Winterizing Vehicles’ Electrical Systems
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MAINTENANCE
Find and correct deficiencies in your apparatus’ electrical system before it causes trouble and leaves you out in the cold.
photo by Mark R. Giller
Cold weather is quick to prey on the slightest weakness. As winter approaches in the cooler climates, fire department supervisors and apparatus operators will pay even more attention to their vehicles’ coolant levels, oil viscosities and the condition of their systems’ hoses and fittings. Smart operators know that electrical systems should merit this same kind of careful attention. Batteries should always be maintained at full charge. Even if a battery is new, it doesn’t necessarily mean it’s fully charged. Check it to be sure.
One of the main reasons for winterizing is to locate and correct weak links in the electrical system. Thickened oil, reduced battery power due to subfreezing temperatures and increased use of heaters, defrosters, and lights all contribute to increased electrical loads and demands for extra cranking power.
It’s important to take preventive measures before the snow flies.
Cranking motors, batteries, alternators, belts, switches, and electrical cables should be given a thorough inspection and testing each fall. For apparatus with 12-volt cranking systems, the need for testing is even greater because winter weather is harder on these systems than on 24-volt systems.
Here are several tips for winterizing electrical systems:
Cranking motors
Cranking motors are often overlooked during electrical system inspections due to their usually inconspicuous location. While it’s true that little maintenance is required on cranking motors, they’re highly susceptible to salt, dirt, and roads spray.
Check for corrosion, especially where it has “crawled” up a cable underneath the insulation. All electrical connections should be clean and tight, including where the motor is grounded to the frame and all connections at the solenoid field stud.
Also check the tightness of all mounting bolts and torque them to specifications if necessary.
Batteries
Batteries must be free of corrosion and foreign matter because a buildup of these contaminants can cause current leakage. In addition, be sure you maintain the proper electrolyte level. Clean and tighten battery post connections.
To check the specific gravity, or charge, of a conventional battery (a battery with one or more removable vent caps), test a sample of the electrolyte with a hydrometer. A reading of 1.260 indicates a fully charged battery; 1.230, a 75% charge; 1.200, a 50% charge; and 1.170, a 25% charge.
Maintenance-free (sealed) batteries must be checked using an accurate digital voltmeter that reads in hundredths of a volt.
Before proceeding, remove the battery’s “surface charge” by cranking— not starting—the engine for about 20 to 30 seconds.
A voltmeter reading of 12.60 volts signifies a fully charged battery; 12.45 volts, a 75% charge; 12.30 volts, a 50% charge; and 12.15 volts, a 25% charge.
Whether the battery is a vented conventional type or a maintenance-free type, a carbon pile load bank should be used to check its cranking capabilities. An ammeter and voltmeter are also necessary for this test. Using the manufacturer’s recommended load will determine the battery’s condition.
Check the charging voltage at each battery. Too high a voltage boils away the electrolyte, while too low a voltage prevents the battery from becoming fully charged. Large differences in voltage among batteries in 12/24-volt systems indicates defective connections or components in the dual-voltage system.
To change the charging voltage, adjust the alternator’s voltage regulator a little at a time until proper voltage and specific gravity are obtained.
If equipped with a series-parallel switch, make sure all electrical connections at the switch are clean and tight. This is extremely important because cranking current passes through this unit. Some vehicles have a solidstate transformer-rectifier instead of a series-parallel switch. Check these connections too.
If the vehicle will sit for long periods (such as during shop repair or if used as a spare), disconnect all batteries and trickle charge them from time to time. This offsets any discharge caused by alternator bleed current, self-discharge of the battery, and consequent sulfating (surface hardening of battery plates due to lack of charge in the battery).
Alternators
An “out of tune” alternator will certainly cause trouble in winter. Check the tightness of all mounting bolts and tighten to 50 foot-pounds if necessary. Also tighten the adjusting arm bolt to 50 foot-pounds. For best results, use SAE Grade 5 (or better) bolts and hardened washers. In addition, check the tightness and cleanliness of the terminal nuts.
Photo courtesy of Leece-Neville
Difficulty in turning the alternator shaft by hand could mean either bad bearings or some foreign matter is caught in the air space between the rotor and stator.
Check the current draw of the alternator system without the engine running. Normal bleed current is 0.01 to 0.1 amps. Bleed current in excess of this reading generally indicates that a positive rectifier is leaking and probably needs replacing.
One of the main reasons for winterizing is to locate and correct weak links in a vehicle’s electrical system.
Alternator belts
Using a tension gauge, check the strand tension on older belts, and after one hour of operation on new belts. If the tension is correct and belts “squeal,” or if belts appear worn or glazed, replace them with heavy-duty, oil-resistant belts. In multiple belt systems, replace all the belts as matched sets for best results.
Cables
Some specific electrical cables that should be inspected have been singled out, but all electrical system cables should be thoroughly checked for corrosion, cracks, or fraying.
All terminals must be securely soldered to their cables, and all connections must be clean and tight. Where cables bolt to the frame, areas around the bolt holes should be well-tinned with solder to insure clean, low-resistance connections.
Check for corrosion resulting from battery acid, road salt, etc., on a regular schedule. Again, pay particular attention to corrosion that has “crawled” up the cable underneath the insulation.
If in doubt about any cables, replace them. Those that are not visible (cables in harnesses or looms, for example) can be checked by running a series of voltage-drop tests.
As a final note, connect all wires and cables to their proper places. The regulator and/or alternator can be damaged if the battery is connected backwards, output leads are reversed, or jumper cables or battery charger leads are connected improperly. The motto “positive to positive and negative to negative” should be familiar to all vehicle operators.
Cold weather is particularly hard on our vehicles, and our electrical systems are extremely vulnerable to winter wear. This brief outline will serve as a guide for maintenance checks of all vehicles, no matter what the climate, even the vehicle that brings you to the fire station and home again.
