davidnyc06

I put the information together after searching the two part numbers and reading a bunch of different posts. I went to the dealer today and got it fixed. They wrote that they found "circuit #CHC01 chaffed near bottom of BJB. repaired circuit and reassembled."

After some internet research, I've found: Part 8C419 is the Motor Electronics Cooling Pump (MECS) that runs coolant through MG1, MG2, and the voltage converter. Part 18D473 is the Auxiliary Pump. The purpose of the aux heater pump is to provide heated engine coolant to the heater core while in EV only.

Is it the same pump mentioned in the following link? http://www.fordfusionforum.com/index.php?/topic/4194-electronic-coolant-pump/

You have described exactly what is happening with my car. I knew I was likely to get an answer on this forum. I guess I'm going to have to find some time to take the car to the dealer to get it fixed.

I was reading the manual and learned that you can't engage the ICE in Neutral. I tested this and found it to be true. However, you can put the transmission in Park and hold the accelerator to make the ICE run. Unlike the heater failure thread, my HVAC does generate heat, just not consistently in EV mode. If anyone wants to test this on a cold day, just turn up your cabin temp. I can feel a clear difference in HVAC air temp between when the ICE is running and when the car is in EV mode. I've also seen no problem with the coolant level.

To clarify the situation, the thermostat was way above "C" on the gauge, near the middle. The ICE did run intermittently throughout. However, when the ICE would shut off in EV mode, the HVAC would blow cold air. The HVAC heating demand didn't cause the ICE to run, and no ICE meant no heat. This was a problem in my situation because the freezing rain would immediately build up on the windshield without constant heat. The interesting thing I realized this month is that when I start the car on a cold morning and the temp gauge is below "C", the EATC keeps the HVAC blower at low speed until the car warms up. So everything seems to be working correctly; ICE runs when the thermostat is below "C" and the EATC has generally kept the car at the cabin temp I want. It's just that cabin heat demand doesn't cause the ICE to run.

I experienced this problem a few days ago and wonder if anyone has had a similar experience. This occurred while I was driving through freezing rain, which was freezing on my windshield. When I started the car the ICE was running and heated the cabin and windshield so nothing froze on the windshield. However, after the engine was warm, the car would run in EV mode while I drove through some downhill stretches at about 30mph. During that time the HVAC just blew cold air while in EV mode, so the rain started freezing on my windshield. The ICE wasn't kicking in because the thermostat showed the engine as being warm and I wasn't drawing much battery power. I had to slow down and tap the accelerator every so often to get the ICE running and some heat. I'm sure the driver behind me was wondering what I was doing. I had the cabin temp set to 75 and tried it in both EATC and front window defrost. I tried upping it to 85 and got only cold air in EV mode. This worries me because I was thinking if I or someone else was stuck in snow overnight, the car wouldn't be able to generate consistent heat. The ICE wouldn't turn on unless the engine temp falls or battery power is drained so the car would have to get somewhat cold before the ICE would run and the HVAC could generate heat. Has anyone else experiences this problem or is there a defect with my vehicle? Since there is no way to manually keep the car in ICE mode, I assume there is no way to ensure consistent HVAC cabin heat?