No heat just defrost

[89jeepxjw]

Well I posted a thread earlier to see what some gadgets were on my 89. I figured I would go buy a bulb for the clock and when I went to throw on the heat I get nothing out of the front vents but my defroster blows on any position exept off?? I can have it on vent or bi level and nothing from where it should be coming just the stupid defroster! Any help would be appreciated. I just replaced the football canister and was working great until 5 min ago, my search resulted every thread about the canister.

 

[xjwisconsin]

if you are only getting defrost then there is a vac leak somewhere in the system... look very carefully the lines are tiny and any hole will cause a loss of vac

 

[89jeepxjw]

What all runs off vacum besides the heater on a renix? Anyone removed most of the lines? What line am I looking at for heater control?

 

[Wallyman]

It may very well be behind the dash. The door that routes air from either the defrost to the vents and all that. Those are all vacuum AFAIK.
It seems like that may be an issue.Especially if you pulled the dash off you might have accidentally snagged the line. I believe you might be able to see them under the dash on the passenger side also. FYI.

 

[xjwisconsin]

I have an 88 4.0 RENIX dont know if this will help but
Green- Vac Lines for Dana 30
Blue-vac line that goes to the canister
Red-heater control valve
check the vac lines that go into the fire (the black one i circled in blue and the pinkish one that connects to the control valve) these are the hoses that control your heater

 

[old_man]

The most common problem is a broken/rotted vacuum line going to the vacuum canister behind the bumper. The place that is most commonly bad is where the black hard line runs under the battery.

 

[xjpheonix]

also check the vacuum canister behind the pass side of your front bumper it routes through there
about the size of a large grapefruit

 

[streetpirate]

mine broke on the black line going to the vacuum can right where it angles down next to the battery.

 

[Darky]

I had that problem on mine. As Old Man said it was the vacuum line where it goes under the battery. I taped it with hose repair tape and that lasted for a few months and now I've spliced new hose in and it works great. Took my cruise control with it when it first went out.