Its freaking cold - HVAC -

Hey guys I had a question for someone who understands the HVAC system in a '97+ xj. It has been stupid cold this year and my hearer core isn't keeping up. I have found that if I turn the HVAC dial to AC recycle I can significantly boost the heat coming out of my vents and the pressure to which the heat comes out. However, leaving it on that setting makes my feet freeze off. IS there a way to make the recycle panel close when the vent is pointed at my feet. I know that this would require some wiring and would be happy to have the recycle only work on the switch after the mod is done. Any thoughts?

I'd be more incline to fix the heat problem than to modify something else..... Look up the methods to unclog a heater core

Its not a matter of the hetter core is broken its that the outside air is so cold that it overcomes what the heater core can pump out. Its a new core as of a year and a half ago.

And the engine is coming up to temperature / 210 or so?
I ask because when I was in Utah my '98 could keep up wtih the winter cold no problem.
As for modifying the HVAC controls / box.. sorry I got nothing. Never dug that deep in a Jeep's dash. Hell, if I can help it I never touch the dash on *any* car.

Do a search on how to fix the blend door, that could very well be your problem.

Install a switch inline on the wire that energizes the compressor. This should let you use the settings you desire to control air flow but preventing the compressor from being engaged.

My heat can keep up with Texas winters, but I plan to try this in the spring so I can take advantage of the other vent settings (be-level for example w/o using A/C).

It's just a thought at this point, so let me know if works!

yossarian19 said:

And the engine is coming up to temperature / 210 or so?
I ask because when I was in Utah my '98 could keep up wtih the winter cold no problem.
As for modifying the HVAC controls / box.. sorry I got nothing. Never dug that deep in a Jeep's dash. Hell, if I can help it I never touch the dash on *any* car.

Click to expand...

Yeah its getting to operating temp no problem. its just freaking cold outside. like -10*F. Its starting to warm up now though so maybe just not worry about it.

JPs01XJ said:

Install a switch inline on the wire that energizes the compressor. This should let you use the settings you desire to control air flow but preventing the compressor from being engaged.

My heat can keep up with Texas winters, but I plan to try this in the spring so I can take advantage of the other vent settings (be-level for example w/o using A/C).

It's just a thought at this point, so let me know if works!

Click to expand...

EXACTLY! thats what i am getting at. Nothing is broken its just that Chrysler has a weak design. Most vehicles now have the ability to recycle the air in the cabin no matter the condition. That is my goal.

XJ9694 said:

EXACTLY! thats what i am getting at. Nothing is broken its just that Chrysler has a weak design. Most vehicles now have the ability to recycle the air in the cabin no matter the condition. That is my goal.

Click to expand...

Unfortunately the HVAC doors are vacuum operated, including the Recirc Air Door, but excluding your cable operated Blend-Air Door. There's no electrical mod you can do.

The closest thing to a mod would be to disconnect the Recirc Air Door actuator and wire the door lever in the recirc position. Leave the actuator connected to its vacuum source but secure it out of the way.

As far as the AC compressor kicking in when an AC selection that you want, like bi-level, is made the compressor won't engage when the outside air temp is below 30*F. However, you will be fighting AC/Heat mix when the temp gets about this level.

A temporary fix for this is to unplug the connector on the Low Pressure Cycling Switch on top of the AC accumulator and stow it away. This kills the AC system so you can get straight heat on all 'snowflake' settings. The drawback is that you won't have defog feature when defrost or mix is selected on the mode Selector and the temp is above 30*F.

The Recirc Air Door mod and this mod are easily reversed when the temps ever get high enough in Michigan to use AC.

Chances are your heater-core is plugged... I had this issue a few years ago when I first moved to WA, winters were plenty cold and heat would barely give me +20F over outside air temp... disconnect the lines to the core, and blow it out with hose water (try blowing into both sides and see how much crap comes out) then get out the wet/dry vac to suck all the rest of the goo out.

After this, my heater keeps up and actually gets too hot when driving down the highway at speed even when it's -10 outside. Btw, I was in eastern oregon a few weeks ago and it hit -15F I had to stop to see just how cold it was. Very strange temperature, it didn't feel that cold, but it did rather hurt. We tried blowing bubbles, which froze in the air and shattered when they hit the ground, was really cool.

Also, you can do some other things to better insulate the vehicle, I have reflectix panels I use to cover the windows when I'm putting the vehicle up for the night, also a few years ago when I was working on the vehicle, I stuffed reflectix into the door panels (inside the sheet metal) and then again behind the door skins (between the inside of the door, and the trim panel inside). If you ever take down the headliner, be sure to put reflectix in as a pad/insulation layer. I originally did this to keep the AC in, but it works just as well to keep the cold out.

Thanks for all the input guys! Really appreciate it. I think I need to flush my cooling system. I did it a few years ago with a prestone system. Which puts a hose T-fitting in one of your heater core lines. So i just need to find a garage and flush it. I probably shouldn't mess with a mod and instead try cleaning my system out and go from there.

Thanks a bunch guys!

Yep.
You might be shocked how much crud can come out of a cooling system, even when you've done plenty of work on it & replaced the coolant a few times.
I know I was.
Report back with results!

The Prestone flush system is ok, however depending on how long your system has gone without maintenance it might be insufficient for what you need.

I would pull the heater hoses (the 5/8" lines), as well as the metal tubes, remove the rubber hoses from the metal tubes, clean these out with a bottle brush and the hose. Then force water back and forth through the heater core and then suck all the water out with compressed air/vacuum. Also there is a vacuum valve on the heater hose that decides whether the water goes through the fill bottle or through the heater core, this is open by default, but it's full of small openings and tends to get plugged (directing most of your hot water back through the return loop instead of through the core).

The most important things when it comes to doing a coolant flush is first getting all the old coolant out (it becomes acidic over time) and removing all of the tap water you used to flush out the coolant (minerals are no bueno inside engines). and then refilling with good quality, new coolant.

Also, I would not recommend using one of the coolant flush solutions unless you're going to replace the water pump, as the flush solutions have a tendency to cause pump failure (mostly from all the crap it liberates).

With how cold this winter has been, you can also pull the A/C clutch relay from the PDC. This will allow you to turn the dial to max ac, shutting the recirculation door while also producing heat, after the winter just plug back in the relay. (which I believe to be a win win). just a thought....

http://s266.photobucket.com/user/AHhub/media/forum stuff/2001PDC.jpg.html