Make electrical system service less challenging

Always buy and use the right tools and equipment

Remember, if you’re curious about a given tool or equipment application, please submit your question to PTEN so it can be considered in an upcoming Tool Q&A.

This month covers your questions regarding tools for electrical system work. Although onboard vehicle technology is progressing at a blazing pace, there are still many technicians that don’t have a good grasp on basic electrical fundamentals and troubleshooting. We can’t stress the importance of this enough, as tools and equipment alone won’t do the trick; you must understand the basics first. So, brush up on your skills by taking in a class or clinic to see how tools and techniques combine when tracking down electrical maladies.

Q: There’s been a lot of talk about Controller Area Network systems on later model cars. What do I need to service a CAN system?

A: You will need a scan tool with the right software or a PC with scan tool functionality to read codes from the CAN system and to interact with it. An older scan tool may need a software upgrade to be CAN-compliant. Make sure to check with the manufacturer of the scan tool hardware and software to determine their full capabilities. Some scan tool hardware/software combinations may be limited to displaying codes, but may not provide you with the capability to command circuits within the CAN system.

CAN systems were standard beginning with the 2008 model year, although you will also find this technology on some older models.

Q: What can I use to diagnose CAN-controlled lighting circuits?

A: Here, too, you will need a scan tool with the right software or a PC with the correct software for scan tool functionality. Once connected, you look for circuit fault codes and if needed, you can issue commands to the affected circuit on behalf of the body control module. It’s not like the old days of using a test light and simply swapping out bulbs when one doesn’t work.

Q: I’m seeing more cars with batteries marked VRLA or AGM on their case. It says not to use a conventional battery charger. What should I use?

A: Older battery chargers were designed for batteries with conventional, flooded, lead-acid construction. Newer batteries sometimes use an advanced design known as valve-regulated lead acid. A specific example would be an absorbed glass mat (AGM) type. To properly charge these newer types of batteries, you’ll need a charger with specific settings made to match the proper charge rate. Using the wrong type of charger, or the wrong charger setting, could damage one of these newer battery designs.

Q: The Volkswagen I’m performing brake service on has an electronic parking brake. In order to replace the disc brake pads, it says I have to retract the parking brake. What can I use for this?

A: You can control the parking brake either through a factory scan tool or a dedicated electronic parking brake service tool. Either tool allows you to command the parking brake as necessary for proper disc brake pad installation. Otherwise, you could damage the parking brake mechanism within the caliper. Electronic parking brakes can be found on various VW, Audi, BMW and Mercedes-Benz models.

Q: I’m trying to troubleshoot a circuit that keeps blowing fuses. I’ve inspected as much of the circuit as I can, but can’t seem to locate the fault. Problem is, as soon as I replace the fuse and start looking for the problem, the fuse blows again. Any ideas?

A: This is a perfect application for the use of a circuit-breaker-based circuit tester, along with an appropriate adapter for a given fuse type and location. You simply connect the circuit breaker in place of the fuse, and then begin testing the circuit for voltage and evident circuit problems. Since the breaker toggles on and off, it prevents excessive current flow that can result in a short-to-ground situation. Some circuit breakers for these types of testers also couple in a buzzer or tone generator, so that you know when the circuit is live and when the breaker opens.

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