It may be best to start a new thread. Title it "heater problems in 260Z" or something. There may be some differences between my 240 and your 260.

The fact that water flows one way suggests that there is a blockage at the valve. Either there is a chunk of hose, radiator sealant or the heater valve is broken internally. Try and flush with pressure in the direction of no flow. (Not too much pressure or you may damage the heater core)

As far as airflow goes... When you condenser do you mean A/C or heater core? These images may help...

With the door closed you get no flow to the lower section of the box. (Your knees and legs are not gettting hot air)

Hope this helps. You may need to replace the valve. If it's too cold out you could temporarily bypass the valve and have water flowing throuhg the core all the time. If you are saying that it does flow but in one direction you could reverse your lines for the season. My unit allows for water flow in both direstions so something isn't right with yours. (If 240 and 260 are the same)

I wanna see you keep from getting frozen as I had to make a trip in 0 degree weather with little heat once. (Had no T' stat installed)

Jim

Whoa. How to get to the valve. Well, I mean the air is blowing all of the time across the air conditioner condenser, no matter which way I slide the lever (ac/heat/def), but the lower door opens on heat. How do I manually open the heater door...I did try reversing the hoses, but wasn't sure which was "correct", the inlet from the nib on the block, or the lower feed to the lower radiator hose. Oh well...what about tje vaccuum lines?

The vacuum lines could be important. I'm not sure if a 260Z has the vacuum operated mode door actuators that the 280Z w/factory air had. If so, they could be the source of your problem. Further research shows that it does.

Nice Stephen! Had a feeling that there were differences between the 240 and 260 "boxes". Do you have a picture of the heater valve/heater core arangement? Hopefully this is as easy as hooking up the vaccum lines or replacing a dashpot. Do you think it's odd that he has only one way flow through his core?

Sorry Rebel, There are just a few differences between my system and yours. (Quite a few) The design is the same but it just looks different. On the 240 you have simple cables which attach to the dash controls. Apparently this is not the case on the 260 as it uses a more modern method of actuation... Vacuum actuated dashpots. Looking at Sblakes picture it looks like the heater core is upstream and not in the box like it is on mine. I see there is also a relay for the heater. hmmm

A picture out of a manual will tell you a lot more than anything I've shown. I'd be looking at Blakes 1st picture part numbers 4,5&6. (Heater stuff) The one way flow through the hoses still has me stumped.

Jim

Do you have a picture of the heater valve/heater core arangement?

This is the best I could find. It's from Haynes as I don't have anFSM for a 260Z.

oh that's good..thanks, bud.

Tell me: Shouldn't the heater core at LEAST feel hot or warm if water is circulating through it? Feels cold to the touch even when engine is warm

If it feels cold when the engine is running then the water isn't getting to the heater core. Sounds like the valve is stuck closed or something is blocking the flow of water to the core. This is from my 78 280Z FSM.

Then why does the water channel out when I force water through one end? Or is it by passing the core altogether..I'm not savvy enough. Thanks for the diagrams and input. Will keep plugging away.

I mistook the intake flap for the air distribution flap. I must figure out how to close the air distribution flap so the air will stop passing over the evaporator ( I originally called the condenser...I need to stick to sinmpler terminologies like "thing-a-ma-bob" and "doo-hickey")

Then why does the water channel out when I force water through one end? Or is it by passing the core altogether..I'm not savvy enough. Thanks for the diagrams and input. Will keep plugging away.

..and why would the air constantly run out the front vents only...the trap door above the matrix is tilted upward.

If the valve is closed (or stuck closed) the coolant would bypass the core. The second issue would have to do with the vaccum operated mode doors.

That's it then. The core is clogged at the valve...or the core is clogged period. My luck, prolly the latter...no, my luck prolly BOTH. OK, no sense worrying about a vaccuum issue if the core is bad. Will turn my attention to that area. Y'all have a good nite and we'll see if we can git er done next weekend.

L8r,

Rebel-Z