First one: My van isn't putting out a whole lot of heat here recently. What's worse is that it's sporadic. Most of the time, the heat is mediocre (even set to mega-blast furnace) to cool, but still warmer than the ambient air. Every now and then, however, it will blow out hot just like it used to. Is there some sort of valve that controls the coolant flow through the heater core that goes bad in our vans (3.0L, 1993 RWD)?

2nd, where do you find the odd battery terminal clamps that go on the end of our wires? The parts (Advance Auto) store didn't seem to have much that was similar.

 

Several things can elicit the cool/warm/hot scenario you describe. A failing fan motor could cause this, check for adequate airflow at all speeds. A loose connection between the temperature control cable and the air diversion door inside the heater box could be allowing the door to "flop" around, sometimes open for heat other times closed off. Excessive use of cooling system leak stop can also cause partial to full plugging of the heater core, something to consider if any has been added recently.

Later models were equipped with a heater diversion valve that would shunt hot water away from the heater core when the MAX A/C setting was used. These were vacuum controlled and the defaut setting is open - i.e. it requires active vacuum to close the valve and shunt the hot water. I suppose if your model has one it could be sticking in a partially closed position.

My '91 just uses standard terminal clamps - nothing out of the ordinary. Did the later models use a different style?

 

Thanks for the info on the heat thing. Adequate flow is not an issue, it just flows a lot of cool air . I haven't used leak stop in the coolant system, so I doubt that's a problem. Thus it's either the valve or a loose wire. How do I go about getting to my heater box to check this out?

They are an odd terminal clamp in that there are several wires coming out of the back of the positive (and possibly negative too) clamps that go different places. I'm just used to seeing a single wire from each of the battery terminals.

 

On the pre '92 models it was possible to remove the top of the dash cover and access the heater control cables. I'm not sure if this is still possible on the the later models. You might have someone run the temperature control **** back and forth while you listen to hear the diversion door moving within the box. If you hear a soft 'chunk' sound at the end of each position, the cable is likely operating properly. (Engine does NOT need to be on while performing this check.)

In the engine bay, with the engine at operating temperature, feel the heater hoses going to and from the heater core near the firewall. The top hose going into the firewall(heater core) is the supply line and the lower the return line. If the core is plugged the lower hose will be noticeably cooler than the top hose. If both hoses are hot the problem is either the fan or a mechanical problem (diversion door) within the heater case. If neither hose is hot, you can follow the heater hoses around from the core to the water control valve and do the same type of test to see if the problem lies there.

Might try another parts store as most carry replacement cables with one and two smaller pigtail leads in addition to the main terminal connection. You have to splice the existing smaller wires onto the pigtail leads.

You may want to post the 'no heat' question on the HVAC forum also and ask for Homer Winslow to address it, He is very knowlegeable on these problems. I believe he is a current Ford tech specialist in this area.

Good luck!

 

Great info, thanks! Out of curiosity, how many aerostars did you have to disassemble to get this know-how?

 

agelder,
You are welcome. What little I know comes solely from the only Aerostar I have owned, a 1991 model. I have done my own maintenance and repairs on various Fords for the last 30 years. The basic operating principles are the same, so what you learn on one model often applies to others as well. While other guys golf or fish, I enjoy working on cars as my hobby.

 

agelder,
Go to the Heating, Cooling, Ventilation and A/C forum and check out the second sticky note "Blend Door Problems" . Apparently there are problems with broken actuators on later models and the fix is rather simple.

 

Thanks for the info, Aero. I was poking around last night in the Haynes (i.e. mostly worthless) manual trying to figure out what to look for, but the how-to shown was much better. Looks like I have a project for the dremel this weekend