ACtion Magazine - July/August 2016 - (Page 31)

Freightliner M2 HVAC Control Testing and the internal control head logic. The desired position is considered to be reached when one of the following conditions is met: The actuator feedback position has been reached. The actuator is stalled for more than one second (that is, the feedback position does not change for more than one second). The target position corresponds to an end stop and one additional second extra drive in the same direction to seal the door against the case. The Temperature Selector Actuator Circuit Tests The motor drive circuit is checked with the key on engine off, blower motor on low speed. With the blend door (mix) actuator connector removed, measure the voltage across pins 5 and 6 of the actuator connector with a DMM. (Figure 8) While moving the temperature setting on the control head, a voltage of near battery voltage should be read. Next, check the actuator position sensor reference voltage circuit. Measure voltage be- tween pin 7 of the blend door actuator connector and the battery negative post. A 5-volt reading should be seen. Now measure the actuator position sensor reference ground circuit. Measure between pin 8 of the temperature blend door actuator connector and the battery positive post. The reading should be 12 volts. If any test fails, check the wiring between the control head and the actuator. If the wiring is good, replace the control head. Test the actuator position sensor feedback signal circuit. With all connectors connected, back probe pin B11 to B5 in the control head connector. The target voltage is 4.0 volts in the Full Hot Position. Move the temperature selector to the Full Cold Position. The target voltage is 0.5 volts. If any test fails, check the wiring between the control head and the actuator. If the wiring is good, replace the actuator. If all electrical tests pass, check for mechanical problems with the actuator and the blend door. Air Distribution (Mode) Actuator Circuit Tests The air distribution (mode) door actuator controls the direction the air is routed through the HVAC ducts in the cab. The mode door actuator is controlled by the air selection switch in the control head. (Figure 9) The control head senses the mode position by reading the feedback voltage from the actuator position sensor. The feedback voltage will be less than the 5-volt reference voltage sent by the control to the sensor. The target position is based on the mode selection switch setting and the internal con- You have enough on your mind, so let us take the worry out of your air conditioning needs. Global Parts Distributors is a full line, quality automotive air conditioning supplier. We can help streamline your inventory, suggest the right mix and take the worry out of having an A/C line. With seven warehouses across the country and a customer service team open from 7am to 8pm EST, we are here to service your needs. We make A/C simple for you. We are "your simple A/C solution" 1-800-722-5089 www.globalpartsdist.com Like us on Facebook / Follow us on Twitter twitter.com/globalpartsdist July/August 2016 * ACTION 31 http://www.globalpartsdist.com https://www.facebook.com/GlobalPartsDist https://www.twitter.com/globalpartsdist

Table of Contents for the Digital Edition of ACtion Magazine - July/August 2016

T/CCI's Wind Tunnel: Let's Test It
CAT Training @ T/CCI
Outlook
Service Port
Leonard's Law
Virtual View
Last Watch
By the numbers
Industry News
Association News
New Products

ACtion Magazine - July/August 2016