AC blows hot in front seat; cold in back seat

'99 Ford Expedition: After a long winter using only the heater, the front panels (driver/passenger) now only blow hot air (regardless of temp setting or if AC is on). The rear panels (back seats), with their separate temp controls, provide the correct temps (AC blows cold; ‘cold’ blows ambient temp; ‘hot’ blows hot).

Any ideas on how to troubleshoot this without going to the shop?


Like other Fords, that is all controlled by vacuum, so you might have a leak in the cabin behind the console.

The first thing I would do is to check the pressure in the air conditioning system. I had the same problem with a 1990 Ford Aerostar minivan. I had a leak in the line that went to the rear evaporator. Apparently, this allowed more refrigerant to flow to the rear evaporator than to the front evaporator. If this is the case, you will ultimately lose all the refrigerant. I had the system refilled which lasted for a while, but ultimately, an independent shop traced down the leak and replaced the line. It could also be that for some reason that I can’t explain, the rear evaporator seems to keep cooling on low refrigerant than the front evaporator.

If the pressures are o.k. then look for a sticking blend door.

Thanks. So, you’re thinking is that one set of vacuum lines are OK (back panels) and another set (front) may have a crack? That sounds plausible. By ‘console’ do you mean the dashboard? Taking the dash apart is over my head–I may need to take it to the shop. Any way to learn the answer (like tracing vacuum lines) on the engine side of the firewall?

Thanks. You may be onto something with the sticking blend door. Even wth no AC, I don’t get ambient air in the front panels with setting on cold (hot all the time)–so this may rule out an AC issue for now.

Is the blend door easily accessible? Or am I now into the realm of needed professional service? Is there a good repair manual (Chiltons?) you could recommend?

Thanks. I get hot all the time in front–AC or no AC–cold setting or hot setting. So maybe the blending door is the issue. Any way to view/check the blending door? Is there a repair manual you recommend?

Triedag is right about the pressures and the blend, which is the next thing I should have mentioned. It could be the actuator to the blend door that has failed or simply got stuck. I don’t know about the
Expedition, but on most vehicles it may be necessary to remove the dash in order to get to it.

As mentioned, It’s probably a problem with the blend door.

Lots of Ford owners have had a problem with the infamous broken blend door actuator.

Read the procedure for fixing it at this link:

If you are somewhat handy, you can fix it yourself for the cost of a finishing nail.