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Old 09-23-2011, 07:10 PM
FireRanger FireRanger is offline
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Default NO HEAT Troubleshooting Guide

*** WORK IN PROGRESS ***

These two troubleshooting flow charts will guide you through figuring out why your heat isn't working. The V6 and 4cyl engines have different cooling systems so there are two different flow charts. Further below you will find photos of the various components. Thanks also go to SheltonFilms for input on the nuances of the 4cyl cooling system which varies greatly from the V6 engines.

As with any troubleshooting guide, I've tried to cover as many variables as I can within reason. This should cover 90% of the problems you could experience. But, if you are the 10% experiencing something ridiculous, there is just no way to capture that in a chart. For example, if you have a 4cyl with a simultaneous clogged heater core, stuck hot water valve, and a slightly rotted out water pump, I can't make a sidebar for that.

V6 ENGINES CHART
Chart by FireRanger



4cyl ENGINES CHART
Chart by FireRanger




New vs Rotted Water Pump
Notice on the old one, the impeller vanes are completely rotted away. This pump will move some water but not enough. A pump like this will not be able to push hot water all the way to the heater core. It will probably also cause overheating of the engine eventually.
Photo courtesy SheltonFilms.




V6 Engines Only: Hot Water Valve
This is the hot water valve that closes in OFF and MAX AC. Vacuum operated. It is located towards the lower front of the engine near the water pump on the hose supply hot water to the heater core.
Photo by FireRanger.



4cyl Engines Only: 4-Port Hot Water Valve
This is the hot water valve that bypasses the heater core in OFF and MAX AC. Vacuum operated. It is located towards the lower right front of the engine. Water either flows through the heater core or directly back to the engine block.
Image courtesy SheltonFilms / Alldata






Blend Door Actuator
This is what moves the blend door to direct air through the heater core. It can be electric or manual (push/pull cables). Which one varies by year and whether you have AC or not. If you have a bunch of wires, it is electric. If you just have two cables, it is manual. Installed photo is of the manual one in my '03. You can reach it by dropping the glove box.
Photos by FireRanger, STL, & rwenzig

Installed manual blend door actuator



Manual blend door actuator connected to the HVAC control panel by cables.



Electric blend door actuators



Electric blend door equipped HVAC controls



4.0 Thermostat
Thermostat on the 4.0L V6.
Photo by FireRanger




I have more I want to add to this but I figured I would get this up before I go away for the weekend.
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