Hello. Im new to the site & I think it's great! Im in need of some help with my heating system on my 66 Thinderbird. The blower blows thru both the heat & defrost air ducts, it just doesn't get warm! The air conditioner works fine, & the Radiator has been flushed & the water control valve was replaced.
Any help would be appreciated.

Thanks,
Brian66

How's the water temp? Could be the thermostat is stuck open. My F-150 did the same thing. Changed the thermostat and problem solved.

Could be a clogged core. One way to check is a little messy and crude. Disconnect the heater hoses at the core and bungy them so the ends are higher than the block so the cooling system doesn't drain.

Connect two spare pieces of heater hose to the tubes and run a hose end into one. You need to guage how much water you are pumping in vs. whats coming out. Others might have more tricks. Good luck.

The Thermostat? I'll give it a try! Thanks for the tip & I'll let you know if that's the cure.

Thanks!

If your sending unit is working and you see the temp rise from 'C' to some mid point, your thermostat is OK. (Trying to save you some work). If the temp rises only slightly above the 'C' then your thermostat is suspect. Also, one odd thing that happened to me, if the thermostat checks out and the guage is stuck on 'C', check the coolant mixture. I once got a car with about a 75% mix of coolant, works real well at giving up heat fast. So fast the car was unbearable in January. Good luck

Having to much coolant is something to keep in mind. Does the coolant prevent water from boiling? If so, I guess having to much can prevent it from getting hot. I always keep mine mixed at 50/50. that way when ever I need to add some, it's already mixed.

Have you checked to make sure you are getting a good vacuum supply to the water valve? If not, it won't open to allow water into the heater core.

I was having the same problem, I found the problem myself, if you look under the hood where the heater hoses go into the firewall you will see a diafram attached to one of the hoses, my vaccum line was off of it, I pumped it with a vaccum pump and it opened up and heat went through. I still need to find out why none of my vaccum hoses work like the emergency brake release and the rear vent. I've been trying to trace the hoses but I need a diagram.
Ron. thunder66@comcast. net

Theres a Vacuum Diagram of that system right on this web site.