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Heater Issues

16guns

16guns

NAXJA Forum User
Location
Portsmouth,R.I.
My 99 now changes the heat direction without changing the knob. It starts blowing towards me then it redirects itself towards the defroster. So is it a vaccuum line/leak or ????? I have tried looking at other threads but nothing is listed with the issues mine is having. I think it is a leak but it's just a guess from looking at other threads.
 
most likely is that the vacuum into the HVAC control unit is bad. typically this is because somebody disconnected the reservoir bottle under the bumper. there is a hard plastic tube that runs under the firewall pinch seam that serves the A/C, cruise control, and other stuff, follow it around and look for damaged or disconnected tubes
 
ehall said:
most likely is that the vacuum into the HVAC control unit is bad. typically this is because somebody disconnected the reservoir bottle under the bumper. there is a hard plastic tube that runs under the firewall pinch seam that serves the A/C, cruise control, and other stuff, follow it around and look for damaged or disconnected tubes
Click to expand...

I know the HVAC & Cruise are connected, but would a bad HVAC control panel make the cruise not work?

I've been through my 97 looking at the hard lines that go from the intake manifold to the reservoir, and can't seem to find a leak under the hood. I was starting to suspect that it was somewhere in the dash.
 
dagr8tim said:
I know the HVAC & Cruise are connected, but would a bad HVAC control panel make the cruise not work?

I've been through my 97 looking at the hard lines that go from the intake manifold to the reservoir, and can't seem to find a leak under the hood. I was starting to suspect that it was somewhere in the dash.
Click to expand...

Because the cruise control servo gets vacuum off the same line as the HVAC controls.
 
It's pretty common to find a cracked plastic hose (the vacuum line to the reservoir behind the right front bumper) right next to the battery. Seems kinda funny that they would use a plastic tube that can be eaten by battery acid doesn't it. It can appear like a discolored area which has small cracks.
 
MJR said:
Because the cruise control servo gets vacuum off the same line as the HVAC controls.
Click to expand...

I know that. I'm wondering if there is a check valve setup on the HVAC control panel. If not, installing one on the line that goes through the firewall should allow you to test if it's the HVAC setup that's leaking.

Ofcourse you could disconnect the "T" at the firewall where the small line goes through the firewall and put a vacuum cap on the nipple to the HVAC. That way you could test if it was the hard lines/ reservoir under the hood, or if it was the HVAC setup that was leaking.

While we're on the subject tho, is it possible that an old engine (260K) just isn't making enough vacuum anymore?

BTW, in my case, I'm working on a 97 XJ.
 
dagr8tim said:
I know that. I'm wondering if there is a check valve setup on the HVAC control panel. If not, installing one on the line that goes through the firewall should allow you to test if it's the HVAC setup that's leaking.
Click to expand...

The check valve should be at the intake manifold on the line. I doubt it's the dash side unless a passenger kicked/ripped off a vacuum line with thier feet.

dagr8tim said:
While we're on the subject tho, is it possible that an old engine (260K) just isn't making enough vacuum anymore?

BTW, in my case, I'm working on a 97 XJ.
Click to expand...

I don't think it would run. I have seen 4.0L's with over 325,000 on them.

dagr8tim said:
I've been through my 97 looking at the hard lines that go from the intake manifold to the reservoir, and can't seem to find a leak under the hood. I was starting to suspect that it was somewhere in the dash.
Click to expand...

It's possible your problem isn't even vacuum related. Have you noticed any problems with the vents? You might have an electrical problem. Any codes with a scan tool?
 
Last edited:
mine would do the same thing, one of the actuator arms was broken, JP has a feature on this in their tech section of their website. (97+) It's easy to repair but tough to get at. Look at the JP write up (same heater box) and pull the stereo, it's on the left side. as you look in the hole.
 
MJR said:
The check valve should be at the intake manifold on the line. I doubt it's the dash side unless a passenger kicked/ripped off a vacuum line with thier feet.



I don't think it would run. I have seen 4.0L's with over 325,000 on them.



It's possible your problem isn't even vacuum related. Have you noticed any problems with the vents? You might have an electrical problem. Any codes with a scan tool?
Click to expand...

My situation is that the cruise doesn't engage, but lights the indicator in the cluster. I always get alittle air out of the defrost, no matter where the selector is, and I think I'm hearing the blend door smack open/closed when
I start or turn off the Jeep.

I guess I wait until it warms up a bit and take another run at the vac lines.
 
dagr8tim said:
My situation is that the cruise doesn't engage, but lights the indicator in the cluster. I always get alittle air out of the defrost, no matter where the selector is, and I think I'm hearing the blend door smack open/closed when I start or turn off the Jeep.
Click to expand...

http://www.naxja.org/forum/showthread.php?t=1020640

It's possible still vacuum but you can still have a light and have an electrical problem. The other common problem is the brake light switch as it provides power to the cruise control servo. If you had a 12V speed control circuit error code I'd say it was the brake switch.
 
MJR said:
http://www.naxja.org/forum/showthread.php?t=1020640

It's possible still vacuum but you can still have a light and have an electrical problem. The other common problem is the brake light switch as it provides power to the cruise control servo. If you had a 12V speed control circuit error code I'd say it was the brake switch.
Click to expand...

Only code I get is the O2 sensor out of rage. The PO removed the cat and rear 02. I've got a replacement cat and 02 when it's warm enough to replace.
 
dagr8tim said:
Only code I get is the O2 sensor out of rage. The PO removed the cat and rear 02. I've got a replacement cat and 02 when it's warm enough to replace.
Click to expand...

With a scan tool? Factory or aftermarket? I've been able to get codes on the OE tool you might not get on a aftermarket one. Besides you can check all the inputs and even actuate the servo with the factory one which is very handy.
 
MJR said:
With a scan tool? Factory or aftermarket? I've been able to get codes on the OE tool you might not get on a aftermarket one. Besides you can check all the inputs and even actuate the servo with the factory one which is very handy.
Click to expand...

Sadly, I'm not in a hurry to pay a dealership to use their scan tool.

At this point it's just an annoyance, that's why I haven't torn it all down and fixed it.
 
I found the crack in the hard line and used electrical tape. It seems to work now.....Thanks A lot everyone!
 
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