Adding AC to my '99 TJ - the junkyard build!

Bammo68

Bammo68

TJ Enthusiast
Joined
Dec 27, 2021
Messages
162
Location
Western Australia
So with Summer just around the corner and 110F days here in Western Australia common I figured its time to install AC into my '99 Sport. I found a local Jeep wrecker who seems to know his stuff, I read up on the parts lists for the '99 and the Jeepair guides and went picking parts.

So what I scored off the bat is a complete dash HEVAC unit - complete with heater core, evaporator and all the wiring and actuator doors etc. So that's a huge head start on buying bits and pieces and trying to mod my original one. I don't know what year it is from but the wrecker says these are common across the years so hopefully will be a straight swap.

I've ordered a new AC control head from eBay and then with the wrecker went and found all the pipework, brackets, cable clips, used compressor and a nearly new condenser. The pipework is the killer because its very specific to a RHD Jeep and very different for a '99 compared to a later model but eventually we found a complete set. The main liquid line looks nothing like LHD jeeps! This one is about 3 times as long with twists and turns galore.

I ordered a new Accumulator and a new set of O rings and gaskets along with a new orifice tube and valve service kit set from Rock Auto so I can freshen everything up before I start.

So my questions for the brains trust are:

1) I can flush out the pipes and the evaporator with the appropriate solvent from NAPA but I don't think I can flush out the condenser and I definitely can't flush out the compressor. Is there anything specific I should look for when flushing and what should I do with any oil left in the compressor?

2) How much oil do I put into the system? All the literature seems to talk about setting the level assuming some of it is already in the system but mine will be bone dry except for (presumably) some crusty remains in the compressor itself.

3) R134a is not really an option for us so looking at using HyChill Minus 30 as that is available. Should be OK I think...? I think its compatible with most oils and seems backwards compatible with 134a.

Anyway, wish me luck! Mate has a full gauge set and a vacuum pump so going to get him to help during the gassing processing. For now, its several weekends worth of arguing with the dashboard I reckon!
 
Bammo68 said:
So with Summer just around the corner and 110F days here in Western Australia common I figured its time to install AC into my '99 Sport. I found a local Jeep wrecker who seems to know his stuff, I read up on the parts lists for the '99 and the Jeepair guides and went picking parts.

So what I scored off the bat is a complete dash HEVAC unit - complete with heater core, evaporator and all the wiring and actuator doors etc. So that's a huge head start on buying bits and pieces and trying to mod my original one. I don't know what year it is from but the wrecker says these are common across the years so hopefully will be a straight swap.

I've ordered a new AC control head from eBay and then with the wrecker went and found all the pipework, brackets, cable clips, used compressor and a nearly new condenser. The pipework is the killer because its very specific to a RHD Jeep and very different for a '99 compared to a later model but eventually we found a complete set. The main liquid line looks nothing like LHD jeeps! This one is about 3 times as long with twists and turns galore.

I ordered a new Accumulator and a new set of O rings and gaskets along with a new orifice tube and valve service kit set from Rock Auto so I can freshen everything up before I start.

So my questions for the brains trust are:

1) I can flush out the pipes and the evaporator with the appropriate solvent from NAPA but I don't think I can flush out the condenser and I definitely can't flush out the compressor. Is there anything specific I should look for when flushing and what should I do with any oil left in the compressor?

2) How much oil do I put into the system? All the literature seems to talk about setting the level assuming some of it is already in the system but mine will be bone dry except for (presumably) some crusty remains in the compressor itself.

3) R134a is not really an option for us so looking at using HyChill Minus 30 as that is available. Should be OK I think...? I think its compatible with most oils and seems backwards compatible with 134a.

Anyway, wish me luck! Mate has a full gauge set and a vacuum pump so going to get him to help during the gassing processing. For now, its several weekends worth of arguing with the dashboard I reckon!
Click to expand...

Hopefully the dash you got is not an 03 or later as I don't believe the heater box is compatible with your 99. The orifice device is internal to one of the aluminum tubes so unless your equipped to replace it you may have to replace the entire line. The condenser can be flushed no problem. Grab the shop manual for your 99 in the resource section and it ill give you the oil info.
 
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You need to gas flush it with nitrogen and then evac it to see if it has integrity. There should be a label with the amount of 134 you need and the compressor should have a label for oil content. You can wing and fill until it gets cold then stop. Best way though, is with a good set of gauges the pressures and temps are available as a spec. I believe there's a few good R134 loading vids on YouTube. A good set off gauges will set you back over $100, there are cheaper ones if you not going to use them all the time. For a one time use or check you don't need premium Yellow Jacket Gauges.
 
Hey TJ4JIM - could you elaborate on what you reckon the difference would be? To clarify, I now have two complete HEVAC modules including everything shown in the diagrams below - the '99 is still in the Jeep and the new one is waiting to be swapped in. I am waiting on confirmation from the seller on what model year it is but in the meantime I extracted the parts list for the '99 and the 2004 to see if I could see where the differences lie. Its always a bit hard to know given these are RHD export Jeeps and the way they present the information seems to change from year to year but I don't think there is any dramatic differences? <edit: first two drawings are the 99, last drawing is the 04>

1999 HEVAC page 1.jpg


1999 HEVAC page 2.jpg


2004 HEVAC RHD.jpg
 
The biggest difference I can think of off the top of my head is the location of the blower motor. The early ones stick through the firewall, and the later ones are inside under the dash.

But I know nothing about the RHD models.
 
So far so good - pulled the unit apart to clean out the collected leaves etc and the evaporator core and heater core both look to be in good condition and all the flaps move easily with no issues. The unit doesnt look like the ones in the images above, its a mirror version for the RHD.

The evap core had what looks like a pre-filter or cabin filter attached to one side of it via a series of plastic X shaped tabs. The material was completely rotted out and crumbled to dust upon touching it - it looked a bit like a black scotchbrite pad maybe 1/4" thick. There is no trace of of left so I could photograph it. Can anyone confirm if this was indeed just a pre filter and should I replace if?
 
Mall'er said:
The biggest difference I can think of off the top of my head is the location of the blower motor. The early ones stick through the firewall, and the later ones are inside under the dash.

But I know nothing about the RHD models.
Click to expand...

The blower motor is in exactly the same spot as the one in my '99 so I reckon I might have dodged a bullet there! Everything seems to line up.
 
Couple of photos of the evap core showing the mounting clips for what I presume was the filter and a close of up of a few fragments that were left.

evap Core 1.jpg


evap Core 2.jpg
 
Installation continues apace. Still unsure how much PAG oil to add to the compressor though - there is nothing written on it and its an OE part.
 
Bammo68 said:
Installation continues apace. Still unsure how much PAG oil to add to the compressor though - there is nothing written on it and its an OE part.
Click to expand...

Total capacity is about 8.1oz of oil with 4 oz in the accumulator, 2 oz in the evap, 1 oz in the condenser and the remaining 1+ oz's in the compressor.
 
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