Heating my heater is not heating. We had this same problem last year and we were advised to replace our thermostat. We did and it worked for awhile. then we had someone come out to look at it. We were told we mixed up the wires when replacing the thermerostat. Any suggestions?

Won't work till the engine heats up, make sure you have the right fan and thermostat fitted.

You may need to replace the blower motor.Even a new one can go bad. I would try that first unless you get a professional with testers.

you may have a fail safe thermostat that is stuck open I would check that its cheaper and easier than the heater core

Did you clean sediment out of tank when replacing elements?
Did you replace thermostats? Thermostats go bad, or get out of calibration.
Copy following link for tank-type electric water heater troubleshoot:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

Test elements.
Sounds like lower element is burned out.
Clean sediment out of tank. Check for water leak running hot water out of tank by putting ear against pipe.
Replace both thermostats.

Electric water heater will last 20+ years, IF ...
Electric water heater is totally unique because it can last forever with part replacement using parts from hardware store, as long as tank does not rust because of depleted anode rod, and pressure is kept below 80psi.
http://waterheatertimer.org/How-to-maintain-water-heater.html
Annual water heater maintenance will pay you $10 a month, tax free money in pocket, by avoiding tank replacement.

R represents power supply for the heat system.
RC represents power supply for cooling system.
G represents fan (neutral).
W represents heat system.
Y represents cooling system.
Y2 represents 2nd stage cooling.
W2 represents 2nd stage heating.
AUX represents heat pump.
Try calling 1-800-468-1502.
Their english is "REALLY BAD"!!!

curcuit board issues.

by pass the thermostat

this definatly sounds like the thermostat is not opening causing presure buildup in the hoses...change out the thermostat..advised...hope that helps

Does it have batteries that need replacig. I think so. good luck.

the age of the vehicle does suggest the heater core could be plugged, when the motor has been run awhile where is the temperature gauge (if it has one). ?
If i remember right it's not that bad a job to replace the heater core in those trucks... but it's been awhile for me. I would suggest some cardboard or something in front of the rad to see if it warms up at all. if so it is likely a thermostat that needs to be replaced.

Robert