I admit it, I love my Aerostar. It's been a great vehicle for me and my family.

But they're getting old, at least mine is. 13 yrs old and 138,000 miles. Still our primary vehicle and will be untill it starts needing too much work, which it does NOT yet.

But it's needing a more and more non-routine maintenance and attendance as time goes on. Which leads me to the title of my thread.

My heater is barely kicking out any heat. The blower works fine and it has plenty of coolant in the radiator, though there doesn't seem to be much in the heater core lines, and they're lukewarm to the touch, the back one cooler then the front one. The thermostat is new a few weeks ago.

Before this winter, the heater would bake you out the van, regardless of outside temp.

I'm suspecting the heater hose bypass valve on the heater. I could not get it to move using the controls. I can move it manually, but the HVAC controls do nothing.

Anyone know how to tell if it's good or bad? And where to check for a vacuum issue. I changed the alternator a few months ago and may have done something to the vacuum source for the heater bypass valve.

Thanks in advance.

P.S. Take a close look at my avatar. I can tell what kind of vehicle is behind my highboy. Can you?

 

The default setting on the heater valve is in the open position- i.e. it must have positive vacuum to operate. While its possible it could be stuck partially closed, you can easily tell by feeling the hoses on the inlet and outlet sides of the valve. If both are equally hot, the valve is open. Its more likely you are experiencing a partial plugging of the heater core(s). Often, just back flushing will clear them. Of course, it would be wise to flush the entire cooling system at the same time. There are various postings on this forum regarding flushing and heater cores.

When changing the alternator, you could have easily snagged one of the vacuum lines. Look at the off-white colored ones in particular. They become brittle with age and break easily. The good news- you can buy connectors for the tubing at most parts stores. (Look in the HELP! section or on the revolving carousels with the miscellaneous items.)

 

Are you talking about the plastic vac operated valve on the coolant intake side of the heater core? If so should get a bypass in the OFF & AC positions only, otherwise you should have flow through the heater core. Put the heater control onto OFF or AC & you should hear the valve operate (& see the actuating lever move) when you pull off the vacuum line & then replace it. If nothing..... either the valve is stuck or you have no vacuum. Test for vacuum with your finger , you should feel it suck to your pinky.

If valve operates properly yet the intake & especially outlet pipe is still cold, something is blocked. Drain down the coolant a gallon or two & backflush the heater core & also check that the bypass valve is not blocked. If coolant is not nice & green & at least 50% strength you'll need to flush & replace the whole coolant system.

ATB Aeroman.