The heater in my 71 is blowing lukewarm air.

Granted, last spring I put in a 170 degree thermostat, but I recall last winter she didn't blow that warm either.

I felt both the heater inlet and outlet hoses under the hood, both are hot.

My cable to the temperature control (heater valve) is broken, but I manually moved the lever on the valve to the hottest position.

Here's another weird clue:

I'm getting moderately warm (not real hot) air from the passenger side heater or defrost outlet, but COLD out of the drivers side. I cant see any tears or disconnected heater ducts, but I'm looking today. I'm also flushing the cooling system today.

Maybe the core is stuffed. It's a bit of a mission to remove it but well worth it.

Ok well I've been flushing the system today. I now think the heater is likely working OK, based on the fact the air is pretty warm coming out of the passenger side. But definitely cold on the drivers side. And again, the inlet and outlet hoses to the heater core are both hot under the hood.

Also I noticed the control cable that goes to the blower seems ok, (the corresponding control on the panel is the off-vent-heater control). But I notice I could still push the actual lever at the blower up higher than the cable would send it. It then seemed to open some sort of door, or at least the blower system seemed louder. But this had no impact on the actual heat coming out of the vents.

Take note that the "eyeball" vents and the center vent (just below the 3 gages) will NEVER blow warm air (unless it's warm outside). They're strictly for fresh air.

Heated air flows ONLY to the Defrost vents under the windshield, OR to the side door gates to either side of the heater plenum.

That you are stating you are getting warm air out of the vents implies that the valve inside the heater plenum box has possibly lost the piece of vinyl that "seals" the opening to the fresh air vents.

FWIW

E

Trying a hotter thermostat won't hurt during the cold months. I use a 3 row radiator and 180 degree T-stat in Florida year 'round with no probs. (It's somewhere around 180 IIRC)

If it's not too cold outside you could try removing both lines to the heater and flushing in both directions. (On engine side of firewall of course)

The door you mentioned on the blower box is a recirculation or fresh air option. In frigid temps you can guess which will work better.

It's also possible that some leaves etc have gone though your system and are blocking the heater core's air flow a bit. You might be able to remove the blower box/plastic connector and carefully shop vac any offending objects from the top of the core without having to remove it.

2c

Jim

Take note that the "eyeball" vents and the center vent (just below the 3 gages) will NEVER blow warm air (unless it's warm outside). They're strictly for fresh air.

Heated air flows ONLY to the Defrost vents under the windshield, OR to the side door gates to either side of the heater plenum.

That you are stating you are getting warm air out of the vents implies that the valve inside the heater plenum box has possibly lost the piece of vinyl that "seals" the opening to the fresh air vents.

FWIW

E

E,

The heat isn't coming from the vents, only to the right side of vehicle heater "gates" or right defroster .

I may switch back to a hotter Thermostat, but still wonder why only the right outputs on the heater/defrost are delivering warm air.

The internal linkage perhaps?? There is a bar inside the heater box which goes from the cable on the outside. Are both heater doors open on "heat"?

The heater box full of leaves theory is looking better all the time.

Here's some pics of sandblasted '71 240Z under dash parts. Black stuff is crusted ospho.

I have to agree with Jimmy on the leaves stuck in the heater somewhere. When these cars sit near or under a tree the will draw leaves into the heater. When I redid my ac/heater I had so much gunk in the fan, heater core and the fresh air inlet, that I filled a brown paper bag.

try this post for some detailed help.

http://www.classiczcars.com/forums/showthread.php?threadid=32630

Edited November 24, 200816 yr by 280~Master

Here's some pics of sandblasted '71 240Z under dash parts. Black stuff is crusted ospho.

Ospho?? Which is??

Hmm well both heater doors are indeed opening.

I may look into the leaves angle, although this car is only outside when driven on Saturdays, and for short periods.

Thanks for the great link on the heater info. It's not from the regular service manual?

Edited November 25, 200816 yr by deadflo

No that information is not in the regular service manual.

I've got that same thing in an 8 page pdf. Don't know where I got it from but obviously it came from the same original source. I'll try to download it into tech section.

EDIT: The tech section won't take pdf files.

Edited November 25, 200816 yr by sblake01