I’m stuck with no heat during the winter time. What’s going on?

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We get this question quite often, especially during the winter months. We know that getting stuck with no hot air can sometimes be as bad as being stuck with no cold air. It’s actually quite a common problem on the earlier S-Types from 1999-2002. These models use a 5-port DCCV (Dual Climate Control Valve) (a.k.a. “heater valve”) that tend to get stuck in closed position. The 3-port DCCVs from the 2003-2008 S-Types don’t tend to get this problem. If your climate control system doesn’t blow any hot air, here is how you diagnose this problem:

Step 1 – Check your coolant levels
Pop open the hood. Take a look at the coolant expansion tank. Open the pressure cap carefully (warning: hot coolant is under pressure and can burn you!), or wait for things to cool down first. Check the coolant level inside. Check the cleanliness of the coolant. These expansion tanks are prone to crack after years of service. Check for leaks around the tank. Check for leaks around the hoses and radiator. If all looks good, move on to the next step.

Step 2 – Bleed your cooling system
Over time, pockets of air (“bubbles”) may form inside your cooling system. After coolant is drained and refilled, the system must be bled properly to eliminate these air pockets. Having excess amounts of air pockets reduces the cooling system’s ability to keep the engine cool. It may also impair your climate control’s heating function. The bleeding procedure varies between the different years and engine options. Here is the procedure for a 2000 S-Type with 3.0L V6 engine:
- Install the expansion tank cap.
- Leave heater air bleed open.
- Start the engine and set the heater to 29 C / 90 F [both driver and passenger controls].
- Close heater air bleed when a steady stream of coolant flows during engine idle.
- Allow the engine to idle for 5 minutes, adding coolant the expansion tank to maintain the COLD FILL MAX level.
- Open the heater air bleed to release any trapped air, close the heater air bleed.
- Increase the engine speed to 1500 rpm for between three and five minutes or until the heater is blowing hot air.
- Return to idle and verify that heater is blowing hot air.
- Turn off engine and allow to cool.
- Top off coolant to COLD FILL MAX.
If bleeding the system didn’t eliminate the symptom of “no hot air,” then move on to Step 3.

Step 3 – Check your DCCV (heater valve)
Whether you have a 5-port (1999-2002) or 3-port (2003-2008) heater valve, it is prone to corrosion and leakage. If you have a 5-port valve, and it looks clean from the outside, then there is a good chance it is blocked off internally. The best way to check this is to remove the heater valve, then try to force air or water through the ports manually. You can even try blowing through it with your mouth (after cleaning it of course). When no 12V power is applied, the valve should remain fully open. You can blow through a good heater valve with almost no resistance. If it is stuck closed, then it will be very difficult or impossible to blow through. In most cases, replacing the heater valve with a new one will solve your problem. If you need a 5-port DCCV for your 1999-(early 2002) S-Type, you can purchase a new one here. After you replace the heater valve, make sure to go back to Step 2 and bleed your cooling system.