'99 F-150 XLT 4.6
I get about 5 sec of heat after turning selector from off to a heat setting. Turn selector to off wait for about 30-45sec another 5 sec blast of heat ( I mean good and hot). I've checked blender door, blender motor, vacuum lines on the engine everything looks good. Really need some help, all ideas appreciated. I haven't tore into the dash yet. Was thinking about putting a HeaterTreater, but now I'm not since blender door is OK. Thanks in advance.
Turtle

 

Do not tear into the dash blindly, the problem may well be on the other side of the firewall.

Your symptom is of insufficient flow through the core. You need to get under the hood and first check coolant level, then check the relative temperature of the two heater hoses, both with the HVAC in the OFF and in one of the operating mode positions.

Report results.

 

Haven't felt of the lines yet, but I have checked the coolant reservoir. It is full. Took it for a run this morning, tried different speeds and stopped no change ( had the wife with me to feel air temp). What should I do now after feeling the hoses, say they are different temps? Thanks for the reply SHO89.

 

Say we actually check the lines first...

 

Manual or automatic climate control?

 

Hang in there with me, my truck is outside (snowing) . I'm retired and my wife's truck is in the garage (she still works) don't want her getting in no cold truck (another Ford). I was just trying to get some idea of what meant what so that trip in the cold & snow would be more than finding out one thing at a time. I'll get it in the garage Thursday (she's off), I'll get back to ya then.

 

Just a little note to say I got my heat fixed. Did a back flush on the heater core, and that did the trick. And I did check the lines first before flushing thanks to SHO89 lol. Kinda forgot that part of trouble shooting from my experience as a A/C mechanic. Kinda get a little rusty when not in use.