Q: I have a 2000 Ford F-150. Its A/C works perfectly, but the heater doesn't--all it does is blow out cold air. What could be the wrong? For each possible problem, what would the estimated cost of repair be?
A: When dealing with a no-heat condition, first check the coolant level. Even before an engine begins to overheat, the coolant level can be low enough to limit flow through the heater core. Also take a close look at the coolant-temperature gauge. A high or erratic reading may indicate air in the system or another coolant-system problem. A continuously low reading is a sign the thermostat is stuck open. This will prevent the engine from reaching normal operating temperature and, at the same time, limit or eliminate warm air at your feet. Some systems use a hot water valve to shut off coolant flow through the heater core during A/C operation. And poor coolant-system maintenance will eventually hamper heater performance by clogging up the heater core with grunge. On the dry side of the heat system are temperature-control components. Air-conditioning and heater-output temperatures are controlled by a door that blends the warm air from the heater core and the cool air from the air-conditioner's evaporator. The temperature knob on the control panel (or other means when dealing with a climate-control system) signals an electric-powered actuator (motor) to move the blend door to its proper position. There are too many possible causes to list with prices, but topping off the coolant is a cheap place to start.
Cadillac Conundrum
Q: When I tried to start my 2000 Escalade, it wouldn't turn over. Even though it cranks, I tried hooking up jumper cables. I also tried flooring the throttle in case it was flooded, but it still didn't start. There was no fuel smell (it had half a tank of gas) and no symptoms prior to this. My guess is it's the fuel pump, but I hope I'm wrong. Is there something else to check?
A: A technician would start on one of two diagnostic paths: (1) plug in a scan tool and check for trouble codes and obvious signs of incorrect data, or (2) do a quick check for spark at the spark plugs and fuel pressure from the fuel pump. If both look okay, he'd test for a good signal from the powertrain control module to the fuel injectors. (The PCM powers up the injectors so they can shoot fuel into the combustion chambers.) If nothing showed up by that point, he'd probably pull a spark plug or two to see if they were washed out by fuel, while keeping an eye out for any signs of internal engine damage. If there were a loss of spark and signal to the injectors, that might indicate a failure by a vital component such as the crankshaft position sensor. The crank sensor is what tells the system when the engine is rotating, and if so, how fast. Without that signal, there's nothing to trigger a spark or a fuel-injector pulse. Regarding the fuel pump: If there was little or no fuel pressure, you'd inspect the fuel regulator, filter, lines, and all applicable circuitry before condemning and replacing the pump. If it boils down to fuel-pump replacement, it's a good idea to mention Cadillac Technical Service Bulletin 04-06-04-088b to the technician doing the job. It describes an issue with a defective connector on top of the fuel-pump module, which is sunken into the fuel tank. This poor connection has caused repeat system failures, so the connector should be replaced with a modified unit, along with the fuel pump, on vehicles specifically listed in the bulletin.