Help--Heating issue

I had heat, and now I don’t.
Here is what I have done:
New 195 deg. stat. (spring side toward motor)
Removed hoses to and from heater core, blew out with air.
Flushed heater core with water hose both directions until clear running water
The heater valve is practically brand new
New antifreeze.

I checked the vacuum at the heater switch, and there is none. This line comes from the heater core area. Where did the vacuum go?
I zip tied the heater switch with the arm all of the way in (completely open?), to hopefully bypass it and feed water to the heater core all the time, and still have no heat.

Could it be something on the heater control unit in the dash?

Just a note: the temp runs around the 1/4 mark, occasionally goes to 1/2 and the electric fan kicks on and back down to 1/4 mark

Man it is cold in Pa. right now!

I'd untie the zip tie first, that doesn't seem to be the problem (or it could be if you had it tied closed!)

No heat at all before all the work, right?

Has the Jeep always run so cool? Every one I've had runs about 1/2 on the temp gauge. That could be the reason, if you're running 100* rather than 240* it would make a big difference.

Lastly, there may be an air bubble in the system. Set the Jeep on an upslope, with the front wheels 6" to a foot higher than the rear. Start with everything cool, open the radiator cap and start it up. Let it run for at least 1/2 hour to 45 minutes, several cycles of the thermostat at least. Keep an eye on the radiator and keep it filled; you'll probably see the level drop a couple times when the thermostat cycles.

You said you failed to detect vacuum at the heater switch. In some cars, the heater valve is vacuum operated. The vacuum is modulated either by a wire or electrically. Since you have no heat whatsoever, it has to be a total stoppage in the vacuum hoses, either the hose itself ot the valve that controls water flow to the core. A minor restriction will still give you some heat.

By the way quit complaining about being cold, it was 60F this morning in San Diego and I saw a cloud out there.

I'd untie the zip tie first, that doesn't seem to be the problem (or it could be if you had it tied closed!)

No heat at all before all the work, right?

Has the Jeep always run so cool? Every one I've had runs about 1/2 on the temp gauge. That could be the reason, if you're running 100* rather than 240* it would make a big difference.

Lastly, there may be an air bubble in the system. Set the Jeep on an upslope, with the front wheels 6" to a foot higher than the rear. Start with everything cool, open the radiator cap and start it up. Let it run for at least 1/2 hour to 45 minutes, several cycles of the thermostat at least. Keep an eye on the radiator and keep it filled; you'll probably see the level drop a couple times when the thermostat cycles.

The heater switch typically has the arm out, then when the vacuum comes on it is pulled in, this opens the waterway, correct? By zip tying it open I thought the water would flow freely to the heater core???

I did have heat before the work.

Yes the jeep has run that cool since I bought it (3 weeks ago). When I bought it the elec. fan was unplugged. I assumed that the stat may be bad so I replaced it, and plugged the fan back in. The hoses get hot enough that you cant hold on to them.

If there was air in the system wouldn’t it overheat? When you say radiator cap to you mean the overflow bottle cap (closed system)?

I appreciate your quick reply.

You said you failed to detect vacuum at the heater switch. In some cars, the heater valve is vacuum operated. The vacuum is modulated either by a wire or electrically. Since you have no heat whatsoever, it has to be a total stoppage in the vacuum hoses, either the hose itself ot the valve that controls water flow to the core. A minor restriction will still give you some heat.

By the way quit complaining about being cold, it was 60F this morning in San Diego and I saw a cloud out there.

Any idea where the vacuum hose goes after going into the heater core area? I really dont want to tear the entire dash apart unless I have to.

Nice dig on the heatwave....lol. It is going down to 17 tonight.

The heater switch typically has the arm out, then when the vacuum comes on it is pulled in, this opens the waterway, correct? By zip tying it open I thought the water would flow freely to the heater core???

I did have heat before the work.

Yes the jeep has run that cool since I bought it (3 weeks ago). When I bought it the elec. fan was unplugged. I assumed that the stat may be bad so I replaced it, and plugged the fan back in. The hoses get hot enough that you cant hold on to them.

If there was air in the system wouldn’t it overheat? When you say radiator cap to you mean the overflow bottle cap (closed system)?

I appreciate your quick reply.


Well, since you had heat prior to the work, then check the things that you changed - your answer will most likely lie there.

The fan was unplugged by the previous owner for a reason. You'll probably get a straight answer from them, now that you own the vehicle.

If you zip tied in the correct position, then your solution would work. If you zip tied in the closed position, then zero flow.

I'd check the vacuum, as Mr. San Diego Heatwave suggested (:D My brother lives out there, also); but if you had heat before, then changed something, it's likely that something you changed caused the loss of heat.

It might not overheat due to a bubble in the system; since you have the closed system you can't "do" the cap open thing, but you could park it on an uphill slope and let it run, keeping the bottle full. There could be an air trap in the heater core itself. Not likely, but possible.

See also this interesting thread on the radiator, when you mentioned closed system it reminded me:

http://www.automotiveforums.com/vbulletin/showthread.php?t=482046

Yea I think we finally hit winter here in PA. That 60 on tues was nice tho, as were all the others, but it just feels like this time its gonna stay cold. The other 2 times it got a lil cold it didn't really have that "bite" to it like winter does, but tonite it sure did, even during the day it did.

All the jeeps I've seen including mine always ran around 210-220 even in the dead of winter, seems odd thats running too cold, usually problems w/ the closed system cause overheating. I had a problem w/ a 91 blazer I had running at like 110 and taking forever to heat up, that was just a bad tstat though. Just for an experiment, does it run any warmer if you unplug the fan? Maybe the fan switch is bad and its running too much, hence the reason for unplugging it. I'd test it w/ it unplugged, and see if you can find out why it was unplugged in the 1st place.

Hope that helps

Yea I think we finally hit winter here in PA. That 60 on tues was nice tho, as were all the others, but it just feels like this time its gonna stay cold. The other 2 times it got a lil cold it didn't really have that "bite" to it like winter does, but tonite it sure did, even during the day it did.

All the jeeps I've seen including mine always ran around 210-220 even in the dead of winter, seems odd thats running too cold, usually problems w/ the closed system cause overheating. I had a problem w/ a 91 blazer I had running at like 110 and taking forever to heat up, that was just a bad tstat though. Just for an experiment, does it run any warmer if you unplug the fan? Maybe the fan switch is bad and its running too much, hence the reason for unplugging it. I'd test it w/ it unplugged, and see if you can find out why it was unplugged in the 1st place.

Hope that helps

Wow is it cold this morning......lol.
Last night I removed the clip that holds the arm on the heater switch and that allowed water to the heater core. I HAVE HEAT!
The gauge will get to just about 1/2 and then drop back real quickly to 1/4.
I will try the fan.
If that is it, where is the fan switch located?
I appreciate all of the help!!

Wow is it cold this morning......lol.
Last night I removed the clip that holds the arm on the heater switch and that allowed water to the heater core. I HAVE HEAT!
The gauge will get to just about 1/2 and then drop back real quickly to 1/4.
I will try the fan.
If that is it, where is the fan switch located?
I appreciate all of the help!!

Excellent!

Now the fan....is it always on when the Jeep is running? If so, bad sensor somewhere that's not turning it off.