 another stupid electrical question, what is right/normal/bad |
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| timofly |
 Nov 24 2011, 11:11 AM
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#1
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Member  Group: Members Posts: 168 Joined: 21-February 09 From: VA Member No.: 10,082 Region Association: MidAtlantic Region  |
74 2.0 FI with console voltage gauge, shows 13+ volts running with no lights on. Turning on parking lights or stepping on the brake drops it to about 12.2. Turning on headlights drops it further to just below 12. Fog lights have no effect (they are working) but turn signals will drop it to 11 with headlights on. Brakes with headlights on also drops it to 11 volts. Battery (Red Top) shows 12.5 volts with engine off after a good run.
Before someone says: "Did you read the threads here on this?" Yes, I have, and the same conditions draw responses ranging from "that's normal" to "your regulator/aternator/phisoginator is about to fail", so they leave me right where I started. I have cleaned the grounds in the front fenders right by the headlight motors, with no effect. So, three dumb questions: 1. what's the best way to check the voltage being sent to the battery 2. where is the ground connection to the body for the tailights, 3. am I worrying about nothing? Happy Thanksgiving to all and thanks for any advice. |
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| Mike Bellis |
Nov 24 2011, 11:21 AM
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#2
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Resident Electrician Group: Members Posts: 8,347 Joined: 22-June 09 From: Midlothian TX Member No.: 10,496 Region Association: None 
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Check the actuall battery voltage at the battery.
The tail light ground is on the side wall below the relay board. The stock voltage gauge is almost useless. |
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| ArtechnikA |
Nov 24 2011, 11:26 AM
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#3
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
QUOTE(timofly @ Nov 24 2011, 12:11 PM)  74 2.0 FI with console voltage gauge, ... The console gauge is, like horoscopes and 911 oil level gauges, 'for entertainment purposes only.' QUOTE 1. what's the best way to check the voltage being sent to the battery At the battery posts. QUOTE 2. where is the ground connection to the body for the tailights, can't help you on that one, sorry... QUOTE 3. am I worrying about nothing? Probably. Where the console voltmeter connects, it cannot be reliable, except when it shows '0' with the ignition off... |
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| timofly |
Nov 24 2011, 11:26 AM
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#4
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Member Group: Members Posts: 168 Joined: 21-February 09 From: VA Member No.: 10,082 Region Association: MidAtlantic Region |
QUOTE(kg6dxn @ Nov 24 2011, 12:21 PM) Check the actuall battery voltage at the battery. The tail light ground is on the side wall below the relay board. The stock voltage gauge is almost useless. I should have clarified that the battery voltage of 12.5 was measured at the battery, not taken from the gauge. |
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| Tom |
Nov 24 2011, 11:32 AM
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#5
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Advanced Member Group: Members Posts: 2,139 Joined: 21-August 05 From: Port Orchard, WA 98367 Member No.: 4,626 Region Association: None |
This is caused by where the voltage reading is being taken. Off the harness from fuse S9 after the power is being applied to other loads.
Best place to monitor battery voltage is directly from the battery. It is normal for this to happen on the 914 due to the place where the voltage is monitored, the voltage at S9, not the battery. Lots of "line loss/ IR drop" involved. If they had used larger wires, it wouldn't be so evident either. Tom |
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| Mike Bellis |
Nov 24 2011, 11:38 AM
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#6
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Resident Electrician Group: Members Posts: 8,347 Joined: 22-June 09 From: Midlothian TX Member No.: 10,496 Region Association: None
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QUOTE(timofly @ Nov 24 2011, 10:26 AM) QUOTE(kg6dxn @ Nov 24 2011, 12:21 PM) Check the actuall battery voltage at the battery. The tail light ground is on the side wall below the relay board. The stock voltage gauge is almost useless. I should have clarified that the battery voltage of 12.5 was measured at the battery, not taken from the gauge. Each cell of the battery is about 2.1 volts. A car battery has 6 cells. Your voltage at 12.5V is acceptable. Most alternators/regulators do not produce charging voltage below 1500rpm. At idle with all your loads turned on, you should see less than 12.5V. At >2000rpm you should see about 13.5-14.5V at the battery. The stock volt gauge is wired to see all the loads in the car. That's why you can turn on the blinkers and watch it bounce. If you want the stock gauge to be more "accurate", you would need dedicated power and ground wires from the battery 12gauge or larger. |
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| underthetire |
Nov 24 2011, 11:51 AM
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#7
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914 Guru Group: Members Posts: 5,062 Joined: 7-October 08 From: Brentwood Member No.: 9,623 Region Association: Northern California |
At 12.5 volts at idle with everything on, yer fine. Best use I found for the stock gauge is to verify the brake lights and turn signals are working. No needle movement, and you have a failure!
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| 76-914 |
Nov 25 2011, 12:04 PM
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#8
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,700 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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I use mine to remind me that I've left the turn signal on, again. (IMG:style_emoticons/default/headbang.gif)
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| windforfun |
Nov 25 2011, 06:05 PM
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#9
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Advanced Member Group: Members Posts: 2,054 Joined: 17-December 07 From: Blackhawk, CA Member No.: 8,476 Region Association: None
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Don't let your old voltage regulator fail & boil your battery.
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