aroulette

I have seen a few posts on how to fix this problem. I have even seen pics of burned fuses that need replaced. Where should I start?

jimswhite92

I would first check both of your heater hoses and make sure they're both hot. This insures hot water is flowing through the heater core. If one is hot and the other is not may indicate a restricted heater core.

jmrl98

Check your hvac. On my 85 the elbow piece that connects the hvac sytem from the plenum to the fire wall was cracked, creating a mean vacuum leak with the same symptoms you're having. The hvac line on our cars is from the back passenger side of the plenum to the fire wall. Good luck! :seeya :steering:

jackdaroofer

:iagree: All of the above!

Also....

The heater system involves a constant flow of coolant through the heater core even if heat is not called for. Hence the suggestion to check the heater hoses.

Recently one of our members solved this problem by "flushing the heater core"

GM installs a "door" in the heater box. the door is closed when heat is not required, thereby isolating the constantly flowing hot coolant from the interior.

If the heater door doesn't open when heat is called for then you will not get heat.

Again, there have been numerous posts on this subject

Search the archives, or if you wait a little while and keep moving this post to the top, someone will have your answer

:steering: [ I love that Lil Guy! ]

aroulette

where is the hvac?

aroulette

anyone?

jimswhite92

Have you checked the coolant flow ????

Were both hoses hot ensuring water flow through the core ???

Haven't heard of HVAC. I'm gonna search for a similar problem that located some of the components with pictures, etc.

Siveck

Do all functions except for the heat work? (defrost, front vents, lower vents)
I'm assuming that the only problem is that you don't have heat. All other operations work. Now, let's narrow the problem down. Open your hood. Go to the passenger side. Look for a big black box on the firewall. It has AC lines routed thru it. On top of this box, you will see a module with a harness attached. This is held in place by 3 7mm screws. This is a heat sink. Remove the screws and pull it out. Now, take a flashlight and look down in the hole towards the passenger side. You will see the hot/cold door. It should move when you go from hot to cold or vice versa on your climate control. If it does not move, then this is the problem. (it should only take afew minutes to do this.)
Now, if the door is not moving, then it is probably the resistors (you referred to as burnt looking fuses-they are resistors). What you need to do is pull the hush panel under the steering column under the dash. On the firewall above the gas pedal, there will be a black box. Unbolt it and drop it down. Unplug the wire harness. Now pull the circuit board out of the box. It will be attached to several vacuum lines. Make a diagram as to where these connect because not all of them are color matched. Now you have the circuit board out. You will see two big resistors on the corner. The board will be dicolored from the heat. The solder joints need to be resoldered at these two resistors. Now put it back together and your heat should work. Mine did. I hope this helps. :auto:

Steel Blue 91

HVAC refers to the Heating, Ventilating and Air Conditioning that is controled by your climate control system. Do you have the automatic climate control? If so, some of the connections on the circuit boards may be corroded. This may cause the heater door not to open. There is a tech tip on removing and cleaning the connections.

ZR_Don

I suspect a clogged heater core. This happend to me with my old 94.

At the suggestion of a forum member, I ran a garden hose through the heater hoses and flushed the core both ways. It is amazing how much gunk builds up in there. This solved my problem and it was a "free" fix.

Good Luck!

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ZR_Don

90 ZR-1 (no.2249) Red/Red,:reddevil
12.716 in the 1/4 - 337 at the wheels

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