1990 HVAC DIY swap

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TurnNburn
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1990 HVAC DIY swap

Post by TurnNburn »

Have a 1990 legacy with HVAC controls that dont work? Wanna swap it for one that does. Heres how. So in my experience with these first gens is that the 90' only has a different HVAC unit then all other first gens and from my personal experience and what i have read on here over the years is that this one year only (and im assuming 89, but I have not run into one of those out in the wild to verify) is known for being junk ie... not working at all and not switching modes or what have you. i have grown tired of my rally car not having heat and the ability to defrost the windshield. I have searched around and have not seen anyone even mention doing this, but i needed to do something to fix it and this is my experience with it. Hopefully it will come in handy to someone else.

Now i have a 1990 and i can confirm that mine will turn off and on randomly and will only change modes if i turn the car off, press the button for the mode i want then turn the car back on. and then it wont switch again. super annoying. I also have a 91 that worked great and i know it doesnt have the same HVAC because i tried swapping it to diag and found the connector in the back was different and did not plug in. And after a few trips the local junkyard and ripping some out i found that the 4 1990's i tried (some worked better then others but none worked 100% all of the time) only had the yellow connector with a wierd pig tail coming off of it and everything else had a black connector with no pig tail like my 91. See pictures at the end.

I obviously wasnt getting anywhere with trying to get a good used one, and buying a new was out of the question when i knew i could do some simple wiring and do it for almost free.

Step 1. Go to junk yard and pull a ''new'' style HVAC unit. There are 2 connectors, one for the blower motor control (this is not removable from the unit and swaps over no problem) it is an opaque whitish color. The other will be black. Once it is removed grab some wire cutters and cut the 16 pin black connector harness. try and get as much of the wires as possible. I was able to get about a foot ( i have a parts car so it was free but junkyard quoted me $15).

step 2. grab the yellow connector and the harness it is apart of from the 90. Cut the yellow connector off. it will not be used again but leave enough wires showing so the colors can be identified for later. In my pictures i have alread combined the harness, sorry i dont have any before pics.

step 3. Solder time. if you have the factory service manual, alldata, mitchel or haynes/chilton, completly disregard thier information as they do not have the correct schematic for the 90, but the diagrams they do have some of the wire colors are wrong. The connectors have different wire color and different pin layouts. on the yellow, 7 on top with 9 on the bottom, the black is 8 and 8. Out of the 16 wires, 10 wires share the same color... IE pin one on black is blue with a black stripe and pin one on the yellow is also blue with a black strip. solder all wires to thier corresponding color.

The ones that dont match are pin 2- red to red with black. pin 5- green with black to brown with black. pin 13 white with yellow to white. pin 14 white with green to white with red. pin 15 green with yellow to red with green. and pin 16 red with blue to red with black.

Thats it. Wrap it up and install your "new" fully functioning HVAC into your car and enjoy the sweet sweet smell of unused vent ducts! .... maybe roll your windows down and stand outside if it was as bad as mine!


Image

The yellow connector would have been attached the the whitish colored connector at the bottom where all of the electrical tape is.
Image
1990 NA 2.2 Open Light rally car
TurnNburn
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Posts: 353
Joined: Fri Jul 09, 2010 1:41 am
Location: Bend, Oregon

Re: 1990 HVAC DIY swap

Post by TurnNburn »

added pics. Also I think this might be more suited to electrical and not body, chassis and interior? I don't know, when I started I thought this would be a good home for it, but now thinking about it, it is all electrical.
1990 NA 2.2 Open Light rally car
Legacy777
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Re: 1990 HVAC DIY swap

Post by Legacy777 »

Thanks for the write-up and pictures. I'll move your post to the electrical forum.

Based on the info I have from the parts book the 90 & some of the 91 MY's. I've included that scan below.

http://main.experiencetherave.com/subar ... low_up.jpg


Regarding your original problem, I suspect the issue is due to cracked solder joints. I had this problem in 2003; the joints can be resoldered. This thread has more info.

http://bbs.legacycentral.org/viewtopic.php?f=10&t=1142
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
TurnNburn
Second Gear
Posts: 353
Joined: Fri Jul 09, 2010 1:41 am
Location: Bend, Oregon

Re: 1990 HVAC DIY swap

Post by TurnNburn »

Thanks for moving it and thanks for that first picture, its very helpful in describing what i was talking about. i had read that article and tore mine apart hoping to find some broken solder, or broken anything really. but did not come up with anything. After doing some resistance tests while it was apart i concluded my problem was in the yellow connector itself, as i could push the connector more into the HVAC and i could gain my connection again. i tried and tried to rig something up to make it permanant but i think it was just not meant for this world. So maybe this was an isolated incident on my part. i dont know. works now. haha.
1990 NA 2.2 Open Light rally car
Legacy777
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Re: 1990 HVAC DIY swap

Post by Legacy777 »

Hmm, yeah that's interesting about the connector. But at least it's working now :)
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
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