Question: Is it possible that my alternator is putting out enough charge that my truck will start on warmer days and be completely dead on cooler days? It's a 2WD V-6/automatic Ford Ranger. I replaced the battery cables to the battery and bought a new battery. On cold mornings, I have to jump start it.
Answer: Cold temperatures will have an adverse effect on a weak battery, but typically not on an alternator. You have to test the system completely with the proper equipment to find the cause of the problem. Load test the battery, even though it's new. Test the charging system (14.2 volts and specified amperage output). Amperage draw test to be sure the starter is not drawing too much current; if all lights are dim or off, it's not the starter. Check all battery and charging system connections. Check for excessive parasitic draw, such as a trunk light staying on when it shouldn't be. This requires a test light or ammeter connected in series with the battery--30 milliamps max. It shouldn't be a tough one to figure out after running the standard battery of tests.
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at email@example.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.
Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage — visit Alex Steele at www.RealWorldAutomotive.com.