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Cars > Crazyfast79TA’s Garage > Blog > Changing My Trans Am Heater Core


Crazyfast79TA’s Profile Photo


M –51
Bovey, Minnesota
United States


Crazyfast79TA’s Blog Posts 1 – 5 of 247

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Changing My Trans Am Heater Core

By Crazyfast79TA

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Well, I know one thing for sure. This ain't no Chevy Monza. Call them junk or econo-crap of whatever you want, but they were fantastically engineered little cars! I could change a heater core in one over my lunch break at work. This piece of crap Trans Am took over an hour just to get the lower heater hose disconnected! Oh "just a hose clamp?" I can hear you say. The inner fender has to come out and the lower fender has to be unbolted, all without scratching the paint. Then to get the diverter chamber out from under the dash was another job in itself! The glove box had to be removed, the console had to come out and then the control cables and vacuum hoses. Oh and thanks to my own cleaver thinking, I had to take the temperature sender out of the cylinder head to get more slack in the capillary tube to try to get more clearance for the chamber box to come out. Then a wrestling match ensued. That darned thing didn't want to part from it's "home". I got it out, and it was clear a new heater core and the diverter box wasn't going back in the way it came out. I tried this way and that way and it just wasn't working. It was getting close to midnight and I knew I had to have it drivable for work in the morning. So I just took the heater core mounted in it part of the box and screwed it to the firewall, hooked up the hoses, and put the temp sender back in the head. I checked all the connections and filled the radiator with antifreeze. I fired it up and ran it to get it heated up. No leaks and had semi-controlled heat in the car. It's rude and crude, but it works for now until I can figure out how to get the diverter box back in. The diverter box itself needs some re-engineering of it's own. Since the air conditioning parts have been removed along with all the under dash ductwork (by a previous owner) the vacuum hoses, motors and doors haven't worked right. I want it to work like it was meant to, air conditioning or no. A previous owner wasn't aware of the proper way to disconnect the vacuum hoses from the control head. Instead of removing the whole cluster as a "plug in" part, he pulled each hose out. The hoses were just hanging under the dash when I got the car. It took me a while to figure out enough to get the heater to sort of function. It still wasn't right.I may use parts of the Monza heater box that I still have or see if I can adapt and modify the Firebird A/C box to work like it. This will be an interesting challenge! I don't need the blend part of the chamber since there is no longer an evaporator in the system. That will eliminate 2 of the "mystery vacuum hoses", one to push the door and the other to pull the door. It would also be a lot easier to work on the box later on if it could be removed in two pieces. I'll figure it out and make it work properly and be effective. I dug the unit out from my Firebird parts car. The hoses and switch head were still intact so I could compare them to the unit in my car. I found pictures online to verify the unit I had was correct. I tried looking at the hoses on mine up under the dash. I had to remove the plug in from the back of the switch head, They were connected, but some of them are no longer needed since I removed the blend door inside the box. I made sure I had the engine vacuum hose hooked up right then I made sure the defroster door control hose was hooked up. I'm not sure if the outside fresh air door works now (or if it ever did since I've owned the car) but that's not really necessary since I have kick panel and dash vents from a car without A/C.
UPDATE 10/13- I finished the heater/defroster box install last night and today. I made tabs on the inside of the back of the box and straps on the front to hold it together in the car. I had it all together and checked out last night, but waited until after church today to install the glove box and console.

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Read comments on this blog post 1 – 4 of 4

vegavairbob’s Profile Photo
Oct 25, 2013 at 1:27 am
The H body cars are unmatched to work on. I replaced the core on my 71 Vega in no time at all. a couple of cover screws and attach two hoses!
classictrendman’s Profile Photo
Oct 22, 2013 at 11:22 pm
For me I simply cancelled it for now on my 1980 Trans Am that I bought a year ago and still working on restoring it in a very slow motion ????
classicfirebird1979’s Profile Photo
Oct 10, 2013 at 9:36 am
Been there done that......twice. Only I just replaced them. The first one took all day the next one about 5 hours. The wheel well has to come out for the best results. Marking all the lines with a description helps also.
alwaysakid’s Profile Photo
Oct 9, 2013 at 3:26 pm
I ran into the same problems on a '77 Buick Skylark, having to dismantle half the car just to get to the heater core. Had to remove the brake booster and air conditioning, too, I don't think you mentioned that. What were those GM engineers thinking back then!?!

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Cars > Crazyfast79TA’s Garage > Blog > Changing My Trans Am Heater Core

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