Help with low voltage at Fuse post 2000 Trans Am
08-02-2017, 09:24 AM
#1
Help with low voltage at Fuse post 2000 Trans Am I'm frustrated to no end with this issue. I have a new battery, new battery cables, checked all the grounds in the engine bay and inside the passenger area. Grounds are all tight and secure so I'm pulling my hair out at this point. I have pulled the alternator and starter down too obviously when changing the cables so I double checked all of those connections. I read 12.4 volts at the battery but when I measure the voltage at the post by the fuse block it shows 1.3 volts. I can't understand how it can drop from 12 volts to that in only a few feet of new cable? What am I over looking or what should I look for? Stock cable setup and fuse block setup so nothing has changed there.
Symptoms are intermittent and all over the board. When it starts messing up all the dash instruments and inside lights blink or shut off completely. SOMETIMES I can turn the headlight switch and everything will come back to life. Has all the symptoms of a ground issue but I have checked every single ground that's posted here. Any ideas?
Thanks
Symptoms are intermittent and all over the board. When it starts messing up all the dash instruments and inside lights blink or shut off completely. SOMETIMES I can turn the headlight switch and everything will come back to life. Has all the symptoms of a ground issue but I have checked every single ground that's posted here. Any ideas?
Thanks
08-02-2017, 07:41 PM
#5
***UPDATE***
SO when I got home today the car was working again. 12 volts at the post....drove it around my neighborhood for about 20 minutes with no issues. Leave it and go grab some dinner with the wife and when I got back home it wasn't working again. Here is the progress I have made so far.
I do have 12 volts getting to the post but when the cable is attached to the post the current has a break somewhere and that is why I was getting a low voltage reading when I used the closest ground. When I check straight from the battery to the cable end that goes over the post I have my 12 volts. So tomorrow I guess I will be following the wires in the fuse box assembly to see whats going on. I've thought about changing all of my relays because its acting like one would act when wearing out. I have swapped them around but with my luck they could all be bad.
Is there anywhere in the circuit I should check? Where is the main ground for the fuse block?
SO when I got home today the car was working again. 12 volts at the post....drove it around my neighborhood for about 20 minutes with no issues. Leave it and go grab some dinner with the wife and when I got back home it wasn't working again. Here is the progress I have made so far.
I do have 12 volts getting to the post but when the cable is attached to the post the current has a break somewhere and that is why I was getting a low voltage reading when I used the closest ground. When I check straight from the battery to the cable end that goes over the post I have my 12 volts. So tomorrow I guess I will be following the wires in the fuse box assembly to see whats going on. I've thought about changing all of my relays because its acting like one would act when wearing out. I have swapped them around but with my luck they could all be bad.
Is there anywhere in the circuit I should check? Where is the main ground for the fuse block?
08-02-2017, 10:24 PM
#6
TECH Fanatic
Does that cable feel hot or warm to the touch? If that cable were dropping 11.4 it would be so hot I'm sure it would melt the insulation and be very hot ... not to mention what it would do to the battery.
08-02-2017, 10:38 PM
#7
When your checking for voltage, I would connect the black lead of the meter to the negative terminal of the battery and the red lead of the meter to the stud at the fuse block. If your not consistently getting a 12V reading, I would check continuity of the wire between the battery and fuse block while moving it around to check for a loose connection or possibly a broken wire.
Last edited by peterpar; 08-03-2017 at 09:50 AM.
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08-03-2017, 05:09 AM
#8
Thanks for the schematic, that will help me a lot! The cable from the battery that goes to the post is good so I have to trace from there. This afternoon I am just going to start tracing the current. Funny that the cruise control is a main ground because a few years ago I had to replace it, it was throwing the electronics off then but I forgot those symptoms. I will just unplug it and eliminate that from causing an issue for now. I'll report back later hopefully with some good news.
One last question, where is the BCM? I've read many posts about that going bad and screwing up a lot of systems.
One last question, where is the BCM? I've read many posts about that going bad and screwing up a lot of systems.
08-03-2017, 08:08 AM
#9
You aren't just assuming that the cable from battery to fuse box is good because it's new? You've actually tested it? The symptoms you describe (12V at one end of cable, 1 volt at other end of cable) can only be attributed to a bad cable or improper measuring. Nothing beyond the fuse block end of the cable (relays, grounds, etc.) would have any impact at all.
08-03-2017, 08:15 AM
#10
No in my update I addressed that but basically yes I have 12 volts coming through the cable completely I found out last night after testing it against the battery. The issue then becomes when I hook the 12 volts up to the fuse box terminal (bolt) and then check the voltage from there to the ground on the shock terminal or the grounds on the brace in front of the radiator, I get anywhere from 1-6 volts. So basically something is not transferring through the fuse box to the systems.
08-03-2017, 10:20 AM
#11
I just noticed the schematic I posted above didn't have the fuse block drawings I intended to include. I deleted the link above and added the updated file to this post. If you have 12V power at the stud, you should be able to pull fuses in the blocks one at a time and find 12V to one of two the terminals of the fuse. If not, trace back to stud.
Something else I would suggest is to used the same ground point when checking for voltage. It will eliminate one less variable.
Something else I would suggest is to used the same ground point when checking for voltage. It will eliminate one less variable.
08-03-2017, 11:38 AM
#12
No in my update I addressed that but basically yes I have 12 volts coming through the cable completely I found out last night after testing it against the battery. The issue then becomes when I hook the 12 volts up to the fuse box terminal (bolt) and then check the voltage from there to the ground on the shock terminal or the grounds on the brace in front of the radiator, I get anywhere from 1-6 volts. So basically something is not transferring through the fuse box to the systems.
Remove the ground bolts on the radiator support, sand the metal where the wires sit under the bolt, and make sure those tiny terminals get cleaned with sand paper too
08-03-2017, 12:11 PM
#14
I just noticed the schematic I posted above didn't have the fuse block drawings I intended to include. I deleted the link above and added the updated file to this post. If you have 12V power at the stud, you should be able to pull fuses in the blocks one at a time and find 12V to one of two the terminals of the fuse. If not, trace back to stud.
Something else I would suggest is to used the same ground point when checking for voltage. It will eliminate one less variable.
Something else I would suggest is to used the same ground point when checking for voltage. It will eliminate one less variable.
Chrysler kid, I did remove those bolts and the one on the shock tower directly above the fuse box assembly to burnish the metal and remove any corrosion/paint that could possibly block the grounding. I appreciate the input though because I didn't think of that until yesterday and I've been trouble shooting for a while now.
Thanks for all the input fella's, I hope I can report back later what it was.
08-03-2017, 12:33 PM
#15
Let me add to this point, I would start checking for voltage using the negative battery post as the ground source for the meter. This is the ground source for all grounding points on the car. If you get a 12v reading doing this, but are still having problems, change the meter ground point to where the negative battery cable attaches to the right wheel well. Not getting the same 12V reading between these two points should be indication of a bad cable or connection. You said you replaced the cables, did that include the negative cable too.
08-03-2017, 12:46 PM
#16
Yes I replaced the positive and negative cables. I started using the negative post at the battery because for some reason when I tried using the ground on the shock tower it was not at 12 volts, it was 6.1 yesterday afternoon.
With my luck the problem won't be there when I get home and I'll have to crank it, drive it..etc to recreate the problem. Its very intermittent.
With my luck the problem won't be there when I get home and I'll have to crank it, drive it..etc to recreate the problem. Its very intermittent.
08-03-2017, 06:58 PM
#17
***Update***
When I got home the car was fine until I drove it around the block. The gauges started flickering again so I went home, shut the car off and then the problem was back. I turned the light switch and it came back to life. I then decided to unplug the cruise control to eliminate that because in the past it was an issue. After that I drove around the block for a good 20 minutes, back home then on the road for a few miles to return. Not sure if the problem just hasn't reared its ugly head again or not but I have another problem. Every time I crank the car the computer resets now. With the big cam that's a big problem because relearned the cam every time is not going to work obviously. SO what now? What could cause the computer to reset?
When I got home the car was fine until I drove it around the block. The gauges started flickering again so I went home, shut the car off and then the problem was back. I turned the light switch and it came back to life. I then decided to unplug the cruise control to eliminate that because in the past it was an issue. After that I drove around the block for a good 20 minutes, back home then on the road for a few miles to return. Not sure if the problem just hasn't reared its ugly head again or not but I have another problem. Every time I crank the car the computer resets now. With the big cam that's a big problem because relearned the cam every time is not going to work obviously. SO what now? What could cause the computer to reset?
08-03-2017, 10:35 PM
#18
If the computer has to relearn itself, I would think that it had to lose its power supply. Whether it lost the 12V supply or the ground I don't know. The fact that you mention the gages start to flicker makes me think it could be a ground issue. I noticed you saying you installed a cam at some point. That would tell me you had the heads off. Ground G110 is locate on the rear of the left head and it provides a ground to the PCM, cruise control and gages, all things that you have listed as effected. Is it possible this ground could be loose?
Last edited by peterpar; 08-03-2017 at 11:18 PM.
08-04-2017, 04:17 AM
#19
If the computer has to relearn itself, I would think that it had to lose its power supply. Whether it lost the 12V supply or the ground I don't know. The fact that you mention the gages start to flicker makes me think it could be a ground issue. I noticed you saying you installed a cam at some point. That would tell me you had the heads off. Ground G110 is locate on the rear of the left head and it provides a ground to the PCM, cruise control and gages, all things that you have listed as effected. Is it possible this ground could be loose?
08-04-2017, 03:43 PM
#20
I replaced the ignition relay today and left the traction control unplugged. Drove it to the gym and back with no issues. I plan on driving it more over the weekend to see if it rears its ugly head again but at least its not shutting down now. I am starting to think the cruise control is the culprit.