Trouble with heater

nstroud33 · 06-05-2014, 06:11 PM

I have a 1988 Supra that I just bought. I found out the heater is not working, the A/C works fine. Any suggesting where I should look first.

Busted Knuckles · 06-06-2014, 08:43 PM

There's a vacuum-actuated valve on the passenger side firewall that controls the coolant flow to the heater. The vacuum is turned on and off with a vacuum switch controlled by the climate control module. This switch goes bad after many years of service. You can see if the valve is opening by starting the car and seeing if the lever on the valve moves. If it doesn't, route the vacuum line past the small switch and straight to the vacuum port to see if the lever moves then. I needed to do this to my car 3 years ago, and I still have the switch by-passed and the heater working fine.

cre · 06-08-2014, 05:25 PM

The details about the HCV and how to bypass it are in a thread in the MKIII FAQ section.

06-05-2014, 06:11 PM	#1
nstroud33 Stock Join Date: Jun 2014 Location: san diego Posts: 2	Trouble with heater I have a 1988 Supra that I just bought. I found out the heater is not working, the A/C works fine. Any suggesting where I should look first.

06-08-2014, 05:25 PM	#3
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	The details about the HCV and how to bypass it are in a thread in the MKIII FAQ section. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

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06-06-2014, 08:43 PM	#2
Busted Knuckles 12psi boost Join Date: Dec 2007 Location: Atlanta Posts: 300	There's a vacuum-actuated valve on the passenger side firewall that controls the coolant flow to the heater. The vacuum is turned on and off with a vacuum switch controlled by the climate control module. This switch goes bad after many years of service. You can see if the valve is opening by starting the car and seeing if the lever on the valve moves. If it doesn't, route the vacuum line past the small switch and straight to the vacuum port to see if the lever moves then. I needed to do this to my car 3 years ago, and I still have the switch by-passed and the heater working fine.