Electrical Issues - 1998 C5
Thread Starter
Heel & Toe
Joined: May 2015
Posts: 23
Likes: 3
From: Atlanta GA
Electrical Issues - 1998 C5
Hello,
I think my 1998 C5 is experiencing some electrical issues and I'm not quite sure what it is. The symptoms are;
Low Voltages:
At lights (with AC on), my voltages drop down to right about 13 volts (according to DIC and gauge), sometimes dropping below into the high 12's. The voltages will come up slightly at speed but usually they will hover around 13.4-.5
With AC off they seem to stay rather constant at 13.5 on the gauge but the DIC readout fluctuates from 12.9 to 13.7
Random dimming:
While driving and idle, the interior lights (radio, MPH/KPH light, etc) will dim and undim at a very high frequency (it's barely noticeable but I figure I would throw it in). However at idle, every few seconds the volts and the lights will dim noticeably. If I turn my turn signal on, the lights will dim quite noticeably with the turn signal.
Anyone have any ideas? Or am I just worrying about nothing?
Thanks,
I think my 1998 C5 is experiencing some electrical issues and I'm not quite sure what it is. The symptoms are;
Low Voltages:
At lights (with AC on), my voltages drop down to right about 13 volts (according to DIC and gauge), sometimes dropping below into the high 12's. The voltages will come up slightly at speed but usually they will hover around 13.4-.5
With AC off they seem to stay rather constant at 13.5 on the gauge but the DIC readout fluctuates from 12.9 to 13.7
Random dimming:
While driving and idle, the interior lights (radio, MPH/KPH light, etc) will dim and undim at a very high frequency (it's barely noticeable but I figure I would throw it in). However at idle, every few seconds the volts and the lights will dim noticeably. If I turn my turn signal on, the lights will dim quite noticeably with the turn signal.
Anyone have any ideas? Or am I just worrying about nothing?
Thanks,
Thread Starter
Heel & Toe
Joined: May 2015
Posts: 23
Likes: 3
From: Atlanta GA
Thanks for your post,
I just drove around a little bit. On my initial trip out to the store, the voltage read fine on the dash and stayed a strong 13.5-13.8V. After I left the store it was down to 13V in the dash. I fired up the multimeter when I got back and this is what I got:
13.88 MIN - 13.98 MAX coming out of the alternator
12.98 MIN - 13.5 MAX at the battery.
In car read a solid 13ish on the dial.
-Darkit
I just drove around a little bit. On my initial trip out to the store, the voltage read fine on the dash and stayed a strong 13.5-13.8V. After I left the store it was down to 13V in the dash. I fired up the multimeter when I got back and this is what I got:
13.88 MIN - 13.98 MAX coming out of the alternator
12.98 MIN - 13.5 MAX at the battery.
In car read a solid 13ish on the dial.
-Darkit
I would start at the alternator with a digital multi meter and measure the output voltage from the large wire on the back of the alternator to ground. It should be around 14 to 14.5 volts at idle.
I would then measure the voltage at the battery posts again while the car is idling. Should be within a tenth or so of the voltage measured at the alternator. If it is more than about 2 tenths of a volt less than at the alternator you MOST likely have loose or corroded connections at the starter. The alternator to starter wiring goes first to the post on the starter and loose or corroded connections are common on a C5.
The voltage that you see on the dash gauges is almost always significantly less than what you measure at the battery. This is because the gauges are downstream of the ignition switch and ignition switches on the C5 are a very problematic item with pitting and carbon buildup on the contact surfaces of the ignition switch.
FYI the thing on your dash that you put the key into is NOT the ignition switch. That is the ignition key cylinder and that turns the ignition switch which is behind the key cylinder.
Post back your results please.
I would then measure the voltage at the battery posts again while the car is idling. Should be within a tenth or so of the voltage measured at the alternator. If it is more than about 2 tenths of a volt less than at the alternator you MOST likely have loose or corroded connections at the starter. The alternator to starter wiring goes first to the post on the starter and loose or corroded connections are common on a C5.
The voltage that you see on the dash gauges is almost always significantly less than what you measure at the battery. This is because the gauges are downstream of the ignition switch and ignition switches on the C5 are a very problematic item with pitting and carbon buildup on the contact surfaces of the ignition switch.
FYI the thing on your dash that you put the key into is NOT the ignition switch. That is the ignition key cylinder and that turns the ignition switch which is behind the key cylinder.
Post back your results please.
Thread Starter
Heel & Toe
Joined: May 2015
Posts: 23
Likes: 3
From: Atlanta GA
Thanks for the reply,
I went for a drive this morning. First start up and going to the store, the gauge in the car read a solid 13.6-13.8 the whole way. After leaving the store however, it dipped to 13. After firing up the multimeter, this is what I got:
13.88 MIN to 13.98 MAX at the alternator.
12.90 MIN to 13.50 MAX at the battery.
(Usually was 13.5ish but dipped briefly every few seconds)
I measured the battery to be sure at it was good at 12.3
The dial gauge in dash was reading a constant 13.
-Darkit
I went for a drive this morning. First start up and going to the store, the gauge in the car read a solid 13.6-13.8 the whole way. After leaving the store however, it dipped to 13. After firing up the multimeter, this is what I got:
13.88 MIN to 13.98 MAX at the alternator.
12.90 MIN to 13.50 MAX at the battery.
(Usually was 13.5ish but dipped briefly every few seconds)
I measured the battery to be sure at it was good at 12.3
The dial gauge in dash was reading a constant 13.
-Darkit
I would start at the alternator with a digital multi meter and measure the output voltage from the large wire on the back of the alternator to ground. It should be around 14 to 14.5 volts at idle.
I would then measure the voltage at the battery posts again while the car is idling. Should be within a tenth or so of the voltage measured at the alternator. If it is more than about 2 tenths of a volt less than at the alternator you MOST likely have loose or corroded connections at the starter. The alternator to starter wiring goes first to the post on the starter and loose or corroded connections are common on a C5.
The voltage that you see on the dash gauges is almost always significantly less than what you measure at the battery. This is because the gauges are downstream of the ignition switch and ignition switches on the C5 are a very problematic item with pitting and carbon buildup on the contact surfaces of the ignition switch.
FYI the thing on your dash that you put the key into is NOT the ignition switch. That is the ignition key cylinder and that turns the ignition switch which is behind the key cylinder.
Post back your results please.
I would then measure the voltage at the battery posts again while the car is idling. Should be within a tenth or so of the voltage measured at the alternator. If it is more than about 2 tenths of a volt less than at the alternator you MOST likely have loose or corroded connections at the starter. The alternator to starter wiring goes first to the post on the starter and loose or corroded connections are common on a C5.
The voltage that you see on the dash gauges is almost always significantly less than what you measure at the battery. This is because the gauges are downstream of the ignition switch and ignition switches on the C5 are a very problematic item with pitting and carbon buildup on the contact surfaces of the ignition switch.
FYI the thing on your dash that you put the key into is NOT the ignition switch. That is the ignition key cylinder and that turns the ignition switch which is behind the key cylinder.
Post back your results please.
Melting Slicks
Joined: Jul 2004
Posts: 3,294
Likes: 480
From: Brea CA
Based on this info, you probably have a bad connection at the starter terminals. The charging wire from the alternator and the main battery cable are connected together at this point. It is a common failure point.
Best case is that the nut on the terminal is loose and has caused some arching. Clean the connections and re-tighten.
Worst case is the terminal is broken and the starter would need to be replaced.
Gary
Best case is that the nut on the terminal is loose and has caused some arching. Clean the connections and re-tighten.
Worst case is the terminal is broken and the starter would need to be replaced.
Gary
Drifting
Joined: Apr 2008
Posts: 1,510
Likes: 15
From: Ga
Change your battery.
Hello,
I think my 1998 C5 is experiencing some electrical issues and I'm not quite sure what it is. The symptoms are;
Low Voltages:
At lights (with AC on), my voltages drop down to right about 13 volts (according to DIC and gauge), sometimes dropping below into the high 12's. The voltages will come up slightly at speed but usually they will hover around 13.4-.5
With AC off they seem to stay rather constant at 13.5 on the gauge but the DIC readout fluctuates from 12.9 to 13.7
Random dimming:
While driving and idle, the interior lights (radio, MPH/KPH light, etc) will dim and undim at a very high frequency (it's barely noticeable but I figure I would throw it in). However at idle, every few seconds the volts and the lights will dim noticeably. If I turn my turn signal on, the lights will dim quite noticeably with the turn signal.
Anyone have any ideas? Or am I just worrying about nothing?
Thanks,
I think my 1998 C5 is experiencing some electrical issues and I'm not quite sure what it is. The symptoms are;
Low Voltages:
At lights (with AC on), my voltages drop down to right about 13 volts (according to DIC and gauge), sometimes dropping below into the high 12's. The voltages will come up slightly at speed but usually they will hover around 13.4-.5
With AC off they seem to stay rather constant at 13.5 on the gauge but the DIC readout fluctuates from 12.9 to 13.7
Random dimming:
While driving and idle, the interior lights (radio, MPH/KPH light, etc) will dim and undim at a very high frequency (it's barely noticeable but I figure I would throw it in). However at idle, every few seconds the volts and the lights will dim noticeably. If I turn my turn signal on, the lights will dim quite noticeably with the turn signal.
Anyone have any ideas? Or am I just worrying about nothing?
Thanks,
Thread Starter
Heel & Toe
Joined: May 2015
Posts: 23
Likes: 3
From: Atlanta GA
Thanks everyone for your help! 
Part of me was worried that this might be a PCM problem and I've heard on early C5's those are hard to find.
It's a new battery due to the old one leaking slightly, so I can't imagine it needing to be changed, but I'll get it checked anyway.
I'll check the wires and starter too. Should I consider maybe getting a new wiring harness if I have to replace the starter? Or is the harness tied into a bunch of other things that would cause me to open Pandora's box?
Thanks for the heads up!
-Darkit
Part of me was worried that this might be a PCM problem and I've heard on early C5's those are hard to find.
It's a new battery due to the old one leaking slightly, so I can't imagine it needing to be changed, but I'll get it checked anyway.
I'll check the wires and starter too. Should I consider maybe getting a new wiring harness if I have to replace the starter? Or is the harness tied into a bunch of other things that would cause me to open Pandora's box?
-Darkit
Le Mans Master
Joined: Feb 2012
Posts: 6,644
Likes: 479
From: OK
Thanks everyone for your help!
Part of me was worried that this might be a PCM problem and I've heard on early C5's those are hard to find.
It's a new battery due to the old one leaking slightly, so I can't imagine it needing to be changed, but I'll get it checked anyway.
I'll check the wires and starter too. Should I consider maybe getting a new wiring harness if I have to replace the starter? Or is the harness tied into a bunch of other things that would cause me to open Pandora's box?
Thanks for the heads up!
-Darkit
Part of me was worried that this might be a PCM problem and I've heard on early C5's those are hard to find.
It's a new battery due to the old one leaking slightly, so I can't imagine it needing to be changed, but I'll get it checked anyway.
I'll check the wires and starter too. Should I consider maybe getting a new wiring harness if I have to replace the starter? Or is the harness tied into a bunch of other things that would cause me to open Pandora's box?
Thanks for the heads up!
-Darkit
Why replace the starter? Your not having any issues it right? Even if the post is loose usually all you need to do is tighten it...
No disrespect intended, but it sounds like you have little or no experience... so, take a picture of the wiring on the starter BEFORE you mess with it so when you take off the wires (after disconnecting the battery) you get them back in the right spot (clean and tight)
http://www.popularmechanics.com/cars...a1454/4213127/
Last edited by 73Corvette; Jul 17, 2016 at 10:46 AM.
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