no heat after installing new heater core and valve?

[deathpunkbaby]

hi y'all, after replacing my heater core and valve, both brand new, in my fj62, i have no heat in the front dash. both hoses, in/out, are hot in the engine bay, the rear heater is hot as hell, and i have just a hint of heat when i turn on the fan, but it quickly dissipates and blows ambient temp. i'm thinking i crossed the cables on the re-installation because i hear a flap opening or shutting when i flip the heat/cool lever, and at the same time, the heater valve is opening and closing as it should. anyone have insight? obviously, i'm gonna have to get back in the dash, just looking for possible causes/solutions to look for. thanks and happy holidays everyone!

 

[mwebfj60]

When you slide the hot/cold lever is this linkage on the bottom of the enclosure moving? Hot should pull in the direction of the arrow. That controls the flap inside that directs air across the heater core.

 

[deathpunkbaby]

i'll check, thanks!

 

[deathpunkbaby]

checked the flap, took off the cable flipped it back and forth to no avail. heater core is too hot to touch, air blowing hard thru all the proper vents, so there's no obstructions, but no heat. i didn't replace all the weatherstripping around the core, but i can't imagine enough air is going around the heater core to not have some heat in the blowing air, but maybe so.

 

[gregnash]

So coolant from the engine is getting into the heater core but nothing is happening at the core... Two pipes that come out of the core in the firewall, think you said both were hot, are hot with at least a 15* temp difference yes?

 

[peterabbitcook]

Is it possible you bungled routing the hose that runs from the neighborhood of the oil cooler into the firewall? I’ve been told 62’s have a transmission cooler; Could that have been a donor/recipient of the wrong hose? Likewise the rear heater hard lines/hoses?

Sounds like you suspect the problem is inside the dash and not the engine bay, but I’m just throwing a couple ideas that come to mind.

 

[Michael Hanson]

HI, If you still have air in the lines you will have little to no heat. Mike

 

[micruz60]

Sounds like it needs a burp?

 

[deathpunkbaby]

it appears after digging in deeper, when i cleaned out the heater system while replacing the core, i did not open the AC box and clean it out, and it's f'n nasty. i cracked it open best i could without taking the dash completely apart, and found it full of bits of leaves and caked on dirt, etc that i'm guessing has made it's way into the new heater core and is plugging it up. looks like i'll be disassembling the dash in the near future.

 

[deathpunkbaby]

i was able to squeeze my hand in and feel the heater core when i cracked the AC box and it's too hot to touch. also i've parked on an incline, used a funnel, several times to make sure i got the air out, and it's been driven for almost a year since the core replacement.

 

[micruz60]

Can you snake a shop vac into the duct to remove the cloggage?
Or use air to blow out the crud from cabin to exterior.

 

[deathpunkbaby]

i'm trying, but i'd hate to bust the lower half of the plastic AC box. gonna try compressed air too. never really needed the heat in central tx, heading to ks for xmas. colder than a gold digger's ass in the arctic up there this next week. lol

 

[Michael Hanson]

Hi, You can use ac coil cleaner, use as directed . I remove the fan motor and spray it in ,let sit and and wash it out. You might have to reapply more than once Mike

 

[CenTXFJ60]

I’m curious about the new heater core in your truck did you install it or was it done by someone else? Reason I ask is I’m fairly certain you have to pull the whole dash out to get the heater core out. At a minimum the whole HVAC plenum would have to come out. If this was the case then the blower fan and evap core area should have been looked into. And usually the dirt and crud is on the blower side of the evap core (I may have it backwards???) as that’s where the fresh air travels in. Either way you can drop both the blower and the ac plenum without removing the dash. Just remove the glove box and you can access all the nuts. May require breaking open your Hi/Lo ac lines at the fire wall. I see your in Austin...I’m just a bit south of you and always glad to take a look to see if I can help diagnose anything. Good luck as its getting pretty cold in our part of the country over the next week . Jim

 

[deathpunkbaby]

i did the work and, yea, i had to pull the dash. on the way home, i taped up the fresh air vents on exterior, located between the hood and the window as there was quite a cold draft coming in under the dash. after that, there was good heat as long as the fan wasn't turned on too high. i'm guessing i just didn't do a good enough job of buttoning up the ducts, etc, and not cleaning the crap out of the AC box and it blowing thru to the heater core, and subsequently, not replacing the foam insulation is allowing too much air to go around the core. gonna use aluminum hvac tape to seal it up when i pull it apart next time lol