I've been trying to solve a no heat issue from the wagon. Air blows cold on vent and defrost. Anyone have any helpful info on what to check ect/ I've looked at vacum lines, flushed out heater core and still no heat. Any help/pointers are greatly appreciated,thanks

You may have a failed vacuum diaphragm at the heater. You need an observer to lay on the floor and watch the system with the engine running and cycle the heater controls through all positions. That is what a smart 10 year old can do for his dad

By vent I would assume you mean the floor vent and you are getting no heat at all. The way the question is asked it makes me wonder if you have heat in one position only, or no heat at all. Being as you said you flushed it I am leaning more towards no heat at all. If no heat at all you need to make sure the cable or vacuum line actually is opening the valve in the incoming hose. The heater air box could also be plugged with debris, also make sure the motor is actually getting as hot as it should. If you mean you have heat but can't control where it comes out, then like said check the switching system.

Sounds like a blend-air-door issue to me. Common problem on M body cars.

I meant there is air passing thru defrost vents and dash vents but when i selct the temp to hot on the auto temp its still cold air- no heat.The valve on incoming heater hose from water pump has been disconeccted and i ran a stright pipe thru it now to see if that was the problem and it didn't change anything.Still blows cold.

So the hot to cold control is no longer an issue as you used a straight pipe. You flushed the core so that is not the issue. The next thing is make sure your vents are opening. That is what I guess the first answer was about. Check the vacuum diaphragm for operation. The heater box and the vents that move the air into the cabin from the air box could still be plugged with debris.

Just sell it to me to go with the 59K original 75' I've got

Sounds like a blend air door issue, the FSM had the procedures on how to test.

Do you have the AutoTemp II or manual A/C?
Two different systems altogther.

Commando

its the Auto Temp 2

Anyone have a diagram where all the vacum doors are so i can make sure they are all working?

The very first thing to do is under the hood . check the hose going to the heater and see if its hot and then check the return , if the return is cold then there is a plugged line somewhere in the heater box . if the return line is hot then you have a blend door not working.
finding the problem shouldn't be hard , fixing it is another thing especially with AC .