Rear heat in a 1997 Aerostar.

[Ski-Patroller]

Is the fluid flow to the heater cores controlled by a Vacuum operated valve?

Is there a separate valve for the rear heater core in a van that has the rear AC/Heater. If so where is it located?

 

[BrooklynBay]

These are the only two diagrams that I found in my Ford software:

 

[Ski-Patroller]

The 4.0L sketch only scratches the surface. My Haynes/Chilton books don't help either.

I think I have an AeroStar manual on CD somewhere. Probably the same one you have, but I'll go look for it.

Thanks

 

[BrooklynBay]

It only shows a heater control valve on the 3.0L engine but not on the 4.0L engine. Which engine do you have? If you have a 4.0L, could you take a look to confirm that there's no valve?

 

[Jose A.]

there is a second Heater Valve located on the Driver's Side, and below the rear air system, you need to look under the van, it's located to the rear of the front door.

if it's a 4.0 engine, the rear valve will be different than the valve at the front. In the 3.0 engine both Heater valves are the same. You can get replacements for those at Car Quest or Auto Zone.

 

[Ski-Patroller]

there is a second Heater Valve located on the Driver's Side, and below the rear air system, you need to look under the van, it's located to the rear of the front door.

if it's a 4.0 engine, the rear valve will be different than the valve at the front. In the 3.0 engine both Heater valves are the same. You can get replacements for those at Car Quest or Auto Zone.

Thanks

Mine is 4.0 AWD XLT

I saw somewhere that there was a second valve, but I thought it was behind the grill behind the driver seat. I didn't think to look under the van.

 

[Jose A.]

Thanks Mine is 4.0 AWD XLT I saw somewhere that there was a second valve, but I thought it was behind the grill behind the driver seat. I didn't think to look under the van.

you welcome! did you find it? driver's side, behind rocker panel, connected to coolant hose that feeds the rear air system.

 

[Jose A.]

 

[Ski-Patroller]

It only shows a heater control valve on the 3.0L engine but not on the 4.0L engine. Which engine do you have? If you have a 4.0L, could you take a look to confirm that there's no valve?

I have the 4.0L. I just looked at the heater valve and it looks the same as the 3.0 L. It looks like a proportional valve but I will need to do some testing to see if it really is. I don't know if the 3rd hose is a Bypass around the heater, or goes to the rear heater core.

I did locate the rear heater control valve behind the drivers seat, under the floor. It is a 2 port inline valve. I don't know if it supposed to be proportional, or just on/off.

Does anyone know if you can just pull the vacuum hose off the valve. It looks like they have a rubber boot, that would just pull off, but I don't want to break it. I want to measure the vacuum there and see what is going on with the rear heat.

 

[Jose A.]

the REAR Heater valve looks like the one in the picture below. I've owned 3 Aerostar, 2 with rear air system, and both valves have been the same. I believe they are Normally Open / Closes with Vacuum. (Not sure 100% on that). Otherwise they are Normally Closed / Opens with vacuum. Can't be anything else. I don't know what you mean by
"proportional".

as to the vacuum line to the valve, just pull it, (if you mean the piece of rubber at the vacuum line and valve connection, it's just a piece of hard rubber "boot" to prevent the line from getting kinked or bent.

​

 

[Ski-Patroller]

That sounds right. I think the valve in the front is proportional, ie. it opens more as you turn the heat control up.

Most car now regulate the heat with the air dampers and leave the heater core hot all the time. It's a lot easier to regulate the hot air than the coolant.

 

[BrooklynBay]

The valve is not variable. It's either open or closed.

 

[Ski-Patroller]

Does anyone know how the heat control valve under the hood is piped? Is one line a bypass, or does it go to the rear heater core?

 

[BrooklynBay]

The valve is an open/close design. No coolant flows when it's closed.

 

[Jose A.]

if you look on the passenger side of the engine, there are a number of bypass hoses connected to "T" fittings.

 

[Ski-Patroller]

The valve is an open/close design. No coolant flows when it's closed.

I just confirmed that. It closes when the Heat Control is off and Open for Vent, Floor, Mix and Defrost. I didn't check the AC, but I'm guessing the valve is closed with the AC on.

Do you know if it bypasses back when it is in the off position. There is no coolant system diagram anywhere that I have access to.

I presume the rear valve is supposed to open when the Front heater is on. Mine apparently does not open, but I'm going to have to do more trouble shooting on that. The only controls for the rear heater are the fan controls, so the AC and Heat must be set from the Front control. As far as I can tell there is no temp control for the rear heat/cooling, just the fan speed.