what would cause no heater operation?

Check for a clogged heater core. Try back flushing it to see if it clogged. The other thing to check would be the air mix doors. Ensure they are opening and closing correctly.

This guide should help us fix it.

https://www.2carpros.com/articles/car-heater-not-working

Please run down this guide and report back.

back flushing tomorrow, but with the blend door wouldn't both hoses be hot

Yup, you are correct about that, so flushing the heater should be the thing to do first.

he is flushing tomorrow thanks any thing else no matter how small thanks

Since both hoses are not hot, I believe the passage is clogged somewhere and as thermostat had been replaced with no overheating issues, I have nothing to add to the above.

Just ensure the coolant level is correct and there are no air trapped in system after the replacement of thermostat etc.

the mechanic hasnt had time since last weekend to work on my car 3 weeks now and all has been finished is suspension needless to say a little frustrated but took it to uncle (mechanic) and he is saving me a lot of money so i cant really look a gift horse in the butt can i. that is life i suppose. but thank you for all your support and help

DI'd the problem got fix by just flushing the heater core?
Thanks...

Hello,

This problem is with the blend door actuator gears being stripped out which will not move the temperature door. Here is a guide and some diagrams to help you get the problem fixed, you can get the part from amazon.

https://www.2carpros.com/articles/replace-blend-door-motor

Please let me know what happens so it will help others.

Best, Ken

1st I had Air & Heat. Then I had air & heat, but only really cold or really hot (no in between). Then I only had really hot, no air. Then I had no heat. Then I would get heat again, but only if I turned the air conditioning on. Then I would get heat using the air or the heater. Now I'm back to no heat. Please help.

The temperature is controlled by the use of an air mix door that is operated by an electric motor/actuator. This door can be jammed or the actuator can be inoperative or have stripped plastic gears internally.

Air Conditioning problem
1998 Lincoln Navigator V8 Four Wheel Drive Automatic

My truck blows out hot air when the A/C is on. It will blow out cold air in the back of the truck but not the front. Also in the winter it will not blow out heat, but it will blow heat in the rear.

Check and inspect the air mix/blend/mode doors to include vacuum and actuators and the HVAC control module.