I have a 99 blazer just replaced the fuel pump as well as the front wheel bearings now the fuel guage will not work and the heater blows hot for a second then goes cold like the blower motor is just running. Help........

 

What brand sending unit/pump did you install. I hope it was a ac delco or you'll be back in it either now or later.

Make sure the connectors seated and grounds are grounded. For the heat,are you saying you have no heat? Make sure you have the proper coolant level.

 

tell us exactly what you did replacing the FP. Did you change the connector? How did you make the connections?
Did the float arm snap in securely?

 

The heater will come on at first when the car is warm and it will blow warm for a few seconds and then it wil continue to blow but the air will go cold, I am not too worried about the fuel pump I put a delco in it everything went back together ok, I think this problem is elect maybe under dash because the fuel guage doesnt work but the overhead hud will tell me my est. fuel range. Thanks for ANY ideas guys this is my dads last vehicle before he passed away and although I know its one of the "Problem child" blazers I wanna keep her.

 

See if this thread helps you out:

98+ Fuel Gauge Diagnosis

 

did the gauge work before the swap?

 

Yes it did and the heater stayed hot too gotta be electric right?

 

Try back flushing your heater core.

As for the fuel gage, well, do what has already been suggested.