Replace Heater Core

Here's some good repair guides for your Tercel :) Look here for help first!
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Re: Replace Heater Core

Post by SynthDesign » Sun May 22, 2011 2:37 pm

takza wrote:
hberdan wrote:Great Info! I've been putting this repair off for a couple of years. Now I have no excuse!
By the time you've finished you'll wish you had found one? :roll:
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Re: Replace Heater Core

Post by hberdan » Sat Sep 24, 2011 8:04 pm

Yeehaa! I did this! The instructions are almost perfect. It is very tedious, and like sdoan, it took a full 8 hours, and maybe a couple more overall, since I spent some time washing and cleaning all the dashboard panels and trim that I removed, to get out 24 years of dust and debris. The old heater core seemed to be the original one, and the old heater hoses had to be removed by cutting with a razor knife--the hoses were virtually welded to the inlets and outlets--then replaced with new hoses and clamps. I also used various thicknesses of foam insulation tape, depending on which duct I was installing--not only the previously mentioned 1/4x3/4 tape, but 3/16x1/2 came in handy on the various r/l ducts. This old plastic ductwork seems pretty fragile (or friable), so I didn't want to force too much of a fit on some.
And thanks to Petros, (who also provided the core), I replaced the heater control panel and cables, as my old one had broken. Fwiw, it was much easier to remove and install the heater core without the control panel hanging in front--since I was going to replace the old one anyway, I just detached the cables at their far ends, the electrical connector for the fan switch, and removed the entire mess. There is a second connector in ther if you have AC. I installed the new panel after getting the heater unit in place, and then threaded all the cables and connectors, etc.
Still, very tedious work on your back, or sideways, working under that dash. My dash and interior are all black, which caused some low light problems until I got my headlamp outta my rucksack.
Be sure and pay strict attention to the routing of the cables, and take care to properly install the door lever onto the drivers back side of the main duct.
As an added bonus, while I was under the dash, I REMOVED the darn seat belt and door buzzer. Nice. It's not necessarily something to recommend if you are prone to accidentally leaving your keys in the ignition, however.
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Re: Replace Heater Core

Post by Mad_Marx » Sun Aug 11, 2013 3:45 pm

Thanks for the write up, I'm in the middle of this operation now, cleaning mouse nest and 26 years of patina out of all the air ducts. For some reason the pics for the original post don't show on my end. Is this a setting I missed somewhere?

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Re: Replace Heater Core

Post by dlb » Sun Aug 11, 2013 6:50 pm

the pics don't show up because they were hosted by an old server for the forum. once the server changed, all those photos were lost. it's a bummer.

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Re: Replace Heater Core

Post by sdoan » Tue Apr 15, 2014 10:36 pm

Managed to edit the original post to replace the photo links so that the photos are visible again. Hope you find this helpful.

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Re: Replace Heater Core

Post by Gottolovem » Tue Apr 15, 2014 11:16 pm

Thank's for taking the time to repost the photo's.
My second tercel was 400 dollars needed a tranny and the duct work including the new heater core was piled up in the back of the car. Not knowing how it came apart it took me all day to puzzle pice it back together.
I actually enjoyed the challenge but recall my gut and neck killing me the next day from sitting cockeyed all day in the car :lol:
All these photos would been very helpful
Last edited by Gottolovem on Thu Apr 17, 2014 11:24 pm, edited 1 time in total.

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Re: Replace Heater Core

Post by ARCHINSTL » Tue Apr 15, 2014 11:47 pm

PROPS, Sean - Thanks!
Tom M.
T4WD augury?
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Re: Replace Heater Core

Post by Mark » Thu Apr 17, 2014 9:05 pm

I made the horrific mistake of taking on this job. I just finished, and I'd never do it again. It was actually more frustrating than removing/rebuilding/replacing my automatic transmission. It took me about 4 days (working a few hours a day). I had to re-weld the steel heat control lever since it broke in half (one of the reasons I decided to start this job). I spent all day today trying to align all the control wires/flaps/levers/ It now sort-of works.
Never again!

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Re: Replace Heater Core

Post by NWMO » Fri Dec 16, 2016 12:22 pm

Hey all,


So, it looks like it is my turn to have fun. I was feeling pretty good about things (thanks to sdoan, wow!) AND then Mark throws cold water on me :D :D I've been trying to make time to do some frame/floor pan rust repairs as well, after viewing the pics, it seems like mission creep before I even start, needed regardless. Unfortunately we are supposed to be getting our first snow/ice combo today/tomorrow and I will probably be in my boss' 4WD work truck instead of the Rusty Frog :x. Oh well, it's early, I'm sure we'll get some more winter precip down the line.

I'm going to try and get a new heater control valve cable as well. It wouldn't be bad to have it adjustable from inside the car, though I know it isn't necessary Tom :lol:. Thanks again to sdoan for sharing and Tom for linking this. Great help.


PS - I did start in the OM, but didn't find the right section (if there is one).
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain

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Re: Replace Heater Core

Post by grouchytom » Fri Feb 03, 2017 9:47 am

Thank you for the write up. Still sucked but at least you showed me the headache I was undertaking. Petros is right AC makes it more difficult!!

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Re: Replace Heater Core

Post by grouchytom » Fri Feb 03, 2017 9:55 am

Thanks for the write up really helped. Petros is right AC makes it more difficult. Still sucked but now have heat mama is happy so guess it was worth the headache. Thanks again!

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Re: Replace Heater Core

Post by Petros » Tue Jan 08, 2019 7:35 pm

I am just getting my daily driver back together (with a rebuilt engine), including replacing the heater core. I also took out the whole dash to repair it (my tercel was stolen a few years ago, when I got it back, missing my tool bag, the battery and a few other items), the thief tried to help himself to my inclinometer by pulling on it hard, and only succeeded in bending the mounts and pulling the forward edge of the padded dash off (breaking some of the plastic clips). So I pulled it all apart to fix the bent/damaged dash mounts.

something else I discovered, there is NO section in the FSM for replacing the heater core!!! how could they leave that out?

They do have one for replacing the dash pad (not very detailed, but it is at least there). It has been several months since I pulled my dash apart, now I can not seem to remember how/in what order, all the detail pieces go back into it. I am afraid I will get it mostly back together and discover a strut or duct than can only go into place with the dash off of it. This thread, with the pictures is useful, but it does not go into removing the whole dash.

So much important information missing from the FSM. they also have odd names for the parts, they call the dash board a "pad".
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