Discuss NO HEAT Troubleshooting Guide

FireRanger · #1 09-23-2011, 07:10 PM

*** 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.

tmoore78 · #2 10-01-2011, 08:53 AM

excellent work!
Sticky it!

SalRanger2 · #3 10-01-2011, 02:14 PM

Quote:

Originally Posted by tmoore78

excellent work!
Sticky it!

x2!

richarddhoward · #4 10-02-2011, 10:17 PM

Nice write up bro!

STL · #5 10-13-2011, 01:33 PM

What if you have cold air blowing out and the ac/heat is in the off position?

HazardousRanger · #6 10-13-2011, 01:36 PM

the chart is too small words are blurred...

STL · #7 10-13-2011, 01:41 PM

Quote:

Originally Posted by HazardousRanger

the chart is too small words are blurred...

Quote:

This image has been resized. Click this bar to view the full image. The original image is sized 1152x689.

Click the top of the image it enlarges.

HazardousRanger · #8 10-13-2011, 01:50 PM

errr...duhh!

thanks haha

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wow man...this is great work lol.

FireRanger · #9 10-13-2011, 02:36 PM

Quote:

Originally Posted by STL

What if you have cold air blowing out and the ac/heat is in the off position?

Vacuum line to the air damper behind the glove box is disconnected. The door has a vacuum actuator. With no vacuum, it is closed, which is the outside air position. With vacuum applied, it will open to the inside and close off the outside. This is what it does in off and also in max ac for recirc.

STL · #10 10-13-2011, 02:48 PM

Quote:

Originally Posted by FireRanger

Vacuum line to the air damper behind the glove box is disconnected. The door has a vacuum actuator. With no vacuum, it is closed, which is the outside air position. With vacuum applied, it will open to the inside and close off the outside. This is what it does in off and also in max ac for recirc.

So that would be that loud thump you hear every now and then.

Cool I will let my friend now what to check for.

FireRanger · #11 10-13-2011, 02:59 PM

Yep! When you put it to off or max, you'll here a little thump of the door shutting. The same vacuum line that does that also goes to the hot water valve to shut that in off and max ac.

hitmanbeman · #12 10-20-2011, 07:03 PM

just want to say thanks for this info freaking life saver

victoria · #13 10-26-2011, 05:04 PM

fire ranger,
I found your diagram to be informative and I hope that it works. Being a person with a sense of humor you will love the picture I paint. Imagine me, a short haired firey red head, in the back yard with tools in their neat piles. My two children (4 & 6) sitting in the grass wide eyed with glee playing with a lid from a jar. When I asked what they were doing my son replied I'm working on my new bike. Not quit understanding the comment and being preoccupied I return to the truck and its lack of heat. Long story short, 2 hours later with the truck still not fixed and tools in all four corners of the yard, I relented and ask the children what they would like to do today? They hold up the jar, now full of money, and reply Go buy our new bikes!
At this point the truck still has no heat and most of all no defrost. I have replaced the tstat, flushed the cooling system, and replaced the heat/cool control knob. I pulled the glove box and the radio and verified that the actuator doors(the 2 I can see) are intact and operate when the mode is changed on the console. The line to and from the heater core ARE HOT. But it still only blows cold air. The water pump is intact and in good condition. I have had problems with the forum because for some odd reason(story of my life) it doesn't load correctly on my laptop. Any suggestions you can make would be much appreciated (much to my children's dismay-think they are working towards a Wii now) FYI my truck is a 1995 2.3 4cyc 2 wheel drive
thank you very much, victoria

FireRanger · #14 10-26-2011, 05:42 PM

If both the hoses going into the firewall are hot, then there is hot water and it is reaching the heater core. It's got to be the blend door stuck in cold. Was your temp knob the electric or cable driven one?

jesscott98 · #15 10-27-2011, 05:37 AM

Most Valuable Thread IMHO, THANKS