Voltage gauge reads low when car's cold.
01-10-2019, 12:25 PM
#1
Rennlist Member
Thread Starter
Voltage gauge reads low when car's cold.
I've got a '99 996 that reads ~10V on the instrument cluster gauge when the car starts, but creeps up to about 13-13.5V over about 20 minutes as the car reaches normal operating temp.
I've confirmed with both a voltmeter (in the driveway) and the voltage display function on my radar detector (while driving) that the car goes to 14V as soon as I start it, and once hot, drops to somewhere between 13.0-13.5 and stays there all day... So the measurements at both at the battery and the cigarette lighter are normal. Car has no problems cranking and headlights don't seem weak... I know 13.0-13.5 is on the low side of normal, but a voltage regulator problem would look different than this.
It seems that only the reading on the voltmeter (and maybe the actual voltage) at the cluster that are low. This could presumably be a harness with a corroded connection or poor ground connection, or some inherit flaw in the cluster / measurement. I haven't troubleshot this any further than this yet, and am not real excited about tearing into the dash for something that's really just an annoyance.
I'm just doing step one of my research - read forums / consult the community! I was hoping someone had seen this before. Has anyone seen this before?
I've confirmed with both a voltmeter (in the driveway) and the voltage display function on my radar detector (while driving) that the car goes to 14V as soon as I start it, and once hot, drops to somewhere between 13.0-13.5 and stays there all day... So the measurements at both at the battery and the cigarette lighter are normal. Car has no problems cranking and headlights don't seem weak... I know 13.0-13.5 is on the low side of normal, but a voltage regulator problem would look different than this.
It seems that only the reading on the voltmeter (and maybe the actual voltage) at the cluster that are low. This could presumably be a harness with a corroded connection or poor ground connection, or some inherit flaw in the cluster / measurement. I haven't troubleshot this any further than this yet, and am not real excited about tearing into the dash for something that's really just an annoyance.
I'm just doing step one of my research - read forums / consult the community! I was hoping someone had seen this before. Has anyone seen this before?
01-10-2019, 02:54 PM
#2
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If the voltage is normal at the battery, and normal at the alternator, then it is probably your Y-cable. Check all connection points for corrosion and that they are tight, including the battery and engine ground straps.
#21 here http://www.autoatlanta.com/porsche-p...section=902-05
#21 here http://www.autoatlanta.com/porsche-p...section=902-05
01-11-2019, 03:13 PM
#3
Rennlist Member
It says 10V during the time you turn the key and that starter is working? That’s normal.
Or is shows 10V when you turn the key to the first position? A lot of cars show 11-11.5, 12. But you have to make sure everything is off on the car, because blower motors and accessories will pull it down.
It’s normal to see 14V after running and then dropping back down after awhile in the 13v-range.
Or is shows 10V when you turn the key to the first position? A lot of cars show 11-11.5, 12. But you have to make sure everything is off on the car, because blower motors and accessories will pull it down.
It’s normal to see 14V after running and then dropping back down after awhile in the 13v-range.
01-11-2019, 03:20 PM
#4
Captain Obvious
Super User
Super User
The gauge in the cluster isn't that accurate especially when the car gets old. Since the multi meter showed normal voltage, I wouldn't worry about it.
01-11-2019, 05:20 PM
#5
Curious to see your answers to Murphy's questions above and agree with Imo also.
Check the voltage on fuses A5 and B10 also. Those are the fuses that supply power to the instrument cluster. If you suspect the cluster, you can send it out to Modulemaster for inspection.
Check the voltage on fuses A5 and B10 also. Those are the fuses that supply power to the instrument cluster. If you suspect the cluster, you can send it out to Modulemaster for inspection.
01-23-2019, 01:12 AM
#6
Rennlist Member
Thread Starter
Thanks everyone for the replies and sorry about taking so long to get back on your advice.
Everything is normal:
1) The battery is 12.2 - 12.5 when the car's off (depending on how recently I drove it) and turning on the accessories drops that by a few 10ths in the driveway.
2) The battery shows a normal brief drop to 11V or something when starting but quickly goes to almost 14V indicating that the alternator & regulator are ok.
3) Voltages measured at the cigarette lighter inside the car are very close to the actual measurements at the battery. From this I believe that the y-cable and other stuff close to the battery is OK.
Except:
4) The gauge in the cluster reads more than 2V low while the car is running after a cold start, but slowly returns to a normal measurement over about 20 minutes as the car warms up.
My research indicates that the cigarette lighter is very close in the wiring harness/diagram to the cluster. The diagram shows that the lighter comes off what looks like a line out of the cluster at point 42. I don't know if this is a terminal, common branch in the harness, or a pin or connector number (I don't think it's a fuse)... the diagram isn't very clear. At any rate, there's not much between the two points, so I'm inclined to believe that my problem is in the cluster as proposed by Imo000.
It's more an annoyance than a problem, and has behaved predictably so far, and I'm inclined to leave it alone. The bushings on the front end need my love more than this problem does...!
I haven't checked A5 and B10 yet, but will try to get to that in the next day or two; that'll help conclude that it's the geriatric cluster.
Everything is normal:
1) The battery is 12.2 - 12.5 when the car's off (depending on how recently I drove it) and turning on the accessories drops that by a few 10ths in the driveway.
2) The battery shows a normal brief drop to 11V or something when starting but quickly goes to almost 14V indicating that the alternator & regulator are ok.
3) Voltages measured at the cigarette lighter inside the car are very close to the actual measurements at the battery. From this I believe that the y-cable and other stuff close to the battery is OK.
Except:
4) The gauge in the cluster reads more than 2V low while the car is running after a cold start, but slowly returns to a normal measurement over about 20 minutes as the car warms up.
My research indicates that the cigarette lighter is very close in the wiring harness/diagram to the cluster. The diagram shows that the lighter comes off what looks like a line out of the cluster at point 42. I don't know if this is a terminal, common branch in the harness, or a pin or connector number (I don't think it's a fuse)... the diagram isn't very clear. At any rate, there's not much between the two points, so I'm inclined to believe that my problem is in the cluster as proposed by Imo000.
It's more an annoyance than a problem, and has behaved predictably so far, and I'm inclined to leave it alone. The bushings on the front end need my love more than this problem does...!
I haven't checked A5 and B10 yet, but will try to get to that in the next day or two; that'll help conclude that it's the geriatric cluster.
10-28-2019, 10:58 PM
#7
Rennlist Member
Thread Starter
I'm reviving my dead thread here and have some mildly amusing notes about the source of my problem.
Are you ready for it...?
If I slap the dash above the voltage gauge, the needle pops up to an appropriate reading which matches a multimeter.
So, the gauge was sticking. That's it. That's all.
Are you ready for it...?
If I slap the dash above the voltage gauge, the needle pops up to an appropriate reading which matches a multimeter.
So, the gauge was sticking. That's it. That's all.
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Mike Murphy (10-28-2019)
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10-29-2019, 10:31 AM
#8
Captain Obvious
Super User
Super User
10-29-2019, 12:01 PM
#9
I'm reviving my dead thread here and have some mildly amusing notes about the source of my problem.
Are you ready for it...?
If I slap the dash above the voltage gauge, the needle pops up to an appropriate reading which matches a multimeter.
So, the gauge was sticking. That's it. That's all.
Are you ready for it...?
If I slap the dash above the voltage gauge, the needle pops up to an appropriate reading which matches a multimeter.
So, the gauge was sticking. That's it. That's all.
10-30-2019, 01:30 AM
#11
Race Car
Incidentally you can replace the volt gauge and oil pressure gauge out of the cluster - they are both individual components.
Not difficult to swap but but very tricky to get open
Not difficult to swap but but very tricky to get open
