysis due to the fact that fuse block is non-serviceable-suspect crack in circuit plate molded plastic is the cause. New fuse block was installed and power circuit is now energized."
Knowing you guys, I am sure you would disagree the fuse block is non-serviceable
But taking it apart and trying to repair it obviously would be a nightmare when all those little pieces hit the bench.##############
Also, I had other problems with the car. My HVAC controller was dead during the first 5 minutes of driving, then it would come on and be running fine until the next shutdown and restart. I had two spare controllers and both exhibited the problem...this stumped me....what were the odds of both being bad?
I also had a cold stumble at around 125* coolant temp from a first start overnight. Finally, my O2 sensor wires were chaffing and shorting against the heat shield. The sensor was replaced. The new PCM and ignition switch resolved problems as follows:
Diagnosis of HVAC?BCM
Intermittent failure of HVAC module and BCM controller showed that the ignition supply was compromised. Tested power supply and ground circuits and determined that there was no loss in continuity for any of them. Data stream revealed no communication with BCM as well. Tapping on the switch assembly revealed that there is a short internal to switch assembly. Completed test drive and noted that vehicle stumble was absent when computer switched to close loop and that the O2 sensors/fuel trims were reading correctly. No concerns are present at this time.
Cold stumble at closed loop
Work performed-investigate cause of trouble codes-O2 fault and MAP sensor fault. Back traced MAP sensor and found low reference for 5 volt circuit. Checked grounds and started back tracing to source. Tested PCM and found that the voltage regulation for the MAP sensor was not being interpreted by the computer correctly. When varying input voltage was provided, the PCM did not respond accordingly.
Yikes. Based on the issues you had, and the "fixes" by the shop.....it looks like they took you for a little ride. Sounds to me like you had chaffing O2 wiring, and a bad ignition switch.
09-25-2013, 06:59 PM
#11
Drifting
I think the pins for my Cooling fan 1 relay (45) got pushed down the relay now sits very loosly I am assuming I have to disassemble the box and fix those pins ?
09-26-2013, 04:01 AM
#12
Very interesting post.
I too have been experiencing intermittent HVAC power loss along with O2 sensor codes. I have a replacement ignition switch ready to install thinking that may be my issue. Your post gives me another possibility for the source of my problem.
I too have been experiencing intermittent HVAC power loss along with O2 sensor codes. I have a replacement ignition switch ready to install thinking that may be my issue. Your post gives me another possibility for the source of my problem.
09-26-2013, 06:51 PM
#13
Drifting
not to sound like a moron but I am having problems getting it seperated to appear like it does in pic 1 ... I took it out of the car , but cant get it seperated do I have to hammer out the 3 pieces? obviously not trying to break anything appreciate any input thanks !
05-08-2015, 09:41 PM
#14
Instructor
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Location: Louisville Kentucky
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Scared to drive it now.
Hello,
Your post is great. I have blown a 15AMP fuse twice now. The car will start, run, and then.. may start again but with very little power, won't run. I took it in and had the corvette folks look it over.. they could not find a thing. This all started after I had some cove lights put in.. I also have a plenum that lights up, but all this stuff goes directly into the battery. I don't know what to do, to be honest, I am afraid to even drive the car now. The car is a 2002 and has about 40, 000 miles on it.. Do you have any other suggestions for me? I'm afraid to drive it for fear it will just quit on the interstate. Thanks- Marilyn
Your post is great. I have blown a 15AMP fuse twice now. The car will start, run, and then.. may start again but with very little power, won't run. I took it in and had the corvette folks look it over.. they could not find a thing. This all started after I had some cove lights put in.. I also have a plenum that lights up, but all this stuff goes directly into the battery. I don't know what to do, to be honest, I am afraid to even drive the car now. The car is a 2002 and has about 40, 000 miles on it.. Do you have any other suggestions for me? I'm afraid to drive it for fear it will just quit on the interstate. Thanks- Marilyn
05-08-2015, 10:06 PM
#15
Le Mans Master
WOW... great pics and glad your up and running.
Did the GM Engineers have a conspiracy, and decide to make the MOST freaking complicated car on the planet? OMG...
Did the GM Engineers have a conspiracy, and decide to make the MOST freaking complicated car on the planet? OMG...
08-19-2016, 10:48 AM
#16
Racer
Member Since: Oct 2012
Location: Baltimore County, Maryland
Posts: 435
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I tried installing the hi four circuit from one of the vendors from the forum, no names. I pulled it out after it blew every fuse it was hooked too. Realized messing with the fuse box was a mistake so I tried to put it back the way it was. So what appears to be the case no is I have a high beam on the right side that works and on the left side it doesn't I really hope i didn't bend the pins in the fuse box. The issue concerns fuses 8,10,9,12. Any help would be appreciated.
08-19-2016, 11:43 AM
#17
"My Dad's a TV Repairman"
Relax- I've got you covered with the C5 abbreviated electrical schematic!
Last edited by Fed Up; 08-19-2016 at 11:43 AM.
08-19-2016, 12:16 PM
#19
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CI 6,7,8,9,11 Vet
St. Jude Donor '08
10-16-2023, 08:08 PM
#20
Ok, finally got around to this....had a couple requests to show what is inside....it ain't simple! A little background...I had a few electrical gremlins I could not figure out on my own, so I took the car in to a talented tuner near me. Long story short...rebuilt PCM, new ignition switch, and new fusebox, and a few other items, and I am back on the road and lovin' this car again. Keep in mind, I am no electrical wizard like some of the guys here, but I will try to explain a few things with the pictures.
Initial short was found here where the white paint shows one of the fuse locations we see when popping off the lid....
here is the backside and removable separator revealing the affected circuits...white paint again...
separator board removed....there is one on each side...notice all the fixed pins!
Now the fun begins....here is more of the internal stuff...
and now it is getting complicated to say the least....
All those extra little pins fell out from somewhere... What amazes me most is it looks like all that copper wiring is hand laid into the pin layout. I would shoot myself in the head before accepting a job like that Each one is carefully inserted into a notch, while avoiding touching any other conductor on that board....what a maze! What I did learn is all fuse boxes are interchangeable for the C5....they just need to carry the correct relays and fuses for your car depending on your options, etc. We put in a new 2004 box from Bowling Green's leftover stock from when the C5 production ended. The guy I bought it from purchased all the remaining C5 parts from the plant...12 semi loads of stuff! With a picture of my bad box taken earlier we duplicated the fuse/relay layout for my 97. It solved all my problems.
A little background...I had a few electrical gremlins I could not figure out on my own, so I took the car in to a talented tuner near me. Long story short...rebuilt PCM, new ignition switch, and new fusebox, and a few other items, and I am back on the road and lovin' this car again. Keep in mind, I am no electrical wizard like some of the guys here, but I will try to explain a few things with the pictures.Initial short was found here where the white paint shows one of the fuse locations we see when popping off the lid....
here is the backside and removable separator revealing the affected circuits...white paint again...
separator board removed....there is one on each side...notice all the fixed pins!
Now the fun begins....here is more of the internal stuff...
and now it is getting complicated to say the least....
All those extra little pins fell out from somewhere... What amazes me most is it looks like all that copper wiring is hand laid into the pin layout. I would shoot myself in the head before accepting a job like that
Each one is carefully inserted into a notch, while avoiding touching any other conductor on that board....what a maze! What I did learn is all fuse boxes are interchangeable for the C5....they just need to carry the correct relays and fuses for your car depending on your options, etc. We put in a new 2004 box from Bowling Green's leftover stock from when the C5 production ended. The guy I bought it from purchased all the remaining C5 parts from the plant...12 semi loads of stuff! With a picture of my bad box taken earlier we duplicated the fuse/relay layout for my 97. It solved all my problems.