CAN highlights


From MACS Technical Think tank

Controller area networks may be the new standard, but even they have three different levels, or speeds, at which they operate. CAN C is the high speed network, able to transmit data at over 500Kbps. Compare that to older systems, like UART, that transmitted at only 8Kbps. CAN C is typically used for vehicle critical systems like the ECM, ABS and VSC – systems that need information now!
CAN B is medium speed network, operating at speeds of 83Kbps, and is used for semi-critical vehicle systems. CAN A operates at the lowest speed, roughly 10Kbps, and is used for convenience systems, like entertainment and HVAC.
CAN uses a dual-wire bus, with each module wired to it in parallel. Unlike older systems, there is no master module. Each module has equal access to the bus and supplies its own power to the network. Messages sent along the bus are seen by all modules, but only those needed for an individual module’s operation are recognized and acted on.

The failure of one module will not necessarily stop all communication between modules. By going to the diagnostic link connector (DLC), you can quickly check the bus itself for opens or wiring faults by measuring the resistance between pins 6 and 14. A reading of 60 ohms indicates the bus itself is intact.

In diagnosing the system, keep in mind that if a module has dropped off the bus, you may not see it on your scan tool when you look for it – it’s as if the module doesn’t exist. Be sure to check the computer data lines schematic to identify all the modules you should be able to communicate with.

When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.

If you’re a service professional and not a MACS member yet, you should be, click here for more information.

You can E-mail us at macsworldwide@macsw.org or visit http://bit.ly/cf7az8 to find a Mobile Air Conditioning Society member repair shop in your area. Visit http://bit.ly/9FxwTh to find out more about your car’s mobile A/C and engine cooling system.

The 32nd annual Mobile Air Conditioning Society (MACS) Worldwide Convention and Trade Show will take place January 18-20, 2012 at the Rio All Suite Hotel and Casino in Las Vegas, NV.

Advertisements

About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues. www.macsw.org
This entry was posted in Automotive, Automotive training, Mobile Air Conditioning and tagged , , , , , , , , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s