The next step is to perform a cranking voltage test. Unlike a carbon pile load test, this test only applies a load to the battery for a few seconds. With your DMM still connected, turn on the meter’s record (or MIN/MAX) feature and crank the engine. Repeat the process three times, allowing the engine to run for a few extra seconds on the last cycle before turning it off. Your minimum reading should be above 10.0 volts (as opposed to the 9.5 volts for a 15-second carbon pile load test). Anything less than 10.0 volts indicates a battery that has reduced capacity.
The best way to check the coolant mixture ratio is with a refractometer. Coolant test strips rank No. 2.
But before you recommend a replacement, be sure to consider the battery’s temperature when you tested it. If it didn’t meet 10.0 volts while it was still in the 70s, you are certainly doing your customer a favor when you recommend a new one before the weather drops to the 20s.
Now check your meter’s MAX recording. This is charging system voltage and should fall between 13.5-15.0 volts. Refer to the OEM service specifications for your specific vehicle, as some cars use intelligent charging strategies that initially charge at a higher rate than you may be used to seeing.
The last test is the battery recharge current test. This is where you’ll need an accurate amp clamp. When the engine is started, the battery is temporarily depleted. As soon as the engine begins to run, the alternator comes on line to replenish what was lost. Initially, the NET current (the total difference between system demand and alternator output) flowing into the battery can be substantial but it should only take a few minutes (allow five) for a good battery to recover. The NET current flow then should drop to less than 10 amps (some sources say 3 amps). The lower the number, the better it is for the health of the generator. If the number remains high (caused by an internal fault in the battery, typically sulfation), the generator can overheat and fail. (OK, now you know why Mr. Johnson has had four different alternators in the last three months).
Coolants provide important protection for the engine and, on hybrids, for the high voltage electrical systems. Well, the water does most of the cooling. The coolant is added to the water to enhance both boil-over and freeze points. In addition, inhibitors in the coolant protect system components from corrosion and erosion. With all the important work coolant has to do, don’t rely on a simple visual check of the coolant bottle’s fluid level alone.
Coolant test strips can be used to test coolant mixture and acidity; the two key factors you need to determine whether or not the system requires service.
We can, though, start there. Check both the level and condition of the coolant in the reservoir. Low levels happen for one reason only: leakage. So if the level is low, be sure to determine why it’s low and correct the problem. Low coolant levels promote air in the system and coolant can’t protect what it can’t touch. Debris in the tank, too, can only come from one place and is evidence of a cooling system that has received less attention than it should have.
Next, check the water/coolant mix with (in order of preference, best to worst) a refractometer, test strip or gauge-style hydrometer. No ball-type hydrometers please and take your sample from the system and not the reservoir. A coolant mix in the 40 to 60 percent range is considered acceptable. Follow up that check with a check of the pH, or acidity, of the coolant. The pH is an indication of the health of the inhibitors. Typically, the coolant will become more acidic as the inhibitors drop out. If the coolant passes this test as well, your customer’s coolant should be ready for the winter ahead. On the other hand, if the coolant is too acidic (or too alkaline), a coolant flush and refill with fresh coolant is needed to insure system protection.