Topic: No heat

[cletz97]

The heat in my jeep does not work. Its 38 degrees out today and i need help. Is it something i can do? or should i bring it to the shop and have them do it? and if that how much would it cost for both?

[Jeffy]

Check the vacuum lines to the dash.  There should be a green one and I think a clear one.  They end up at a manifold behind the cigarette lighter.

[MYSTANGT]

Back-flush the heater core. Very typical issue with TJs.

I had the same issue, back-flushed mine and now its smokin' HOTHOTHOTHOT   

[Sidscan]

I had a broken thermostat.  Once I replaced that I got heat again.

[MYSTANGT]

It can very well be the tstat, you are right. But a stuck closed/open tstat will give more symptoms other than just no heat.

The jeep would run too hot or too cool. But yea it is very possible. I thought that was my problem too and I replaced it with a Stant 195*

[Jeffy]

It can very well be the tstat, you are right. But a stuck closed/open tstat will give more symptoms other than just no heat.

The jeep would run too hot or too cool. But yea it is very possible. I thought that was my problem too and I replaced it with a Stant 195*

I think most will stick closes and you'll see the temps ride on the gauge then when it gets around 230* it usually has enough pressure to blow the valve open then your temps should drop significantly till the cycle starts over again.

I would try disconnecting the heater hoses from the pump and thermostat housing and run a garden hose though the lines.  Run it in both directions.

There is also a vacuum line that controls the heater as well.  The manifold is above the ash tray.  The manifold should have three ports but only two lines.  One is green and the other is clear I think.  Without moving teh middle one, you can move the outer one to the other slot and the heater core should heat up without having the heater on, IIRC.

[MYSTANGT]

I think most will stick closes and you'll see the temps ride on the gauge then when it gets around 230* it usually has enough pressure to blow the valve open then your temps should drop significantly till the cycle starts over again.

I would try disconnecting the heater hoses from the pump and thermostat housing and run a garden hose though the lines.  Run it in both directions.

There is also a vacuum line that controls the heater as well.  The manifold is above the ash tray.  The manifold should have three ports but only two lines.  One is green and the other is clear I think.  Without moving teh middle one, you can move the outer one to the other slot and the heater core should heat up without having the heater on, IIRC.

But wait, what exactly does that vacuum do? Does it engage the blower? What is its function?

And if you were to switch the hoses from one port to the other the car would constantly allow heat in without the blower being on?   

If thats the case, I am about to toy with that and move the line over for the winter time so that the Jeep always has heat working and not loose any power from using the blower motor. 
This would be awesome especially since my blower steps 1 & 2 dont work so I only have heat on 3 & 4 and its noisy and i constantly have to keep turning it on and off since it gets too hot then cools, yatta yatta yatta....

Am i thinking correctly here?   

[chardrc]

I think most will stick closes and you'll see the temps ride on the gauge then when it gets around 230* it usually has enough pressure to blow the valve open then your temps should drop significantly till the cycle starts over again.

how do you fix said problem... i replaced my t-stat and it still does that annoying cycling  ... possible that i got a defective t-stat or something? sorry for the sidetrack / thread jack.. could split off to a new thread if necessary but seems like it would be a one post answer kinda thing...

[Jeffy]

how do you fix said problem... i replaced my t-stat and it still does that annoying cycling  ... possible that i got a defective t-stat or something? sorry for the sidetrack / thread jack.. could split off to a new thread if necessary but seems like it would be a one post answer kinda thing...

Buy a quality thermostat.  I got fed up with the Stant's and went with a Robertshaw that is all brass and copper construction.  These cost a lot more $10 v. $2 but well worth it.

[Jeffy]

But wait, what exactly does that vacuum do? Does it engage the blower? What is its function?

And if you were to switch the hoses from one port to the other the car would constantly allow heat in without the blower being on?   

If thats the case, I am about to toy with that and move the line over for the winter time so that the Jeep always has heat working and not loose any power from using the blower motor. 
This would be awesome especially since my blower steps 1 & 2 dont work so I only have heat on 3 & 4 and its noisy and i constantly have to keep turning it on and off since it gets too hot then cools, yatta yatta yatta....

Am i thinking correctly here?   

The vacuum is used to control a door (Air Door) in front of the heater core.  If you leave the door open heat should migrate into the cabin.

[roksld13]

Another thing bout the thermo....  You can get a fail prof. so when it does fail it always sticks open. I always use them, there like 15 bucks but its worth it.  Is the jeep running at the right temp or lower.  If its lower then it may very well be the thermostat, if its the right temp but no heat then i would say the heater core.  there is also the temp sending unit on the thermostat housing, that thing can go bad also.