Write ups and tutorials for maintenance and modifications.
Sat Nov 28, 2009 3:22 am
Rick89GTS wrote:AC and HEATER FIX
Except for the AC button, ST165 AC and non-AC heater control panels are the exactly the same
1986-87 pre-facelift heater panels are not interchangeable with 1988-89 ones.
My HVAC panel with AC crapped out again and nothing was available at the junkyards. I had a spare HVAC panel without AC but I got to thinking; to speed production Toyota probably made the same circuit board with just a block-out button for non-AC cars, right? So I took apart both an AC panel and a non-AC panel and guess what? The internals are both the same.
You can simply remove the block-out button and swap in your AC button and you'll be good to go. (I had disassembled everything so I swapped the circuit board into my panel with the AC button.)
So this broadens your options if you can only find the non-AC panel and your car has AC.
CAUTION: be extremely careful if you're removing the second circuit board. It is attached to the LED's with 2 delicate plastic prongs on each side of the LED's - they break easily.
Below: the non-AC heater control panel vs AC panel.
Below: comparison between the AC button (left) and block-out button (right). Those four legs prevent the block-out button from being depressed.
Below: use extreme caution if removing this circuit board from the shell casing!
Below: this is the disassembled 'non-AC' panel. Lo and behold, underneath the black block-out button, you can see it does indeed have the AC switch. Also a good view of the fragile LED prongs and internals.
Below: another view of the internals
Below: test run to see if the AC button will work....
Below: the AC works! *HEAT SLIDER BAR*
This last pic is something that's been plaguing us 4th Gen'ers for a long time. I believe I've finally identified which leads go to the heat slider bar - they are the No. 1 and No. 10 Pins. If you resolder all the red circled points, it should fix your heat. If you try it and it works for you, post feedback
Last edited by Rick89GTS
on Sun Aug 26, 2012 3:17 pm, edited 3 times in total.
Wed Dec 23, 2009 12:40 am
hey guy, my cars heater has a reastat which is a turnable switch from left to right , thats what my dad told me, to the left makes heat come out ,to the right is cold air . My deal is i was doin some D1 in a parkn lot heat stops blown cold air ????? check connection on the reastat its good , but when switchn it back and forth it would get warm but never hot like it was before the D1. i wished i got a vid sorry but more snow to come lol
Wed Dec 23, 2009 1:00 am
Mos def a good thing to know.
801Alltrac, if the heater stop blowing hot air while driving, it could also be an indication of air in your coolant system. Which could mean two thing... One being that you simply need to burp the system or check the coolant level. The other is that your headgasket is going. It pressurizes the system with exhaust gas, causing you to have lots of air bubbles, and the coolant to evacuate via the overflow. Soooo, better check that out.
Again Rick, great post! Sticky!
Wed Dec 23, 2009 8:38 pm
Sick!! thanks Shaggz
Tue Feb 02, 2010 12:13 am
Hey Rick , I just did this on the grey non a/c panel and it works too ... still need to test it electrically ... but all the stuff was there also ...
Tue Feb 02, 2010 12:35 am
Great info here! Rick is the HVAC master yet again!
Tue Feb 02, 2010 2:42 am
Shaggz00 wrote:.....Again Rick, great post! Sticky!
88gt4DE wrote:Hey Rick , I just did this on the grey non a/c panel and it works too ... still need to test it electrically ... but all the stuff was there also ...
Good to hear it worked for you. I was able to confirm this on another panel too
88st165 wrote:Great info here! Rick is the HVAC master yet again!
Thanks, it came out of necessity. I was also able to identify the AC pins, but unfortunately didn't take any pics
However, if you take apart the board, all you have to do is follow the leads back from the AC button.MORE TIPS:
- Check the the solder points where the 2 white and blue female connector plugs join the "piggyback" board. The act of removing and replacing and/or pressure on the backside of the HVAC panel can create stress cracks on the solder joints.
- If the lights flicker or don't work at all on your HVAC panel (the little men icons or slider bar), simply check the bulbs. They are bayonet bulbs that simply twist out counter-clockwise and I found mine weren't making full contact to the circuit board. Create better surface contact with some electrical tape, a tiny bit of solder or best yet, get some new bulbs.
Wed May 05, 2010 12:33 am
The non A/C panel I had was DOA ... but others i had work great so far ... brother having intermitten issues with his .. so more to come in future with this again ...
Mon Mar 19, 2012 5:35 pm
So, does this mean that most 4th gen HVAC units will work on the trac? Just making sure since I believe the one in mine is brokken since a PO added a manual cable to open the heater.
Mon Mar 19, 2012 6:16 pm
only facelift 88-89 162's will work. the prefacelift 86-87 models are different and i think they still plug in, but nothing works.
you can tell which is which,
facelift: temp slider bottom
pre: temp slider top
since your po added a cable, a few more things:
1) i would pop out the motor above the ecu that controls the flap that directs the air to heat or cool too, check that the innards gears of it are in shape, mine were grinded away.
2) that and the cable that runs through the firewall to control the water flow in the engine bay needs to be lubed up too
Mon Mar 19, 2012 6:27 pm
Thanks for the slider info. I plan on checking all of it. The PO appears to have also removed the cable that originally ran to the engine bay, so lots of little parts to sort out.
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