Heater Core how to

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Soundmound

Supporting Member
Supporting Member
Joined
Feb 15, 2022
Posts
1,809
Reaction score
5,467
Location
North Central Washington
First Name
Dave
Truck Year
1984
Truck Model
Scottsdale
Engine Size
305
Do you have the part# you ordered? I've ordered two from Napa and neither is correct. Both have been a 1/4" too long due to the end being pointed not chamfered. Keeps the case from closing all the way...
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Do you have the part# you ordered? I've ordered two from Napa and neither is correct. Both have been a 1/4" too long due to the end being pointed not chamfered. Keeps the case from closing all the way...
Yup, And let me tell you the aftermarkets and the OE are NOT identical! Kind of ticks me off. I'm sure that going from copper to aluminum they probably had to be changed a little to keep them strong but gee. The one I used the issue was that it's width was a tiny bit narrower so I had to seal that space off so it would work correctly.

Since I'm logged into the Napa site, if anyone is curious I replaced my fan and used part #BK 6552407
For the heater core I used Napa Part #: TEM 554552

I had no issues getting the case closed back up with that unit. If you tried that part # already maybe it was mis-boxed?
 

Soundmound

Supporting Member
Supporting Member
Joined
Feb 15, 2022
Posts
1,809
Reaction score
5,467
Location
North Central Washington
First Name
Dave
Truck Year
1984
Truck Model
Scottsdale
Engine Size
305
Yup tried all the Napa parts, and O'Reilly and Autozone. All were the same with the pointed base. Mine is basically flat with a chamfer to sit flush to the box. It was out at least 1/4" and I didn't want to force it or modify the core. Looks like I'll check summit as they sell a brass unit and that should be OE style.
 

Soundmound

Supporting Member
Supporting Member
Joined
Feb 15, 2022
Posts
1,809
Reaction score
5,467
Location
North Central Washington
First Name
Dave
Truck Year
1984
Truck Model
Scottsdale
Engine Size
305
Summit was the winner. Brass OE fit, no air gaps. But now of course I have an issue, I think...
You must be registered for see images attach

You must be registered for see images attach

HVAC off.
You must be registered for see images attach

Defrost on. Should this not be closed all the way?
You must be registered for see images attach
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
@Soundmound Which blend door are we looking at? To be honest with you I'm not the best with blend doors unless they are in front of me and I can move stuff and see how it is working. But I will add this, if you marked all of the rods and such when you disconnected things and it worked before you took it apart it's probably fine.
 

Soundmound

Supporting Member
Supporting Member
Joined
Feb 15, 2022
Posts
1,809
Reaction score
5,467
Location
North Central Washington
First Name
Dave
Truck Year
1984
Truck Model
Scottsdale
Engine Size
305
@Soundmound Which blend door are we looking at? To be honest with you I'm not the best with blend doors unless they are in front of me and I can move stuff and see how it is working. But I will add this, if you marked all of the rods and such when you disconnected things and it worked before you took it apart it's probably fine.
Well, I did mark everything and put it back as it was. However, I did not check function before disassembly because the control head was out and had not been replaced. I installed the new one during reassembly. Fan didn't kick on very strong either, I have to diagnose that still. Hot cold slider works great and I can hear the door reposition. The vacuum actuated door shown moves full swing in only one direction, inward.

I tried to justify it as moving some air to the side vents but it would just come out the center also...

Box had been out before for sure. Two of three studs were bent and one was missing the nut. I really took time doing it to make sure it was right, but the gap between disassembly and add on parts arrival was probably a factor too. Plus AC needs charged and core isn't plumbed yet. I just wanted to do it before carpet and seat go back in so it was easier.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Well, I did mark everything and put it back as it was. However, I did not check function before disassembly because the control head was out and had not been replaced. I installed the new one during reassembly. Fan didn't kick on very strong either, I have to diagnose that still. Hot cold slider works great and I can hear the door reposition. The vacuum actuated door shown moves full swing in only one direction, inward.

I tried to justify it as moving some air to the side vents but it would just come out the center also...

Box had been out before for sure. Two of three studs were bent and one was missing the nut. I really took time doing it to make sure it was right, but the gap between disassembly and add on parts arrival was probably a factor too. Plus AC needs charged and core isn't plumbed yet. I just wanted to do it before carpet and seat go back in so it was easier.
We I hope someone better with blend doors than me chimes in. One of the problem is blend door issues are so rare on these trucks I haven't had to do much. Like I said if it was in front of me I'd fart around with it until it was right, but it's hard for me to advise you. What I can advise you on is the fan. low, low-med, med-hi, all have small changes in speed between them, and then hi is much higher than med-hi that's totally normal. If your not getting good air flow on any position, at any speed then I'd replace the fan, often times they just don't turn as fast after all these years.
 

gmbellew

Full Access Member
Joined
May 27, 2018
Posts
1,215
Reaction score
1,283
Location
Kansas city
First Name
glen
Truck Year
1990
Truck Model
suburban 1500
Engine Size
350
do all the settings work properly? what is shown looks like "bi-level" setting. make sure the vacuum lines haven't been swapped around on the main control unit.
 

Soundmound

Supporting Member
Supporting Member
Joined
Feb 15, 2022
Posts
1,809
Reaction score
5,467
Location
North Central Washington
First Name
Dave
Truck Year
1984
Truck Model
Scottsdale
Engine Size
305
Ok checked vacuum lines and they did nothing at all when reversed. I've discovered that when the control head is off I get complete closure which is probably correct? My assumption is the partial opening is to pull dry inside air for defrosting. Any vent selection I choose seems to ride in that position of partially open. Is the control head vacuum harness supposed to hiss all the time or do I have another issue?
 

Soundmound

Supporting Member
Supporting Member
Joined
Feb 15, 2022
Posts
1,809
Reaction score
5,467
Location
North Central Washington
First Name
Dave
Truck Year
1984
Truck Model
Scottsdale
Engine Size
305
Well, found the hiss.... anyone know where to source these parts?
You must be registered for see images attach
 

Soundmound

Supporting Member
Supporting Member
Joined
Feb 15, 2022
Posts
1,809
Reaction score
5,467
Location
North Central Washington
First Name
Dave
Truck Year
1984
Truck Model
Scottsdale
Engine Size
305
I believe LMC HASC em
Have been unable to locate on LMC. I found the OE part number 15-71220 but no one has it.

Anybody have one in a parts rig they'd part with? I just need the rubber bit really, the assembly seems OK.
 

squaredeal91

Full Access Member
Joined
Mar 10, 2023
Posts
2,538
Reaction score
4,586
Location
Cave junction Oregon
First Name
Greg bush
Truck Year
1991 SB
Truck Model
K30
Engine Size
5.9 Cummins 12 valve
Found this on ebay
Item # 266342113866
 

Attachments

  • Screenshot_20230917_191424_eBay.jpg
    Screenshot_20230917_191424_eBay.jpg
    68.1 KB · Views: 44

Forum statistics

Threads
44,173
Posts
950,876
Members
36,291
Latest member
tannerscarber
Top