Alternator voltage 16.5

[David Wakeman]

ok my 2016 mack pinnacle is going crazy running 16.5+ radio goes blank and guard dog will say my thing that holds you on a grade for 3 seconds after releasing break went blank what it's called sorry malfunction and transmission will not shift properly it will hold and whatever gear maybe 12th and I stop at a light I'll give it to gas or go to first second third fourth each and every gear the wires behind my master switch are too hot to hold I shut truck off shut master switch off for about 2 minutes start up and it goes fine both these drops down 15 something and it will do it randomly four to five times a day anybody got any kind of idea I keep thinking alternator but I'm not sure please help new guy on the Block

[mrsmackpaul]

Sounds like regulator isnt controlling the voltage

Dunno if it is built into the alternator or seperate

 

Paul

[Nickdieselz]

It sounds like your 2016 Mack Pinnacle is experiencing a serious electrical issue, likely related to voltage regulation or grounding problems. The symptoms you're describing—high voltage (16.5+ volts), electronic malfunctions (radio blanking out, hill assist malfunctioning, transmission shifting erratically), and overheated wires behind the master switch—are classic signs of an overcharging problem or a significant electrical fault. Here are some possibilities to investigate:

1. Alternator Overcharging (Regulator Issue)
   - Overvoltage: If your alternator is putting out 16.5+ volts, it’s overcharging the system. The normal charging voltage should be around 13.8 to 14.6 volts. Anything higher than that risks damaging sensitive electronic systems.
   - Voltage Regulator: Many trucks have an external voltage regulator, but some alternators have built-in regulators. If the regulator is faulty, it could be allowing the alternator to output excessive voltage.
   - Test the Alternator: Have the alternator and voltage regulator tested to ensure they are functioning correctly and not overcharging the battery or electrical system.

2. Battery Condition
   - Battery Health: If your battery is damaged or its internal resistance is too high, it can affect the overall electrical system and cause erratic voltage fluctuations.
   - Check Battery Terminals: Ensure the battery terminals are clean and tightly connected. Corrosion or loose connections can also cause voltage irregularities.

3. Grounding Issues
   - Bad Grounds: If the truck’s grounding system has corrosion or loose connections, it could cause intermittent power surges, voltage spikes, or erratic electrical behavior. A bad ground can make it seem like there’s an overcharging issue because power is not properly distributed or dissipated.
   - Check Ground Straps: Inspect all ground connections, especially the ones between the engine, frame, and body, for corrosion or damage. Tighten any loose connections and clean any corrosion.

4. Master Switch Wiring (Short or High Resistance)
   - Overheating Wires: The fact that the wires behind the master switch are getting too hot to touch suggests a short circuit or high resistance in that wiring. This could be drawing too much current and causing the electrical system to malfunction.
   - Check for Shorts: Inspect the wiring for signs of damage, fraying, or exposed wires that could be shorting out. Heat can also come from loose connections, so check the connections at the master switch for tightness.

5. ECM/GuardDog Electrical Interference
   - Electronic Malfunctions: Overcharging can cause electronic control modules (ECMs) to behave erratically. The GuardDog system and hill-hold assist may be malfunctioning because they aren’t receiving stable voltage.
   - Scan for Codes: Even though this might seem like a voltage issue, scanning for diagnostic trouble codes (DTCs) may give you clues about specific systems affected by the voltage spikes.

6. Transmission and Shifting Problems
   - Electronic Shift Control: The transmission relies heavily on stable voltage and clean electrical signals. If the voltage is too high or erratic, the transmission may not shift properly or could get stuck in a specific gear.
   - Inspect Transmission Wiring: Check for any damaged wiring related to the transmission control module (TCM), as voltage spikes can interfere with the shifting logic.

What You Can Do Next:
1. Test the Alternator: Use a voltmeter to check the alternator's output at the battery terminals while the engine is running. If the voltage consistently exceeds 14.6V, the alternator or voltage regulator is likely the issue.
2. Inspect Battery and Grounds: Check battery voltage with the engine off (should be around 12.6V) and with the engine running (should be around 14.0-14.6V). Also, verify that all ground straps and connections are clean and secure.
3. Check and Replace Master Switch Wiring: If the wires are overheating, you may have a short or high resistance. Carefully inspect the wires for any signs of damage and repair or replace them as necessary.

Fixing this issue soon is important to avoid further damage to your truck's electrical components. If you're unsure about testing the alternator or electrical systems yourself, it might be worth taking the truck to a professional mechanic or electrician specializing in heavy trucks.

Let me know how it goes or if you need further clarification on any of these points!