AC/ Heater core replacement

[Astro-Balls]

Need to replace the heater core and I suppose now is a good time to replace the AC evaporator at the same time so I can get to the AC system later.

Can the AC evap be cleaned and pressure tested/repaired like a heater core tanks? or just get a new one?

My AC system is not working at this time but since I will have to go through all of the labor to change out the heater core I would be ahead of the game..

Any other parts needed while removing the heater box? suggestions?
Just bought the AIM and will be going over it tonight.

[Already Gone]

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[Bob B.]

Evaporator is aluminum, so fixing it would be tough. Since refrigerant and oil run through it they do not often corrode from the inside. Most common problem I have seen with them is people twisting the inlet and outlet tubes off trying to remove the lines. As with any part that is buried, might not be a bad idea to replace it since you will have to remove the case anyway.

If you have not done the heater core and evaporator in an A/C truck before, easiest way is to remove the right wheel and inner fender. Some of the screws go through both the heater case and evaporator case. Probably a good time to replace the blower resistor and high speed relay too.

[GMC 72 4X4]

You do not have to take the air cond. box off of the engine side of the firewall to change the heater core just take out the glove box, all the fabric hoses( they will likely be so stiff and fragile that you will have to replace them) then unhook all of the bolted together plastic heater and AC vents in the center of the dash.
Unplug the wires and then find all the bolts that hold the cases together, unhook and remove the heater hoses, clamps on engine side of firewall, then the inner case should come off. By the way if your heater fan doesn't work properly on 1st or 2nd setting now would be a good time to replace the heater resistor coils because they are very hard to access unless you have the inner case off.
72 GMC 4x4

[Astro-Balls]

Originally Posted by GMC 72 4X4

You do not have to take the air cond. box off of the engine side of the firewall to change the heater core just take out the glove box, all the fabric hoses( they will likely be so stiff and fragile that you will have to replace them) then unhook all of the bolted together plastic heater and AC vents in the center of the dash.
Unplug the wires and then find all the bolts that hold the cases together, unhook and remove the heater hoses, clamps on engine side of firewall, then the inner case should come off. By the way if your heater fan doesn't work properly on 1st or 2nd setting now would be a good time to replace the heater resistor coils because they are very hard to access unless you have the inner case off.
72 GMC 4x4

So to change out the Heater Core there is no need to remove the inner fender? but you do have to remove it to swap out the Evaporator?

My fan switch is not working, could it be that the resistor is shot?

[GMC 72 4X4]

I don't know about changing the evap. When I replaced my heater core I didn't need to break the AC system so I didn't. I was able to get the inner box off without doing anything under the hood except remove the necessary bolts.
GMC 72 4x4

[Hotcorner]

Originally Posted by Astro-Balls

So to change out the Heater Core there is no need to remove the inner fender? but you do have to remove it to swap out the Evaporator?

My fan switch is not working, could it be that the resistor is shot?

There are studs for the inner box that pass through the fire wall. Inner fender needs to come off to access the bottom nuts on the studs passing through the firewall.

[GMC 72 4X4]

Sorry I didn't see about your heater fan not working that's a whole different issue. First make sure you have power to the switch then try the blower speed on high that will bypass the blower resistor if it works on high but 1 or 2 your blower resistor is bad. If wont work at all then either the fuse is blown or the power wire is unhooked between the fuse panel and the blower speed switch

[Astro-Balls]

OK, Thats what I thought, thanks.

[BCOWANWHEELS]

its a BUGGER of a job

[Astro-Balls]

Yes, bugger of a job but somebody has to do it and that somebody is Lucky Me..
so Ive ordered

Heater core
Hoses
Gasket set for plenum
Fan switch for heater AC
Blower resistor

Anything else before I tear into this truck?

[vitamin_c95]

Thank you for posting this. I will be doing my heater core soon as well (on back order) and I never saw the resistor idea when searching the forum. And thank you to the ones who replied

[BCOWANWHEELS]

The inner fender well has to come out a/c or not

[vitamin_c95]

From what I have searched on the forum, taking out the inner fender will make the job easier so you can reach the bolts on bottom of the airbox. I have also read the correct combination of extensions/universal can reach it as well, without pulling the liner. Pick you poison I guess. I'm going to pull the liner when I do it

[Astro-Balls]

So is the original size of the AC heater core 2 1/2" ? replacements I'm seeing are 2"..

[vitamin_c95]

Correct. Many have used the 2 inch, but it fits different. Can't remember what needs to be done. I havnt searched that far.

[Astro-Balls]

Does anyone sell a 2 1/2" core?

[vitamin_c95]

Check the classic trucks parts sites (brothers, classic truck etc). The brothers one is on back order.

[Astro-Balls]

I'm only finding 2"

[vitamin_c95]

Where are you looking? Just curious. I am thumbing thru my physical catalogs and will report back. Also, how much you looking to pay?

[randy500]

Try to find a copper heater core. I bought one about 1.5 years ago, I think from advance auto parts, tyrnrockauto too, it was a real good fit.

For the evaporator, you can flush it on the truck, but you will probably want to remove he engine side box to clean it out completely, usually full of debris between the hot-cold valve and the evaporator.
Flush with acetone, pour it in and push it out with air pressure. Remove the poa valve and the oil line that goes to the poa valve before flushing, flush till it comes out clear, I put a hose on the exit and run it into a bucket to see the flush results.
There is a schrader valve under the oil Line in the poa valve, it’s a special low pressure one, most people recommend not removing it. They are available but Kind of hard to source.

[vitamin_c95]

I sure as he'll can't find any 2.5 inch ones either.

[Astro-Balls]

I cant find a 2 1/2" either..
As far as pricing I see Copper Brass cores anywhere from 39.99 up to 149.99 some are the same part made by APDI.

[Astro-Balls]

Heater Core HE double Hockey sticks..

Ordered one from Brothers, Out of stock,

Ordered one from a Vendor on Ebay (AutoGeek).. said it was Brass/ Copper but when it showed up it was aluminum..

Ordered from another vendor on Ebay (Advanced Auto Parts) Said they had the Brass/Copper core, showed up and it was aluminum..

Who has a Fricken Copper Brass Core??

[vitamin_c95]

Yeah I ordered from brothers too. But pissed because they already charged me (3 weeks ago) even tho they said I don't be charged until it ships.