As some of you know I have had several issues to deal with sense I got my 89 coupe. The car is out of winter storage and I'm back to work on it.
Over the winter I purchased a used electronic control head for the heater/ac as you could not push the cool button in (it was frozen in place) on the original head.
The blower motor appears to be operating on all speeds but the air flow will not change to the floor or defrost it stays in the vent position.
I am also not getting any heat just cold air. Both hoses to the heater core are hot when the engine is up to temp.
I’m hoping for an easy fix but I don’t think I’m going to be that lucky. Anyone have any ideas what would cause these issues?
Note that the same issues existed with the original control head too

 

First place to look is for a vac. leak. After that it might be the A/C heater programmer.

 

I'm in the same boat with my 86. Exact same symptoms

 

same thing with my 95 just no good heat luke warm

 

There is a blend door that some have reported stuck that can cause some problems

 

First start with the easy and cheap....change the vacuum check valve.
Its located under the right fuel injector cover and looks like this:

 

Anytime you disconnect the Controls, make sure memory is removed from everything - disconnect and reconnect the battery. When you fire it back up, the motor that moves the temp door, should move from fully open to fully closed and nothing will work for a couple of minutes. This is how the system learns the position of the door. If that doesn't get it working, the temp door sits between the Evaporator and Heater Core and the motor that moves it is connected to it's linkage with a plastic clip. Remove the Blower Module from the left side of the Evaporator Case and look inside to see the door. Have someone operate the Controls between 60 and 90 and the door should move. If it doesn't, the plastic clip is probably broken. The motor is accessed from the passenger's side. Remove the Hush Panel and ECM.

If the door moves, the Heater Core is plugged up. Common on the '89 since it's prone to galvanic corrosion from weeping head gaskets so if it is plugged up, you'll want to look at some other things too - like cylinder #7. Anyway, a plugged core flows coolant over the top and not through it so hose temp means zilch. If the coolant wasn't flowing, there would be a hole somewhere. Remove the hoses and try flushing it with a garden hose or compressed air.

Vent position is controlled by vacuum. Check the part - a check valve - pictured. Source is from the right side of the Plenum next to the Fuel Pressure Regulator fitting, to the Check Valve, and then back through the Firewall with the ECM harness (behind the right head) to the Programmer. That's a postcard sized device above and to the right of the Accelerator. Most vacuum problems are in the engine compartment where time and (sometimes) clumsiness breaks/wears things out.

 

ever had mice in the car. They like to eat vacuum lines in back and under the radio

 

Thanks SunCr, I guess I should disconnect the battery first and reconnect after a few minutes to see if everything resets. I did not disconnect it when I replaced the control head. As for the rest I’ll have to check out as well. Rain coming tomorrow so I won’t get back to it until Sunday (working on it outside no garage). Thanks for your help!

 

Would this be the percedure for a 95 ? Thanks

 

And a/c lines! Did a friend's van recently which was out of gas. Amazingly, negative pressure - pulling a vacuum - actually sucked in the hose and sealed it up. Didn't find the leak until I started putting some gas in it. My buddy had pointed out a couple of other things that look gnawed on before I started, but I didn't think too much of it. It was a $600 line too, but insurance covers this stuff (assuming you have Comp Coverage).

 

I have a 95 also and was have the same issue. Air would blow just never seemed to get hot. Started reading other post that led me to disconnect the hoses going into the heater core and with a water hose flush the heater core in both direction. Did not think this could do it but was a cheap place to start. Well to get to the point I did it and now the air blows very hot.

 

water valve was rusted on my 84. I bought valve for some Dodge from Advance auto. Paid $13. Also vacuum hose was rotted in right rear corner of engine compartment.

 

Different years have different designs, so it's best to stick with a single Year, but on all Electronic Units, removing power - disconnecting and reconnecting the Battery or pulling the Fuse that provides Memory Power - is like rebooting your Computer. There will be a brief delay while the Temp Door is cycled opened and closed and nothing is going to work - Blower or Compressor or even the Controls - until that chore is over. Up to 3 minutes for some. After that, it should work, but if it doesn't, post the symptoms and your Year.

 

As I said it is an 89 coupe, I disconnected the battery for about 15minutes and the unit did reset and nothing worked for a couple minutes but still not changing from vent to heat/defrost.

 

I know you posted that it was an '89, but then someone got a water valve thingy mentioned (long gone by your Year) and there was a question about the '95 which uses a different Processor/Programmer. Anyway, you will want to verify the Vacuum supply and I'd start at the source and at least follow it to the Check Valve; then remove the Driver's hush panel to access the Programmer which is above and to the right of the Accelerator. Carefully pry off the vacuum harness and there should be vacuum on the Black or source line. If there is, and with a new Control Panel, the only thing left would be the Programmer itself.

 

I hate to change the subject but I just took off the driver side hush panel to look at the vacuum to the heater and found a 2 wire harness (brown and Yellow wires) hooked up to another harness with I think it was two smaller white wires about 6 or 8 inches long that had a clamp taped to the end of the smaller wires. Anyone know what they would be?

 

don't forget that the harness is held on by a push clip and is tricky to get off. I used a small flat blade screwdriver. At least is was on my 90

 

Just looked at what I believe is the vacuum connector and it appears to have a spot for 7 vacuum lines? Sound correct? One of the spots have nothing on it the other six has a red, blue, orange, pink, black, and brown line on them. Am I looking at the right part? And should there be 7 lines on it?
L started the car and put my finger on the open spot but did not feel any vacuum.

 

There are 6 lines. It's been a long time since I poked around the Programmer so I can't remember if there is an open port, but it wouldn't surprise me if there was a vent to maintain a constant value at the Solenoids - source will rise and fall with throttle position and also relies on the Tank (left headlight well). Lines are: Black which is the Source; Red and Tan Defrost with Red always sucking it closed until the Tan Line sucks it open; Blue a/c; Pink heat and then Orange is outside air. You should feel vacuum on the Black line with the harness off the Programmer. If you don't, something between the source and the Programmer is broken.

I don't know what the electrical harness is that you found.