HVAC Vacuum Line Question

Hey guys! This is my first post. I bought a 98 XJ last week for $1000 and drove her home with no major problems other than the feared P0123 code.

Buy anyways my HVAC controls are not working they are defaulted to defrost and from what I understand its caused from vacuum lines. I replaced the line that is related to the controls and still no change BUT I have a T that isn't connected to anything on the firewall and I cant find a loose hose anywhere to plug into it. Can someone post some pics for me to see where the line is I'm missing is routed it would be a major help. Here is some pictures showing what I'm talking about. The second picture is a line coming out of the harness and I just wanted to make sure its hooked into the correct line.

Thanks!

I don't have any pictures, but there is supposed to be a black vacuum line that will come through the foam seal between the heater core hoses & A/C evaporator lines. That should connect directly to the white T in your picture.

That's EXACTLY what I needed to know. There is no vacuum line that comes through that. It looks like the heater core has been replaced before so I bet somewhere in that mix the line was not put back like it was suppose to be.

You can probably find a way to do it without pulling the dash. Here's the top of the heater box. Note the black vacuum line sticking out between the heater core & evaporator lines.

Ok cool it does look like I may be able to get around it without removing everything. I sure the heck hope so. Does that black line run to the front of the box? I tried to follow it but it's pretty hard


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Yes, it goes into the bundle and there's that connector on the front of the box. From there there's another bundle that goes to your HVAC controls. It remains black the entire time. There should be a check valve at the intake manifold of the engine. Some models have a second one at the firewall after the T (my 97 does not, my 01 does). Whatever you do, connect the HVAC controls to a vacuum source that has a check valve. Otherwise your dash vents will do funny things at WOT when there's no vacuum.

md21722 said:

Yes, it goes into the bundle and there's that connector on the front of the box. From there there's another bundle that goes to your HVAC controls. It remains black the entire time. There should be a check valve at the intake manifold of the engine. Some models have a second one at the firewall after the T (my 97 does not, my 01 does). Whatever you do, connect the HVAC controls to a vacuum source that has a check valve. Otherwise your dash vents will do funny things at WOT when there's no vacuum.

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Ok awesome! When I ran the new lines I reused all the check valves. Thank you so much for your help!!

Got it done. I had to run a vacuum line across to the other side through the firewall and back to the T. But it works perfectly now.


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