Views:7 Author:Site Editor Publish Time: 2020-09-17 Origin:Site
A car or truck comes into your shop with a complaint of poor heater performance. The driver complains that on cold mornings the heater will blow cold during the drive to work in rush hour traffic. The car is not overheating and the air is coming from the correct ducts.
Your first reaction might be to install a new thermostat and inspect the heater core for a blockage. On the test drive, the system may perform great for you. Is the customer just cold blooded?
The issue could be the auxiliary water pump. This pump is not connected to the cooling of the engine. Its primary function is to circulate warm coolant to the heater core. If too little coolant is circulated, the blower fan will pull enough heat out of the coolant and cause the heater core to get cold.
These pumps were first used on luxury and diesel vehicles in the 1990s. Most diesel engines typically do not generate a lot of heat when running or idling. Coupled with the lower engine speeds, the coolant in the heater core would lose most of its heat before it passed through to the outlet. This would frequently cause drivers to complain about insufficient heating if they drove in stop-and-go traffic or cruised at speeds with lower RPM. So, adding an auxiliary coolant pump would provide enough volume of coolant to keep the heater core warm.
Engineers then started to use these pumps on gasoline-powered vehicles for the same purpose. This allowed vehicle designers to use larger heater cores to provide better passenger comfort.
The control of the pump as part of the automatic temperature control system keeps the cabin heated even after the driver has turned off the ignition. The system can keep the interior warm for short periods of time while the driver goes shopping or grabs a bite to eat.
These pumps will show up on more and more vehicles as engines become more efficient and generate less excess heat. Also, new technologies like hybrid drives and stop/start systems need auxiliary pumps to not only improve driver comfort, but also to keep the batteries at a constant temperature.