that was happening on my 99 f250sd 7.3 and it ended up being the fuel heater under the fuel filter was shorted out.
Heater hose or heater core.
the heater core could be pluged or the heater control valve is stuck closed
You may be refering to the glow plugs. They help the engine turn on.
Intake manifold gaskets are leaking, intake manifold is warped.
Check for spark at the plugs. Check for fuel to the engine.
Bad plugs, wire , or coil pack.
Yes it could also cause the A/C to stop working.
The heater core is probably to blame, it has developed a leak.
Coolant leak? Check your heater core.
There are several common heater problems for a 1997 f150. A stopped up or leaking heater core, bad thermostat or clogged up blower fan housing all can cause heat problems.
Check the distributor. That is the most likely cause, or the crankshaft sensor.
Blown fuse.