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Greg A
Greg A, Master Troubleshooter
Category: Chevy
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Experience:  Working with Electronics & Cars for 25+ Years
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1997 4.3 astro van. I have no heat to the rear heater. Is ...

Customer Reply

Customer: replied 7 years ago.
1997 4.3 astro van. I have no heat to the rear heater. Is there a valve to control this either by vacuum or electric and where could i find it.
Expert:  Greg A replied 7 years ago.

HiCustomer Thank you for asking your question on Just Answer.

I am not quite clear on what you mean by "there was no hot line to the rear."

Are you referring to a coolant line (hose), so that there is no hot coolant going to the rear heater core?

Or are you saying that there is no POWER to the rear blower, so that NO AIR is coming out of the rear heater?

Are the coolant lines to the rear heater core (under the van) HOT to the touch?

Thanks, XXXXX

Customer: replied 7 years ago.
There is no hot coolant on the lines to the rear of the van. I started from the back and followed the lines to the passenger side under the ac condensor and there is a vacuum junction of sorts at that point where there is hot lines.The blower works good. Maybe i can hook into the line for the front heater core to get heat to the back for the rest of the winter but would like a better option if there is one.
Expert:  Greg A replied 7 years ago.

Hi again.

I have some information from the 1998 model of your van, but this should be pretty close to the same as yours.

Here is the description of the rear heater:


And here is the schematic:


Here is a diagram of the valve location I found.


You will notice the "Heater Control Valve Solenoid" in the lower left of the schematic. What could be happening is that the valve has gone bad. You COULD just bypass that valve, until you get a replacement, by putting a straight piece of pipe in there.

What I would do is check that there is power and ground at the terminals of the connector for the valve when the ignition is switched to RUN (engine off) and the blower motor for the rear heat is set to LOW, Medium, or High. Then switch the blower to OFF and see if power "goes away". You might want to ask someone to help you with this, so you can hear or feel if the valve & solenoid is clicking or moving when switched from OFF to one of the other settings.

Once you check that the voltage is switching properly, you should start the engine and allow it to warm up, then switch the blower on and see if the hoses get hot, past that valve, after a minute or two. If not, the valve will probably need to be replaced.

I also checked at, and they show that the valve should look something like this:


Please let me know what you find.

Take Care, Greg A.

P.S. I almost forgot - you might want to take the hoses loose that run to the back heater core and run water through the rear core system, in both directions, to make sure that you have good flow to the rear core.

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Greg A
Greg A
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Working with Electronics & Cars for 25+ Years