Replaced heater valve and cable, now no heat?

Have you verified that the coolant is actually reaching normal temperatures above 180°F with an OBD scanner? That is, you don't have a stuck open thermostat?

 

My Ultra Gauge is still showing my temp from 192-195, but I’m unsure if it’s drawing directly from the coolant temp

 

Everything back together once again, still close to the same result. Replaced the heater core just to be on the safe side since everything was apart (not needed, I know but just on the side of caution). Parked on a steep incline to burp the system this time and did get some air to escape. Driver vent will blow decently warm air, barely anything through the middle vents (even on cool), and the passenger side is still blowing luke warm/cool air...which makes no sense. The in and out hoses from the core are hot. I don't know what else to look for or even a cause. Only other thing I could see wrong is that the foam on the various doors in the 'heater assembly' have deteriorated. I did add some small, thin weather stripping foam around the edges of two of them I could reach, whether or not its made a difference I'm not sure.

The cause for the passenger floor being wet does look like it would be from the evap drain. There was a slight watery film on the inside of the cab where the hose meets the evap..I'll look into that later.

 

Well damn. Whole lotta work and was hoping to hear a different report from ya man.
Something thing I've done in the past that might be worthwhile for you is to stick a longer piece of painters tape vertically on the overflow reservoir. Keep a magic marker in the truck and after each time you turn the truck off, open the hood and make a mark on the tape at how full the coolant shows. Then next morning see how the level is dropped, that's the coolant that's replacing the air as it works itself out of system. Sorry if you already knew this stuff, not trying to be redundant

 

Is it possible to somehow physically reach the heater core to touch it and see if it's getting hot 180F+? It would be good to know if it's the heater core not getting hot or the air not being 100% directed through the heater core.

 

I know, me too. I was hoping to at least find something to blame in the heater assembly with all the doors. I’m going to check tomorrow and make sure the blend doors are going through the full range of motion.

I’ll try that with the tape, I’ve never done or thought about that before. Thanks!

Unfortunately not. Not other than the inlet and outlet under the hood, there’s no way to physically touch it.

The air not being 100% directed through the core is a good possibility by looking at how the doors are sealing now that most of the foam has deteriorated. There was also a section inside of the heater assembly that I couldn’t tell if it was broken, or if it was designed to be that way.

earlier this ear I found a bunch of trash in the fan, I’m going to take the fan back out tomorrow and see if something else isn’t trapped inside and hindering the air flow

 

This last paragraph, oh so you've had to get in there before and found crap in there? In the ducting? It sounds like more crap could be a possibility, with the less air coming out at certain vents. I'm still wondering how the hell the core isn't getting hot......
Do you have an outside air intrusion somewhere getting into the ducting for the vents? I dunno how but it could be like a vac leak and as the fan blows it could be losing volume through openings, stuck doors or whatever they're called.
Did the heat work properly at one time since you've owned it?

 

There was stuff that had gotten caught in the fan a few months ago, caused a terrible racket so I removed the fan and removed the junk out of the fan. I assume it got in when I set it on fresh air because 98% of the time I leave it on recirculating. All the ducting from the heater assembly to the vents appeared to be free and clear. I should have checked where the evap assembly and the heater assembly meet and I forgot. The core seems to be getting hot...the inlet and outlet lines are hot, so surely it is. Especially with it being brand new. The driver vent gets warms, but passenger side is blowing luke warm/cool...and I still cant understand why the middle vents are barely blowing. Theres nothing blocking the vents or the door.

A outside intrusion down the line closer to the fan is the only thing I can think of that might be hindering it. If the fan isn't blowing through the evap and core properly, or hard enough, it could cause an issue?

The heat has always worked great ever since I've owned the truck for the past 12 years, its perplexing and frustrating to say the least.

 

Gotcha gotcha. Certainly is a different kind of problem. I believe how you indicate that it doesn't blow well out of the center vents will have much to do with taking care of the heat issue as well.

 

If the evaporator is clogged with dust and trash, would that cause an issue with the fan not blowing properly? There by not forcing enough air over the core and a lack of heat? And possibly explaining the lack of flow from the middle vents? The AC seems to blow cold, so maybe not....

 

Yeah crap in there can affect air flow and the heating and the cooling of the air.

 

Took the evaporator out today. Pretty nasty! Nasty enough to cause lack of flow and lack of heat? That's the question. I cleaned the evap with coil cleaner, appears to have gotten the vast majority of the junk out. I'm going to go over it one more time tomorrow just for good measure.


Also took the entire fan assembly out to see if there was any obstructions, everything appears to be free and clear from the cowl down into the assembly. I can't see all the way into the cowl to see exactly where it pulls the air from. Is there a clear opening for the intake from the top if I were to take the cowl off?

And lastly, I made sure the blend doors are moving as they should now that the heater assembly is back in the truck, everything moves as it should. With the evap and fan out of the way I was able to move the temperature control and watch the doors move. With everything out of the way and a clear shot to the heater core, Would it be safe to run the truck to see if the heater core is getting hot with the evap out of the truck?

Earlier in the thread I mentioned there was a piece inside of the heater assembly that I could not tell if it had some how broken, or if it were designed that way. Below is a picture of inside the assembly, looking at it from the side where air would enter from the evap. To the right is one of the doors that directs air through the heater core, to the left cool air would flow. Circled in red is the questionable area. Just on the other side is the door that goes to the feet position, and the door that controls the face position. I didn't find any pieces in the assembly, but I have had a small portion of the duct out before...perhaps it fell out. Part of it towards the bottom looks like it may have some how broken, but part of it appears to smooth like it was designed that way. Which to me, doesn't make a lot of sense....but I'm just a amateur mechanic, not an engineer at Toyota haha!

 

Wow! That's really digging into it! Definitely being all blocked off in there will hinder the air flow, so this was awesome that you pulled it and got eyes on it. These might be the best pics of this part of the dash and hvac system I've seen! So these pics are a good resource for the forum too. I've never seen in there on the taco so it definitely helps me visualize what you're explaining.
I can't tell about that 'cracked' piece you're saying there circled in red in the pic. It looks like it should be like that, as it looks now. I should look at a diagram so I can see the vent doors and crap better. If you have a link for a diagram post it up, but i'mma go look for a dash/venting diagram on the internets. Gimme a few minutes

 

I should have taken more pictures while I was in the heater assembly to show all the doors and kind of how it works. I’ve yet to find any diagram that shows the inner workings, or any good pictures. Perhaps I’m not searching the right key words. So unfortunately I have no links or leads.

The only reason I think it’s a possibility it could be broken somehow is because of the middle vents having very little air flow, in ac or heat. My reasoning for this is because of pressure...the system is putting out enough pressure to reach the end of the line, the driver and passenger sides, but not enough to fill the middle, because that ‘missing’ section would allow airflow to be somewhat redirected and not build enough pressure. Does that make sense? I’m not sure I would be entirely right on that theory or not.

Would it hurt anything to run the truck up to temperature to check that the heater core is getting up to temperature even though the evap is disconnected? Just to rule that out

 

You can run the engine with the evaporator core out. The AC compressor shouldn't turn on with zero freon pressure even if you tried to turn it on. I can't think of any other reason why it would be a problem.

 

If there is a piece of the duct/vent missing it can definitely affect the air not being routed properly. I couldn't find any diagrams or anything that was really good enough for me to give any decent suggestions with. But as DocZ stated yes you can run it up to temp. If that heat core gets hot, like it's looking, than looks like you have it narrowed down to the air itself. Sweet man! I'm glad you kept at it and didn't just drop the repair being that it's getting to be a pain in the ass for ya. These are the fun repairs, lots of new thinking and brainstorming, etc and you were nice enough to share it all with us

 

I’m going to do some more digging, surely there’s a picture or video somewhere that I can catch a glimpse inside the heater assembly to check.

It’s been a fun journey so to say the least but now that I’ve completely disassembled every part of the AC/HVAC and duct work, I’ve come to realize it’s actually a very simple design. Not near as complex as I always thought it might be. Just wish I would have taken more pictures. I plan on posting some more later on now that I can see where the system intakes the air from. Hopefully to help someone else down the line.

 

Sounds like a solid plan to me hombre

 

After fixing a leaky hose clamp, I was able to burp the system once again and take the truck for a test drive. After driving around for a little while and truck temp between 192-196, hit the heater core with a digital temp gauge and its reading about 170ish. I would assume with would be more than reasonable? Granted, my digital temp meter is a parts store special, but it should be good enough for government work in this case.

Finished cleaning the evaporator and let it fully dry for a day or two, and carefully straightened some of the fins that were badly bent. Much much better now! Will get it all reassembled this afternoon and hope for the best. Because if this doesn't work, I believe Ive exhausted every option.




An after thought after burping the system: How much cooler should the lower radiator hose be from the upper? While idling and getting up to temperature, the upper is warm, while the lower is cold to the touch. This is after the t-stat has appeared to open, about 180 degrees. Would that be normal after waiting for the truck to come up to temp and shortly after the t-stat opening?

 

Somewhat resolved! Reinstalled the much cleaner evaporator today, recharged the AC (cause it's Georgia and it's always needed). Drove it around tonight, heat seems to be working as it should! Good flow out of the driver vent, flow is still weak but a little better out of the middle vents, but the passenger side vent still doesn't seem to be blowing air as hot as the other vents, even though the air flow is good. Why? I have no idea. All the air is coming from the same place, there are no blockages, and everything that was taken apart has been sealed to the best of my ability. The only other conclusion I can think of is perhaps the fan motor has become weak over time and is not pushing out enough air...so by the time is reaches the passenger vent (technically the closest to the fan) the air may have cooled, and could explain why the air out of the middle vents is not like those of the other two. How? I have no idea. But its the only other possibility I can think of.

Now that the debacle it some what resolved, I'm going to do my best to explain the inner workings of the AC/HVAC system for future reference. Should have taken more pictures, but I wanted this pain in the ass over with.

Below is the view up under the cowl, the plastic piece under the windshield wipers. On a first gen there is no cabin air filter. The intake for fresh air is about where the blacker raised potion is, just below the windshield wiper nozzle. It's covered, so viewing the intake from the top is impossible. The second picture is showing the rest of what is under the cowl. So 3 openings that lead into the main intake for the fresh air setting.



From here, the fresh air is fed down into what I would call the 'fan assembly'. The fan assembly is the farthest portion on the passenger side under the dash. It is accessible without removing the dash by removing the glovebox, and then the evaporator assembly. The fan assembly consist of nothing more than the fan at the very bottom (that can be removed by 3 screws without removing the whole assembly) and one door. The door that controls 'recirculate' and 'fresh air'. So, pretty simple.

From here the air is fed through the evaporator assembly. The evaporator assembly consist of nothing more than the evaporator. Granted, there are a few (2-3 I think?) electrical connections that must be undone to remove the assembly, and four screws/bolts. Once the assembly is removed, there are simply 3 clips, 3 screws, and one electrical connection that must be undone to remove the top of the assembly to access the evaporator.

Once past the evaporator we get to the dreaded heater assembly. The cursed heater assembly that Toyota decided to design the truck around. Inside the heater assembly is the heater core, and the doors that control the defrost, face or feat, and the blend doors. There are I believe 5 doors total. Below is a picture looking inside of the assembly looking from the evaporator. The door
to the left controls cool air, the door to the right controls the warm air (heater core is behind this door). There is also a door on the other side of the heater core opposite of this door. As the door in the picture moves to allow air through the heater core, the other door closes. So it moves in the opposite direction, but in sync with the cool air door to the left...if that makes sense. Straight ahead you have the door that controls the feet. Which leaves two doors that cannot be seen, the door to the face setting ( which is on top) and the door to the defrost (which is also on top).


The area circled in red was a questionable are for me. It looks like it could be broken, but the edges look too smooth...like it would be designed this way. The only other resource I found was this video on youtube. https://www.youtube.com/watch?v=QAf5QFtG6TU In this video there was a slight glimpse that I took a screen shot of below. From that slight glimpse (to the left of the door on the edge of the picture), there is an opening that looks identical to the picture that I took..as identical as is can be from the short glimpse I caught. it looks like the heater assembly was designed this way...doesn't make a lot of sense to me, but I guess the designers at Toyota knew what they were doing.


Around my ass to get to my elbow, but the problem is 95% resolved. Perhaps one day I'll get a new fan motor and see if that completely solves the issue of low air output from the middle vents and cooler air from the passenger. For now, the cab is heating and I have other minor things to delve into. Hope my explanation of the AC/HVAC system helps someone in the future! For those that might be experiencing low air flow from the middle vents, I believe I would try removing the evaporator, fan assembly, and cowl to clean before I removed the heater assembly/heater core. It would at least give access to see inside the heater assembly without removing the entire dash.