Broken AC. Now what?

[Rusty Nail]

You're a good sport Old Boy! Have a seat.


You will be interested in removal wiper cowl. This may prove tricky and you might nerds a proper tool. I'm afraid it's removal will/may be necessary to complete the repair with the best success.
Here we teeter on the A/C system beginnings as the vacuum door underneath the cowl controls the "vent" and "max AC" functions, allowing or denying fresh air or modernly called "re circulate" recirc function. Outside fresh or inside cabin, conditionrd air.

Probably have to take the cowl off to play with the vacuum pod and lines which control the operation from behind the AC controller.
This involves removing the wiper arms and is likely the most strenuous area of the rebuild.

Lucky for you the vacuum hoses have color coded track lines on them. Orange to orange, green to green, etc. It's easy.
Theres red and yellow...and you get it.
To ensure proper HEAT function, the door underneath the wiper cowl must be closed when the controller is slid to the hot side WHICH, in kind, operates the BLEND door, that your P.O. (previous owner) has forced to cool with that @Rusty Nail because when you remove the pin from the TEMP door, it stays half open - as you have witnessed.
Three doors I think is right.

They obviously were trying tobeliminate the residual heat from the cab but were doing it wrong. Instead of stopping water flow to the heater core, they went Neanderthal on your heater box and now you must repair it to re-establish that lost value to your truck's worth.

Gettin on winter and heater/defroster is priority. You can remove the homemade block off and see what's in there. Clean it real good so it won't blow stink later.


I have to do work. Hold on ill be back.
The #10s in the pic are little foamy gasket type deals that you have to buy - or make?

 

[Rusty Nail]

Well, kinda bad news but it's nothing you cant fix. See the dashpad is missing. It holds the vents.
Youre gonna end up with most of your air blowing behind the center of that metal "dashboard". Its alright cuz that makes you less work right now. and you'll be in it MAYBE $100 US to get heater and defroster using what you already have.

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The big hole on the right requires a flexible duct and vent and seal and director valve thingy. Most of that air will blow non-directed out of the heater box and it WILL heat the cab interior - eventually.. Look and find the abolute round exit 2&3/4 hole. You can find a piece of tube to connect there with a zip tie or two and hang it out of the passenger hole. It will be fine and that's your solution there -cheap and easy. Think clothes dryer ducting. Maybe it's 2&7/8.

I guess the same could be done in place of the previously mentioned unicorn part of ducting under the steering column thats hard to find, but it will require three times as much dryer vent to hang out of the big hole by the instrument cluster. Again, that's your little money fix.* except that connects to a square at the box.

The big hole in the middle center requires nothing to feed air to the center of the seat...ahh ! Thats the square hole in the middle part.


That floor looks fantastic btw im jealous.


Again, im not certain the difference between our trucks I just fixed an 88 but it really doesnt look good for the AC right now. Continue to ignore it. ...it costs a bunch where ever you are im sure. lemme scroll back.

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I am very distracted if this isnt making sense.
The driver vent under the steering column goes to the homemade block off. It's a long way to run dryer vent! The round hole feeds the passenger side and the square hole in center vent towards back seat

All the white ish on the bottom of your heater core is evidence it leaks. You must buy another like the example correct for your application.



Ive got to work. Maybe @gotyourgoat will pick up where I left off. 3am monday morning is pretty busy.

 

[jerula]

I just checked. I've located the vacuum door in the wiper cowl. It wasn't that hard - I just removed the wiper cowl plastic cover

I do have the dashpad - it's just not on the picture. Both ducts are there too. As I mentioned in my previous post. I have all the parts except the ones that I circled out.

Working on getting a new heater core. Parts for these cars can be difficult to find here in Denmark

... and thank you on the floor. I've just finished a complete overhaul. Turned out pretty good I think.

 

[jerula]

Spent most of the day sourcing the missing parts. I found everything but I still miss one very important piece. The one shown here. Does anybody know where I can find one of these?

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[Scott91370]

I am going to guess by the comment in your first post, "I don't know the American names" that you really are in Denmark. I don't know the time/cost to ship there but I think I may have one. I will check this evening.

 

[jerula]

Thank you, Scott. I really appreciate that. Crossing my fingers.

Yes, I live in Denmark, Scandinavia, Europe. Long shipping times don't worry me, usually with express things arrive within a week. For bigger parts that need to sent by ship, it takes anywhere between 4-6 weeks. Patience is a virtue for us European American truck fans

Would you believe it. This morning I was in the garage and one of my kids came out. She stumbled and accidentally hit the table with my dissambled parts. Hitting the defroster duct and breaking off one of the pieces off that hold the assembly. Argh! :|

 

[gotyourgoat]

Good news is it appears most of the items you are missing are gasket type items. Could just cut some yourself out of some locally sourced material. If you can't find some pieces I'll bet there's at least a few people here with ac equipped parts trucks that would be willing to box it up and mail it off to you.

If this was my mess I'd try and source all the bits that go in and on the box. Heater core, ac evaporator, all the flaps and doors. Put the hvac box together completely once and only once. Just leave the caps on the ac components where they exit the box so when or if you decide to make the ac work you aren't doing this all again.


Btw, there shouldn't be a wood screws in a wood bed. Hundreds of nuts, bolts and washers to put it together though.

 

[jerula]

Thank you. I will never need A/C, so it's a waste of money for me.

I am in the process of finding the missing pieces. Right now I just miss that collector duct that connects the heater box with the upper ducts. When I have it all, I will have a go at assembling it.

Today I fired up the truck and I noticed something. The blower runs no matter what I do on the instrument. I have been offered a cheap non-A/C instrument by a friend, but I am not sure if I should take the offer. I am worried the electronics and wiring is different from what I have now.

 

[gotyourgoat]

On the early squares, roundeyes, the fan always ran no matter what when the vehicle was on. Chevy called it cabin ventilation or something I don't remember their term at the moment.

You can just pull the one wire off the blower when you don't need it in the off season. Yours sounds like it is working as it should being a 74. It should speed up from the low constant circulation when you actually turn the fan on though.

 

[jerula]

ah ok. Well, nothing happens when I adjust the fan speed. It just stays at "idle".

 

[jerula]

Finally an update

I got a new heater core from LMC ... appears it does not fit. It's too high. I've contacted them and asked for advice. So, for now - no assembling of the whole thing.

I got the missing piece that connects the heater housing with the ducts. Yaye!

Had a good look at the defroster duct again and decided it is too broken to be reused. Will find another one.

I learned a lot over the past weeks though and it turns out the piece that is blocked at the end of the heater housing is where is supposed to be the defroster valve actuator. Aha. I am thinking that while I am at it, maybe I should replace the air distribution vacuum actuator (may be broken which explains the nail that kept the door locked).
Found this great diagram: https://www.justanswer.com/gm/2o1dx-remove-heater-core-1985-sierra-classis-truck.html ... it looks very similar to what I have and part 21 on the diagram is the one I am missing.
Now, these are really hard to find. I spent most of last night trying to find one, but no luck. Any tips or help?

Finally I need a new control unit.

Hopefully, with a correct heater, 2 new actuators, new defroster duct and a new control unit, I can finally try to re-assemble everything. That pretty much maxes out my budget for this project.

How does my plan sound to you nice people?

.. any help on finding the actuators would be greatly appreciated

 

[jerula]

I just found these: https://www.oldairproducts.com/products/factory-replacement-parts/vacuum-parts

but I have no idea which actuators to pick. Anybody?

 

[jerula]

Update

I sourced all parts except the defroster duct. Installed new heater core. Replaced the air control unit. Replaced broken vaccuum hoses. Bought new actuator for the floor air control. Reinstalled vaccuum from the carburator (that was removed by the previous owner). Everything was reassembled. Everything is now back in stock and seems to work nicely.

Only one thing left and this task is done. When I set the blower to maximum, it stops. Everything else works. It must be something with the blower itself or maybe I am just not using the control unit correctly, but I think I tried all combinations. Or is there a fuse/wire specifically for max speed that I should/could check?

 

[Rusty Nail]

YES.
The hi speed blower is powered via that fuse along your firewall - behind the distributor. The one you always wondered what it did?

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[75gmck25]

There is a separate fuse for high speed. On high position it uses the high speed relay under the hood on the plenum to provide direct power to the fan.

On my ‘75 there is a power wire running across the top of the firewall, from the junction block near the brake booster to the high speed relay on the heater plenum. My truck had an inline 30 amp fuse in that wire and it kept getting hot and burning the plastic holder. I finally spliced in a new blade-type fuse holder and 30 amp fuse, and that has worked since then.

Bruce