So for about the past 2-3 weeks now my car will random turn on/off my heat. I first noticed this when coming back from my girlfriends house. I have my HVAC setting to off, and sometimes it blows out like I have it set on heat. I can slide it over to heat and nothing will change, it will still be blowing the same amount of air. Then if you just let it sit on off and keep driving it will randomly stop blowing a ton of air out of the heater spots and be like it normally was before in the on position.

So what I'm wondering is, is my heater core messed up or something?

 

Sounds like maybe an issue with your heater diverter valve. Either it's not working properly, or it's not getting a steady vacuum. Here's what I'm talking about:

http://www.autozone.com/autozone/par...13360_22457_0_

Might also be an issue with the door to the heater core opening/closing improperly. Remove the lower dash pad pass side, and watch the lever as you run the slider from warm to cool and see if the door is opening/closing.

 

The light bulb in the slider section went out about a month ago so tomorrow seems like a good time to fix that too. I'll be sure to go out and pull the cover off and look at it tomorrow.

I just replaced my heater core about 2 and a half months ago when I put new gaskets on the intake manifold. When I took the old one off I snapped one of the plastic tubes off, so I'm hoping I won't have to buy another one.

 

I agree with what Camaronewbie stated. Check those and see what you find.

 

So I pulled the lower dash piece off on the passenger side and I couldn't see the little pulley things because there were a bunch of wires in the way. I was kinda short on time so I just threw it back together without looking much.

I also went out and unplugged the vacuum line on the diverter and plugged it back in. Didn't seem to help since the heat turned on and off 6 times going to my friends house last night.

 

check the vacuum hoses controlling that make sure no cracks or not broken. if it isnt getting vacuum it wont change.

 

I'm a bit confused here. You have the top lever in the OFF position and suddenly the fan will start blowing air? If that is the case then it would be electrical related and not vacuum.

 

Yes the top level is in the off position. The car will randomly turn on the heat like you moved the lever over to heat. Last night I was on the freeway coming home from my girlfriends and I felt it kick on and stay on for a while (noting that I had the lever on OFF the whole time). Then after about 5 minutes it shut off for a bit. Then once I was almost off the freeway it kicked on again and never shut off until I got the car shut off.

 

Well the fan suddenly turning on is going to be electrical. Look at the fan switch as they get burned from the current.
The vacuum is going to control where the air comes out depending on where the lever is. If its in Off and coming out by your feet or face then the pin that rotates the vacuum selector as you slid the lever may be broke and its stuck in that one position. Or the dial that the pin rotates could be broke.
And there is a switch on top of the lever. It can get a buch of dirt in it.

May also want to check the wire harness. If you installed a radio you could have the wires rubbing behind it.

 

Ok by the fan I mean heat (sorry for confusion). I will be driving down the road, and down by my feet it will feel like I have the lever on heat. It will then random turn off, and no longer will I feel all that much airflow coming out from where my feet are.

If I slide the slider over to defrost while this is happening it will stop all air from hitting my feet and will direct it to the top of the dashboard. Once I move it back to off, it will switch back to blowing on my feet. So the lever is at least working that well.

There is a new radio installed that was put in before I even bought the car. The wiring job wasn't the best since there is a big wad of wires in the back of the car that connect to nothing and have electrical tape on the ends of them.

 

On a side note, it only seems to happen when your on the throttle. When your completely stopped it will never turn the heater on by itself.

 

 

So it has little or nothing to do with heat or the amount of air but it has to do with where the air comes out?

If this is the case, and it seems to be the case a lot in the past couple days, you are having a vacuum issue.
Vacuum controls the blend doors that direct where the air comes out.

Do you have A/C and if not did the car ever have A/C?
And if this is the case of the air comiing out the wrong vents at the wrong lever position then you need to start at your vacuum source at the manifold and follow the line checking it and what it is connected to.

 

Yeah the car has A/C. It must be the flaps because like I said every other setting works correctly except off. When it is on off its like it flips between off and heat without me doing anything. Once the wind dies down I'll get to looking at the lines.

 

Thats odd because in off the only door that should do anything is the one for the outside air. It stays open just a little to allow fresh air in. Ya know, in case ya fart.

You may need to look at the back of the switches. Circled in the pic is the valve for the vacuum that directs the vacuum to the proper blend door motors. (vaccum motors)
The funky red arrow points to a pin that is on the lever. The pin is in a slot that opperates the rotary on the valve or "switch".
Maybe you have an issue somehow with this.

 

Not that I have noticed.

 

 

So this weekend I'm going to get to the bottom of this. 3 things I need to do:

1. Make the off position actually work.
2. Get rid of the burning smell that happens when I turn the heater on
3. Change the bulb behind the HVAC slider because it went out.

How do I even get to the HVAC slider though? Do I have to take the front plate off?

And all of this started to happen after I installed a resistor to bypass my VATS. Could that have messed it up?

 

 

Had it apart today, all of the wires looked fine, what now?

On a side note, the PO somehow broke off the connector for the light that illuminates the HVAC control panel and had it attached with electrical tape. About 2 months ago the light went away so I assumed that the bulb died so I when I was looking around today I went to go fix it. I taped it to the top part of the HVAC control module but now it it makes too much shadow to see the HVAC slider still. Where is the stock location for the blub? I was trying to find it on the HVAC module itself but the wires were too short so I couldn't really pull it out at all.

 

 

Instead of fiberglass, quick steel or Oatley plumbers mend stick is great for these types of repairs. It's a clay consistency epoxy. Break off a length of the stuff and knead it together until you get a solid color. 10-15 minute working time. Usable instantly.

Degrease and roughen surfaces. This stuff is great for plastic mends or rejoining vacuum nipples and such. Also, broken clips, lips, etc. Shape it just like clay. Doesn't hold screws well for repeated service, too hard, but will hold up to a few tightens-loosenings. You can fix or reinforce just about anything with it, even paint it. It's not metal. It's just epoxy.

I too have noticed I have a problem with only having heat come out of top and bottom. I wil be going through vaccum testing myself. Perhaps when my doors operate, I can get AC cold again.

One thought too. Unplug your blower motor (super easy). See if it still acts up. Sounds like a vaccum issue though.