heater not not working

Question

Isuzu heater is not working despite having bought thermostats at several occasions, I checked for pipe leaks, checked for blower fan , but still cannot see the cause of the problem

Answer 1

There are a few things that could cause no heat to be coming from the vents. I'm a true believer in checking the easiest options first, so I've ordered these in that order.

1. The blower isn't working
   • This will be very obvious because when you switch on the fan, no air will blow through the vents.
   • This doesn't actually mean that the heat isn't working, per se, but that you need a new blower fan (or vacuum line). If air is blowing through the vent, it's not this.
   • Also note that your A/C won't be working if this is the problem either.
   • If this is your problem, it's generally easy enough to fix. Check your fuses, but otherwise you'll have to find the blower motor for your vehicle and replace it.
2. Head gasket
   • If your head gaskets are going, the heat is often the first thing to go. This is not a simple fix though -- you'd have to take the heads off the engine (possibly requiring taking the engine out of the car), have the heads machined, valves adjusted, and then put it all back together. It's doable, but not for the faint of heart.
   • Often times your radiator coolant will overflow (more and more often as the problem gets worse). This is caused by the compression from inside the engine pushing out into the coolant, forcing the coolant out into the overflow, and eventually onto the ground. This will also cause overheating. (No coolant > overheating)
   • Alternately, your coolant could get sucked into the engine, causing the same effect, but with different symptoms: no signs of leakage, and white smoke from burning coolant coming out the tailpipe.
   • If you leave this too long, you could build up too much pressure in your coolant system, either blowing the radiator, or blowing the heater core.
   • There is a chemical test for this where you suck air from the radiator into a tube with a liquid that changes color if there's exhaust in the radiator
3. Heater Core
   • It's different on different cars, but on my Subaru, the heater core is built directly into the center of the car. I'm certain the engineers bolted the frame onto the heater core, not the other way around. Point being: your mileage may vary, but this could be a time-intensive operation as well.
   • Basically the heater core is the part that takes the hot coolant from the engine and converts it to hot air for the interior. What goes wrong is that the heater core actually busts, leaks coolant (inside the car, in my case, but not all the time), and causes a lot of the same symptoms of a head gasket failure.

Answer 2

When the head gasket blew in my car, the heat was the first thing to stop working. I would definitely check after that. The vehicle would over-heat sometimes, but not everyday. Then white smoke started coming from the tailpipe. Hopefully it's not that, but I would check before it gets worse.