Ford's Heater Core Shut-Off Valves (HCSO) From Ford Service Manual: The engine cooling system may contain multiple control valves for improving fluid warm-up rates of both the engine and transmission. These valves are PCM controlled and primarily used for thermal control of engine metal and transmission fluid temperatures by diverting engine coolant to the appropriate component. These digital outputs include an engine coolant bypass valve (CBV), a heater core shut-off valve (HCSO), an active transmission heating valve (ATWU-H), and an active transmission cooling valve (ATWU-C). More and more HVAC systems are bringing back the heater valve and this time the evolution of technology has resulted in electronic module controlled solenoids doing the job of blocking or allowing the flow of hot coolant into the heater core. (Figure 3) Dave Hobbs The Coolant Bypass Valve is normally closed (de-energized) forcing all of the engine coolant through the radiator to provide maximum "cooling" of the engine and components when the thermostat is open. When opened, a portion of the engine coolant bypasses the radiator providing for coolant pressure and flow control. The Heater Core Shut Off valve has a single purpose which is to limit coolant flow for fast engine warm-up. The ATWUC valve will transfer engine coolant from the sub-radiator to the Transmission Oil Cooler (TOC) when energized, resulting in a heat transfer from the transmission into the engine coolant (over-temperature control of the transmission). The ATWU-H valve is used to provide hot engine coolant to the TOC to improve transmission fluid temperature control. ■ Figure 3: This Ford Escape's solenoid style heater valve essentially works the same as its vacuum and cable actuated predecessors. The solenoid is activated to close off the flow of hot coolant to the heater core so the evaporator can function more effectively thanks to the hot coolant no longer being circulated into the heater core. BATTERY POWER LOSSES & ELECTRONIC MODULES So you disconnected the battery to perform an R&R on something HVAC related? Sold your customer a new 12-volt battery along with that HVAC job? No big deal, right? Just reset the clock in the radio right? Although many vehicles today this still applies to, many techs are finding out it can be a big deal unless you perform resets and relearns on various components on the vehicle. One driving factor for requiring new battery registration is the increasing popularity of 12-volt 'Start/Stop' systems and vehicles with smart charging and battery management. In the chart shown in figure 4 are a few applications along with a few operations that need to be performed whenever the battery power is lost to the vehicle. Those procedures are always the easiest to find but one tip we'll pass along is to simply look up "battery replacement." Often accompanying the information related to new battery registration (typical for many European vehicles today) are just Figures 4: This chart illustrates just a few of the complications of battery power resets. Whenever a loss of battery power has either occurred or is anticipated in the repair process, it is important to research the procedures for relearns and resets for that vehicle in the service manual and perform those procedures before returning the vehicle to the customer. Also, new batteries may need to be 'registered' in the vehicle they are being installed in for the charging system to know a new battery charge rate is now required. Failure to register a new battery to a vehicle requiring this procedure may result in a new 12-volt battery that fails in a few months! September 2017 2 MACS Service Reports