What is the correct battery voltage?

You need to check the alternator, which should provide an out put of 13.8V to 14.2V. There should be a voltage regulator on it which maintains the correct output voltage. This is likely to be faulty.
If you are getting too high a voltage then the voltage regulator is not working correctly.

that year 1986 alternator voltage regulator either external or internal follow alternator battery feed wire if you see battery feed wire going to black box mounted on fire wall you have external voltage regulator.if voltage regulator okay problem could be alternator fuse or fuse link could be faulty battery cables if cables over 20 years old but make sure alternator drive belt tension correct.

You need to check the voltage supply to the fuel gauge. If it is the same as the battery voltage the instrument voltage regulator has probably failed.

Instruments require a stable voltage that is substantially lower than battery voltage and this is provided by a small voltage regulator, usually found mounted on the printed circuit of the instrument panel.

Replace the voltmeter (voltage gauge).

The car can start up and run but the battery light is on, is this correct? if this is correct then have the alternator and battery tested, you may have a bad alternator or battery, most of the time the battery light turns on when battery voltage is less than 12 volts and the alternator is not charging the battery above 12 volts, test alternator, the car will die out if the alternator is not charging the battery, the engine will run until the voltage in the battery gets to low and then the car will start to do funny things, if the computers in your car do not have the correct voltage they will send false readings and make the engine run bad and shut down. good day.

This is where proper diagnosis comes in...as the TPS sensor voltage low because of a failed TPS sensor? Or was the TPS voltage low due to low battery voltage at the control module? Did you bother to check for the proper voltage at the TPS sensor connector before throwing parts at the problem? If the battery voltage goes low, it is NORMAL for the engine to not idle correctly. Low voltage at the control module can cause the computer to lose all of its "learned" data. It will have to "re-learn" how to idle the engine. This can sometimes take a few days. This is exactly WHY I keep telling people to not be disconnecting batteries in an attempt to "clear" computer fault codes.
If your battery has been going dead, you need to properly test and diagnose your battery and charging system. If this system is not working correctly, there is NO WAY your computer network can function correctly. - this MUST be diagnosed and repaired FIRST!

If you have a voltage meter, you should check if your voltage regulator is working correctly. The voltage regulator should keep the voltage to the battery something under 15 volts when the motor is running (more than 13.5 volts with all electrical turned off).

If more than 14.5 volts, you may be damaging your new battery and regulator is not working properly. Also, radio may not come on because a voltage sensor is protecting it from the high voltage. Antenna is controlled by radio so that should not be working either.

Good luck.

There's a TSB out for this concern. Its just a faulty relay

Printable View (8 KB) TSB
98-13-19

• ELECTRICAL - LOSS OF 4X4 SYSTEM
• LAMP - 4X4 LAMP ILLUMINATED
• LAMP - NO INTERIOR LIGHTING
• MOON ROOF - INTERMITTENT OR LOSS OF POWER
• REAR WIPER - INTERMITTENT OR LOSS OF POWER
• WINDOWS - INTERMITTENT OR LOSS OF POWER

Publication Date: JULY 6, 1998
LIGHT TRUCK: 1997-1998 EXPLORER, MOUNTAINEER
This TSB article is being republished in its entirety to correct the Service Procedure Steps. ISSUE: A flashing 4X4 lamp and/or a intermittent or loss of:

• Power windows
• Interior lights
• Rear wiper (if equipped)
• Moon roof (if equipped)
• 4x4 system (if equipped)

may occur on some vehicles. This may be caused by an intermittent Battery Saver, Accessory Delay or One-Touch-Down Relay operation and possible chafing of vehicle wire harness.
ACTION: Repair the affected circuit, and/or replace the Battery Saver, Accessory Delay, or One-Touch-Down Relay. Refer to the following Diagnostic/Service Procedure for details before replacing any components.
DIAGNOSTIC/SERVICE PROCEDURE Accurately RECORD ALL Diagnostic Trouble Codes (DTCs) from the Generic Electronic Module (GEM). The following codes can be generated by a faulty relay:

• B1371-Illuminated Entry Relay-Circuit
• B1302-Accessory Delay Relay-Circuit
• B1398-One-Touch-Down Relay-Circuit 1
• B1814-Rear Wiper Motor Down Relay-Circuit
• B1818-Rear Wiper Motor Up Relay-Circuit
• P1820-Transfer Case L2H Relay-Circuit
• P1824-Clutch Relay-Circuit
• P1828-Transfer Case H2L Relay-Circuit

DIAGNOSIS

1. If you have any of these codes B1371, B1814, B1818, and/or the interior lights or rear wipers are part of the customer concerns, go to Step 12. Otherwise locate the Accesory Delay Relay and proceed to next Step.
2. Put key in "RUN."
   1. If conditions are repeatable, go to Step 3.
   2. If conditions are not repeatable, follow standard GEM troubleshooting procedures.
3. Operate the windows until they fail then proceed to next Step.
4. Remove relay from relay box then proceed to next Step.
5. Check for battery voltage at Pin 87.
   1. If battery voltage is present, go to Step 6.
   2. If battery voltage is not present, go to Step 23.
6. Check for battery voltage at Pin 86.
   1. If battery voltage is present, go to Step 8.
   2. If battery voltage is not present, go to Step 7.
7. Locate the Battery Saver Relay and check Pin 3 for battery voltage.
   1. If battery voltage is present, go to Step 23.
   2. If battery voltage is not present, go to Step 16.
8. Return the Accessory Delay Relay back to the relay box then proceed to next Step.
9. Check for Ground at Pin 85.
   1. If Ground is present, go to Step 10.
   2. If Ground is not present, follow standard GEM troubleshooting procedures.
10. Check for battery voltage at Pin 30.
    1. If battery voltage is present, follow normal GEM diagnostic procedures.
    2. If battery voltage is not present, go to Step 11.
11. Check all female terminals at the relay.
    1. If all terminals are tight and all wiring crimps are good, REPLACE the Accessory Delay Relay, then go to Step 22.
    2. Make sure all terminals are tight and all wiring crimps are secure then go to Step 9.
12. Locate the Battery Saver Relay.
13. Put key in "RUN."
    1. If conditions are repeatable, go to Step 14.
    2. If conditions are not repeatable, follow standard GEM troubleshooting procedures.
14. Operate the windows until they fail then proceed to next Step.
15. Remove relay from relay box then proceed to next Step.
16. Check for battery voltage at Pin 1.
    1. If battery voltage is present, go to Step 17.
    2. If battery voltage is not present, go to Step 23.
17. Check for battery voltage at Pin 5.
    1. If battery voltage is present, go to Step 18.
    2. If battery voltage is not present, go to Step 23.
18. Return the Battery Saver Relay back to the relay box then proceed to next Step.
19. Check for Ground at Pin 2.
    1. If Ground is present, go to Step 20.
    2. If Ground is not present, follow standard GEM troubleshooting procedures.
20. Check for battery voltage at Pin 3.
    1. If battery voltage is present, follow standard GEM troubleshooting procedures.
    2. If battery voltage is not present, go to Step 21.
21. Check all female terminals at the relay.
    1. If all terminals are tight and all wiring crimps are good, REPLACE the Battery Saver Relay, then go to Step 22.
    2. Make sure all terminals are tight and all wiring crimps are secure then go to Step 19.
22. Verify all concerns are corrected.
    1. If all concerns are corrected, return vehicle to customer.
    2. If all concerns are NOT corrected, go to Step 23.
23. This is Not a GEM-related issue. Follow standard troubleshooting procedures.

PART NUMBER PART NAME F5TZ-14N089-B Relay - One-Touch-Down And Battery Saver FOAZ-14N089-A Relay - Accessory Delay F77Z-14B205-AA Generic Electronic Module (GEM) (1997 4X2) F77Z-14B205-BC Generic Electronic Module (GEM) (1997 4X4) F87Z-14B205-BA Generic Electronic Module (GEM) (1998 4X2) F87Z-14B205-CB Generic Electronic Module (GEM) (1998 4X4)
OTHER APPLICABLE ARTICLES: NONE
SUPERSEDES: 98-11-6
WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage
OPERATION DESCRIPTION TIME 981319A Perform Pinpoint Tests 1.0 Hr. 981319B Replace Relay 0.2 Hr.
DEALER CODING BASIC PART NO. CONDITION CODE 14B205, 14N089 42
OASIS CODES: 102000, 105000, 201100, 202000, 203200, 206000, 502000, 504000, 508000

Copyright © 1998 Ford Motor Company

your entire electrical system requires a minimum of 12.6 volts to operate correctly - if you don't have enough voltage then the system can react very unpredictably - check the voltage across the battery - if it is not 12.6 volts then charge or replace the battery to get the correct voltage - then start the vehicle and the voltage should increase to 13.5 to 15 volts - if the voltage does not increase, then the alternator is not charging and will need to have the electrical system serviced or the alternator replaced - good luck with your repairs

Battery light is a signal from the alternator that charge is below a given voltage , check charging system.