Swapping A/C box for heat only question...

[Black P-38]

So I located a heat only box from an '83 that I want to buy for my '85. Here's my question...does the outer, (underhood), heater box bolt up to the existing under dash housing?

I did some research and realize the heater cores are different, (I think just the length/shape of the tubes that the heater hoses connect to...). I also searched on here and read about the difference in the plug configuration for the blower speed control.

When I talked to the salvage yard they asked if I just needed the underhood piece or also the under dash piece and I didn't know.

Thanks for your help!
Mike

[Black P-38]

My thanks to Blazin Jason for answering my questions. Should be a relatively easy swap, removing the fenderwell will help with the removal/installation of the boxes.

Need to get the blower motor/squirrel cage from the donor vehicle and I'll replace the heater core while I'm in there. The heat only core has shorter, more compact tubes than the A/C version so I'll go with that one.

I'll post some pics of the swap when I get it done.

Mike

[draggindime072010]

sounds good man

i gutted everything that anything to do with heat and air out my truck and im sure one day i will wont to get my heat back in it

so your pics will be a help to me

[Black P-38]

I'll get pics before, during and after so that should help. Is your truck not a daily driver? I can't imagine not having heat/defog capability...

Mike

[draggindime072010]

naw its not a daily i have a 2003 altima that i drive daily

but i would like to drive my truck some when its cold out but without heat that would really suck

last year when it was my daily all the heat and air stuff was in it but the air didnt work and the heat just barely did i could see my breath the whole 20 min drive to school lol

[Black P-38]

Yeah I figured... Man that would suck, 20 minutes seems like a long time when you're freezin' your azz off!!! I noticed some cracks in my heater hoses when I pulled the A/C compressor so I'll be putting on new ones. Can't be havin' that put me on the side of the road this Winter...

Mike

[Black P-38]

Today I decided to remove the A/C condensor and blower/evap core box to prepare for the heat box. There's just one bolt you can't access which required removing the fenderwell.

It took me a little less than an hour to drop the fenderwell, pull the heater hoses and the blower box. There are alot of bolts mounting the fenderwell,
(13, I think), and 4 bolts, 3 nuts on the blower box.
I took pictures which I'll post up later.

It would have gone much quicker if I didn't have to mess with the fenderwell.
I didn't completely remove it, just removed all the bolts and dropped it down on the tire.

I don't have the heat only box yet so I bolted the fenderwell back in and made a temp cover to block off the large rectangular opening. I'm hoping the smaller heat box will allow me to get to the one pesky bolt without removing the fenderwell again. If not I may just make an access hole in the fenderwell and install a rubber inspection plug in it. The complete box with the blower and evaporator core weighs 12 lbs. I'll weigh the heat box when I get it for a comparison.

The extended tubes on the A/C specific heater core made it a pain to fully remove the box since they extend through an opening in the boxes flange. The heat only core has the typical short tubes so install should be easy.

The condensor weighs just 6 lbs. So far I'm saving 31 lbs by removing the A/C, plus whatever difference between the 12 lb Evap/blower box and the smaller heat onlybox.

I had to remove the radiator hoses, upper fan shroud, radiator etc to access the condensor. It came out pretty easily and boy is there alot of room now between the grille and radiator!

I also removed the skid plate under the transfer case... 9 lbs with bolts.

Stay tuned,
Mike

[Black P-38]

Here are some pics of the removal process...

Before



Fenderwell down



View from wheel well



The Bitch Bolt



View from below, note how flange captures the heater core tubes...



Bottom studs



Box coming out, note how far out before it clears the tubes...



Wide open space



So this is what you see behind the box...



Inside Evap case...



Hope this helps remove the mystery so you know what to expect...

No more A/C compressor (or P/S pump)



Condensor gone



Just for fun...



I'll post some pics of the heat box going back in this coming week.

Mike
　
　
　
　
　
　
　

[Black P-38]

Had a great day at the wrecking yard yesterday! The weather was supposed to be crap but it turned into a beautiful sunny day. I got the heat box I needed plus a nice set of 3 grab handles with bolts and covers, some dash and headlight bezel Torx screws I was missing, a dash vent I needed, the column access lower dash panel and a nice pair of black factory rear wheelwell trims to match my front ones. The rears were gone when I bought the truck so I was happy to find these.

The heat box removal went well except for the lower stud that spun after I had the nut backed out about half way. I had wire brushed the studs and gave 'em a shot of PB Blaster before I started, went looking for the other pieces I needed but I guess it didn't help. I had to bend the stud back and forth to break it off.

The Bitch bolt is accessible with a firm universal on the heat only box due to more clearance. After a few patient attempts it came right out so I didn't have to drop the fenderwell at the wreckers. I still think I'll use a small hole saw on my fenderwell so I have direct access for the install.

The box is metal and light! The A/C box with evap core and blower is 12 lbs. The heat box with blower is only 5 lbs, (smaller motor and blower wheel), so I saved another 7 lbs for a total loss of 38 lbs. I'm guessing if there had been freon in the system the total weight saved would have been over 40 lbs!

I did a little checking on the wiring and I'm planning to splice 3 wires from my harness to the pigtail I left on the heat box plug for speed control. On my '85 the tan wire is low speed, light blue is mid and orange is high. The wires on the '83 heat box are the same except the low speed is yellow.

I wont be using any relay and I'm setting it up so there is no fan operation 'til you select a fan position. In the straight up position, selecting any function makes the brown wire hot so I have cut it back and insulated it. I also cut back and insulated the green wire that's hot in A/C and Defrost modes as I no longer need it. I noticed the coiled wires in the rheostat block are much lighter gauge than the A/C unit's, probably due to a higher amp draw for the larger A/C motor with bigger blower wheel.

I figure the difference will allow a direct splice to my existing harness without the need for a relay. The power wire to the A/C blower is a much larger gauge. I'll keep an eye on the operating temp of the wires just in case but they should handle it fine.

Pics still to come as I need to sand down the heat box and repaint it before the install. Man is it compact, really cleans up the space!

Mike

[Black P-38]

I swapped the A/C heater core for the heat only unit, not a real fun job but I've seen worse... I also disassembled the heater box and got a good start on sanding it. Hope to get it painted and back in tomorrow, then I'll post some pics.

Mike

[Black P-38]

Here's a link to the core removal info I followed, (for the most part), along with some helpful pics...

http://www.sytyarchives.com/howto/vi...imate_controls

For my '85 I didn't have to remove my tunes, just the trim around it which also requires removal of the lower right screw from the Gauge bezel and loosening of the upper right screw. I removed the courtesy light for clearance too.

The ECU on mine is in a bracket with a clip at the top and two slots at the bottom that the studs on the ECU fit into, secured by two nuts. Once I removed the two wiring plugs, and got the ECU out of the bracket, I pulled it out through the glove box opening.

My '85 required the removal of the right hand lower dash mounting bolt, below the glove box and the center lower dash bolt, (through brace), below the stereo bezel. Once they were out and the core cover screws were removed I had to pull outward on the lower part of the dash enough to gain the little extra clearance to wiggle the core cover down and out.

I was able to access the upper right core clamp screw but only loosened it enough to avoid bending the clamp. I just swung it out of the way enough to clear the core for removal and reinstall, then tightened it back down. It would have been difficult to completely remove that screw and reinstall it "blind".

Extracting the A/C core with it's extended tubes was a bit of a pain but putting the heat only core back was much easier. I'm looking forward to wrapping up this part of my weight removal/underhood cleanup project. The open space and access gained is a big improvement.

Getting to that rear passenger side spark plug on the V8 should be a piece of cake plus it looks like the low profile heat box should clear the valve cover without modification... we shall see.

Mike

[Black P-38]

So, the weather here was crappy on Friday and I had other stuff to do but by late evening I finished sanding the heat box and blower motor. I prepped them and the column access cover, (which was very blue), and got those pieces primed and painted. Today or Sunday when I have time I'll get the heat box and column access cover installed. I need to remove the 4x4 vacuum actuator, and clean the fenderwell before the install of the box and new heater hoses.

I'll post some pics soon,
Mike

[Blazin_Jason]

The non A/C box sure is a lot cleaner. I wouldn't drill the inner fender though for that one bolt. It's not like you should have to remove the cover again. Just drop the inner if need be.

[Black P-38]

Yes, much cleaner and more compact too. The box itself only extends a max of 3 1/2" out from the firewall and tapers down to just about an inch. I got it in and took a few pics, still need to do a little cleanup detail but I'm happy with the results. Thanks again Jason for your help, I ended up dropping the fenderwell again instead of making an access hole.













Flashback...



I still need to splice in the blower wires...

Mike

[Black P-38]

Unfortunately when I applied the final coat of gloss black the temperature in my unheated workshop had dropped enough to cause the paint to satin out.

Oh well, I can fix that when I pull the 2.8 out for the swap.

Mike

[Black P-38]

Blower wires spliced in, everything works like it should.
Today I removed all the front drive components and dropped 112 more pounds so I'm down to 3250, (no fuel or driver). Getting there...

Mike

[Ty.A's82]

Hey, im working on a chissis off rebuild of my already rebuilt truck and I did the same swap when i frist drove it. I was never able to get the wiring right on it though if you could point me to the diagram you used to figure out which goes and which stays I would greatly appreciate it. Thanks man

[Black P-38]

I didn't use a wiring diagram... What I did on my '85 is opened up the black corrugated split loom containing the A/C blower wiring, (connected to the relay on the A/C blower box). Then I identified the low, medium and high speed wires by checking with a volt meter with the key on and by selecting the various fan and function positions.

On my '85 the orange wire is only hot with the fan switch on high, light blue wire only hot on medium, tan wire only hot on low and the brown wire only hot in the fan switch's lowest or off position, (straight up). I don't want the fan to run in that position so I cut and insulated that wire with heat shrink tubing.

I also cut and insulated the green wire which is only hot in any A/C mode or defrost mode. I think the green wire activates the A/C compressor clutch which I have no need for.

The heat only box I bought from the wrecking yard is from an '83. I identified the wires for each fan speed by connecting a ground wire to the box, (which is steel), and used a hot wire jumper lead to test each of the three wires coming from the plug on the box. As it turns out, the high speed is also orange, medium speed is also light blue and low speed is yellow.

All I did is splice the corresponding wires together directly, (without any relay), and my heater fan operates just the way I wanted it to.

Hope that helps,
Mike

[Ty.A's82]

Thanks alot for the info.

[Black P-38]

Glad to help!

Mike