General Maintenance & Repairs - Should be hot by now..

I've replace my water pump, heater core and flushed my system, however it's still just lukewarm at best. Any ideas? Someone mentioned a switch or something in the dash that changes the output from hot to cold, could this be it? Any more information on that?

There is no switch or valve that opens to let water into the heater core. It flows through all the time. Have you replaced your thermostat?

Yes, I have replaced that too. What is the chance of buying a brand new bad thermostat?

There is no switch or valve that opens to let water into the heater core. It flows through all the time. Have you replaced your thermostat?

But there is a switch that controls the temperature blend door position, you know, the one with the red and blue around it. That knob controls the position of the Blend Door inside the Heat/AC box. The Blend door diverts air through either the heater core or the A/C Evaporator depending on the position of it. This controls the temperature output into the cabin. There could be an issue with either the knob, or the actual blend door can be sticking.

How can I access the blend door? Perhaps it is sticking. How can I verify that the blend door is working?

When I turn it cold from hot it does get very cold, turning it back to hot makes it go luke warm.

Since checking the blend door really involves pulling the heater box, which means pulling the Dash, I would start by doing the following:

Find an infrared thermometer gun and point it at both of your heater hoses as close to the heater core as you can access. If one temp is drastically lower or than the other, then I would say you have a restriction in the heater core. This also applies to any other areas of your cooling system.

There's a lot of advanced testing you can do with the knob, such as finding the voltage or vacuum values (I haven't looked at the system to see how it's controlled), and testing to see if you can perform a full sweep on the blend door.