Like the subject says, i have no heat and the only thing that works is my defrosters on cold....I thought it was my control unit so I bought a used one and still nothing...I can adjust he speed of the fans as well...any help would be great

 

The default mode of the heat distribution is defroster. It takes vacuum to divert the flow otherwise.

Sounds like the vacuum shut-off valve on the engine is also closed, if you aren't getting any heat out. But, that takes vacuum to close, and only in max AC mode. So, you've probably got a couple of problems.

Had you done anything to the car just before this started?

 

No i don't think so..this happened over the summer and in the summer who cares about heat. Well now I do b/c it just got real cold here.What might my problems be, where should I start b/c I have no clue and gonna work on this saturday. I know that my fan switch is broken and I have recently thrown a code 43. But the light was on for about 30 secs went off and has come back on ina week.

 

Start by making sure the vacuum line for the heater control is connected. I'm not as familiar with EFI cars as I am carb, so I'm not sure exactly what that will look like or where it connects on your car.

On mine, it's a small hard plastic line that goes through the firewall.

 

Youll have to make sure the black nylon line as well as the grey one that feeds the heater valve are both still intact. Also make sure that the one way valve is still working. The nylon lines have a tendancy to get brittle after awhile and break. The ones on the efi cars are set up pretty much the same way as far as i know. The line will have a little black canister (one way control valve) connected to it and itll be off to the left of the distributer.

 

Well just checked the value and lines there all good......any other ideas????

 

Well thats pretty much the only thing that will cause what your experiencing. Inside the hvac system are a bunch of little vacuum motors that control all of the functions. As said before the default setting is defrost. So your problem is most likely if not vacuum.

 

Maybe this will help:

 

Thanks guys.....I still have no luck yet

 

Do you have a vacuum gauge?

Is there a source of at least 14" Hg on the purple vacuum line inside the passenger compartment?

If so, when you switch to full heat, is there at least 14" Hg vacuum on the blue line?

If you do not have a vacuum gauge, you should atl least be able to test for the presence of vacuum , although you will not know if it is adequate to operate the damper motors.

If you are getting vacuum at the purple line, but not the blue line, you likely have a problem with the ported vacuum switch/valve on the controls. They frequently dry out and cannot maintain a seal after 15-20 years of use. Your replacement may be no better. It's easy to disassemble the control, clean the mating surfaces, and apply a layer of silicone grease to seal the valve. Of course, the control would need to be removed to accomplish that, and you already know what's involved with that.

 

recently my heater valve broke, so i just decided to get rid of it, i ran the heater core line right into the frame rail line, and T'd off of that and put my intake manifold hose onto that, the vacuum line that was hooked into my valve i just plugged up. i just got the car so i havent really ran the heat but it just doesnt seem to be getting hot, the engine temp is perfect, runs around 160, could that vacuum hose cause an issues, just i hook it up some where or what. need help with this days are getting colder and colder.

 

Not to highjack the thread, but this is my prob. I have 2 vacuum lines disconnected under the hood, one of them broke. Its a really skinny black nylon line, and the rubber peice that plugs onto the port broke off. How do i fix it?

If i have to replace it, where is the "other" end of the line? id replace it with a regular hose.

Thanks.