• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

Electrical Intermittent battery/charging issue

  • Thread starter Thread starter Grn92LX
  • Start date Start date May 7, 2023

Grn92LX

Fidanza Man!
Founding Member
Jan 14, 2001
6,819
64
129
New York
May 7, 2023
#1
  • May 7, 2023
  • #1
Other day was driving home and noticed my battery gauge (holley digital dash) reading just over 12v. Normally it reads around 14.4v. Made it home, put the battery back on the trickle charger and thought all was well. Drove the car around a few times since and no issues, battery gauge was showing 14.4v driving as usual. Took the car out yesterday all was fine but on the way home it happened again, battery was reading around 12.1v then by the time I got home it was reading just under 8v. I kept the car idling in the garage and verified with a meter and it was just under 8v.

Put the battery back on trickle charger, woke up and tested it today. Car off- 12.3v, car running battery 14.4v.

Any ideas? I tested power at the 3 harness connector and its got power at green/red wire and yellow wire. Tested from alternator post to ground and its fine too.

Battery is 4 years old and kept on a trickle charge when car is not in use. Wondering if it could be a bad cell or 2 in the battery? Gonna try and have it load tested at auto zone and see what happens.
 

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
27,849
10,530
203
polk county florida
May 7, 2023
#2
  • May 7, 2023
  • #2
My money is on the alternator.
That said, the constant charge input from a 'trickle' charger can cut a battery life short, a 'tender' or 'float' is what most would use to maintain battery life.
Just my opinion.
 

Grn92LX

Fidanza Man!
Founding Member
Jan 14, 2001
6,819
64
129
New York
May 7, 2023
#3
  • May 7, 2023
  • #3
Yes sorry worded it wrong. Its on a tender.
 
Reactions: General karthief

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
27,849
10,530
203
polk county florida
May 7, 2023
#4
  • May 7, 2023
  • #4
Grn92LX said:
Yes sorry worded it wrong. Its on a tender.
Click to expand...
I get it, I just have to mention it since I need to feel intelligent once in a while.
 

Grn92LX

Fidanza Man!
Founding Member
Jan 14, 2001
6,819
64
129
New York
May 7, 2023
#5
  • May 7, 2023
  • #5
Took it to the parts store to have them load test it. It failed so bought a new battery.
 
Reactions: limp

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
42,933
21,109
234
Box behind Walmart
May 7, 2023
#6
  • May 7, 2023
  • #6
That will likely fix the issue
 

FastDriver

I was uncomfortably high & wearing a helmet
SN Certified Technician
Sep 5, 2001
6,068
2,671
224
Vass, NC
May 9, 2023
#7
  • May 9, 2023
  • #7
I'm still concerned. Even when a battery is toast, an alternator should bring the system charge up to wherever the voltage regulator is set, as long as the alternator has the capacity to do so. So, getting down to 8V indicates a problem.

I still think you have a voltage regulator problem. That will trash a battery pretty fast, too.
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
42,933
21,109
234
Box behind Walmart
May 9, 2023
#8
  • May 9, 2023
  • #8
FastDriver said:
I'm still concerned. Even when a battery is toast, an alternator should bring the system charge up to wherever the voltage regulator is set, as long as the alternator has the capacity to do so. So, getting down to 8V indicates a problem.

I still think you have a voltage regulator problem. That will trash a battery pretty fast, too.
Click to expand...
My money is on a single battery cell that is/was shorting as it heats up.
 
Reactions: General karthief
I

Imatk

Active Member
Apr 17, 2005
101
10
29
Jun 28, 2023
#9
  • Jun 28, 2023
  • #9
If you've done anything to the gauge cluster lately, like replaced the speedo, check your PCB on the back of the cluster next to the lower connector.

If it's broken near that connector, your battery will not charge.
 
You must log in or register to reply here.

Similar threads

C
Stock 1993 charging issue at idle
  • Charlie1
  • Sep 21, 2025
  • Fox 5.0 Mustang Tech
Replies
7
Views
265
Fox 5.0 Mustang Tech Sep 24, 2025
Mustang5L5
K
Engine 2000 Mustang GT - Fuel issue post-blown spark plug repair
  • kenster1092
  • Feb 26, 2026
  • SN95 4.6L Mustang Tech
Replies
4
Views
290
SN95 4.6L Mustang Tech Mar 10, 2026
kenster1092
K
M
01 mustang 3.8 fuel pressure issue
  • Mhaley2006
  • May 29, 2026
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
0
Views
71
1996 - 2004 SN95 Mustang -General/Talk- May 29, 2026
Mhaley2006
M
I
98 Mustang GT dying
  • ItsMason
  • May 14, 2026
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
2
Views
70
1996 - 2004 SN95 Mustang -General/Talk- May 16, 2026
roblabsn95
R
A
Resolved Fuel Pump issue - test port jumped comes on (87 LX)
  • afjLX
  • Nov 16, 2024
  • Fox 5.0 Mustang Tech
  • 2
Replies
33
Views
2K
Fox 5.0 Mustang Tech Nov 26, 2024
afjLX
A
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?