No Heat

mricci · Dec 15, 2007

With the snow the other day the driveway had to be plowed so i started up and moved the car for the first time in a little while. Its a 1990 lx with gt-40 intake as the only mod. The car started right up and warmed up to temp by the stock gauge. Everything was fine until i got in it to move it and the heater was still blowing ice cold. The first thought i had was a heater core. I was just wondering if it could be anything else before i go through the hassle of replacing the heater core.

jrichker · Dec 15, 2007

Probably a vacuum leak that disables the heater controls.

Diagram courtesy of Tmoss & Stang&2birds

mricci · Dec 15, 2007

is there a way to test if you have a vacuum leak? or just try and follow the lines and check them?

jrichker · Dec 15, 2007

Follow the lines and look for cracks, and loose fitting connections.

BlownFiveLiter · Dec 16, 2007

Jrichker, isn't the blend door cable operated? It looks like the OP has a 95 GT, in which case, it is.

Check the operation of your blend door, to see if it's in fact opening and closing. Also check the coolant level, to ensure that you don't have a heater core full of air, and that you're getting proper circulation.

mricci · Dec 16, 2007

The car is a 1990lx. I got rid of the 95 and just haven't changed the avatar yet.

BlownFiveLiter · Dec 16, 2007

Ah. Should still be a cable operated blend door, IIRC. Haven't had a Fox in 8 years, but the two are still similar in that respect.

corvetteguy · Dec 16, 2007

How long are you waiting for heat?

On warm up the gauge will go up over
normal then come back to normal. You
still will not have heat for at least 5 minutes more as
the water circulates.

Black1987Stang · Dec 16, 2007

I vote for blender door, try this.......

Warm car up good and touch both heater core hoses going into the firewall....if only the one is hot it's prob clogged or whatnot, if both are Hot, then it's most likely your blender.

Mustang5L5 · Dec 16, 2007

Blend door is mechanical. Even with a vacuum failure it should still default to blowing warm air out of defrost.

Check your coolant level. Make sure the rad is full.

Then check if both heater hoses at the firewall are about the same temp

Killer50stang · Dec 17, 2007

Mustang5L5 said:
Blend door is mechanical. Even with a vacuum failure it should still default to blowing warm air out of defrost.

Check your coolant level. Make sure the rad is full.

Then check if both heater hoses at the firewall are about the same temp

Only one that thought this? Most of the time, it's due to low coolant. Even a little bit will cause this problem. Since the air is blowing, heater blower is working. Check this first, very easy fix.

86bluecobra · Dec 22, 2007

If your rad is low on coolant you won't get heat as well. The heater core is higher then the rad so you need a full rad for it to function and circulate through it properly. I'm sure you have checked that already.

SuperStang83 · Dec 22, 2007

Make sure your coolant is full and that there are no air pockets, if there are then it will blow cold. If it is leaking from the weep hole that is when you know it is the heater core.

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