No Heat / Luke warm inside cab

[Buzzard67]

Hello everyone.
I own a 1984 Toyota Tercel DXL and have problems with Luke warm heat in the interior of the cab. I tell you what I know and what I have done to trouble shoot this problem.
1) Adjusted Heat control cable next to fire wall. (closes and opens good)
2) Professional radiator flush and fill at the Jiffy Lube.
3 )Replaced Radiator cap.
4) Opened up dash and checked all cables and vent doors everything is opening and closing.
The car runs great and I have a "Temp gauge" on the inside. Car runs at normal operating Temp(no fluctuation).
All the heater hoses are hot to touch, upper and lower hoses feel the same.

Q: Could all this be a simple as a New Thermostat? According to the "Temp gauge" its running normal, needle just shows its running 1/4 of the full gauge.
I would open to any suggestions. Iam not a mechanic, but can do small projects.

Thanks in advance

[irowiki]

So if you set it to "Cold" it is cool, and if you set it to Warm/Hot (on the dash) it is lukewarm?

How is the airflow? Sounds like a possible plugged heater core, or maybe the thermostat is stuck open.

The thermostat is an easy fix, I managed to replace mine as well with little past experience! The heater core, not so much, I think you have to take the entire dash apart to get it out.

[xirdneh]

For the control valve on the fire wall
it may open and close ok but make sure the cable is opening it all the way
unsnap the cable and push control lever towards the driver side as far as it will go and re-snap cable

[Buzzard67]

To: Irowiki
Yes, set it to cold it get cold, set it to hot Luke warm.
Is there a diagram on this site wear the Thermostat is ?
Hope its not the heater core.
One more thing, it dose not leak any antifreeze.

[irowiki]

Follow your lower radiator hose to the engine block, where it meets will be a cover with two bolts holding it on, the thermostat is inside there.

[Petros]

if your temp is normal and you get little heat, and the valves and hoses are all good, than likely the core is scaled up with deposits. You might also remove the inlet ducts under the dash behind the glove box and make sure there are no rodent nests blocking the airflow. If that is not it, than you have to fix the heater core. this happens from using tap water with lots of minerals in it for your radiator, I have seen it a number of times, and water with minerals in it is a very bad idea to put in the coolant.

The best way to fix it to replace it, but that is a big job (the whole dash has to come apart). You might be able to just flush the heater core in place, it is easy and you can do it yourself. remove the heater hoses (plug them so you do not loose the coolant), and drain the heater core coolant (save it too). fill the heater core with vinegar and let it sit for several hours. connect your hose and back flush it all out. I like running the outflush via a hose into a large bucket to see what I get out. If you get large flakes and other crap, than likely to fixed it. flush all of the acid and old water out, drain it and than connect the hoses and top up the coolant. give it a try.

A warning, if your heater core is corroded and marginal this could cause it to leak. Not a big loss since it was ready to blow anyway, but you can temp fix it with radiator stop leak and use it until you can get another heater core and replace it.

good luck.

[Buzzard67]

I am going to buy a Prestone radiator flush kit. Do I put the "T" tube for the back flush on the heater hose that connects to the heater control valve, or the one below it ? Both heater hose go into the fire wall. Then I will flush the system and change the thermostat and upper, lower radiator hose and radiator cap.
One other note as I trouble shoot this problem. When I turn the bottom heat on(full right) and turn the upper lever all the way to the left (full Vent), it blows hot. However if I change it to "Bi level or Def its Luke warm or out side temp. I am so in the dark with this problem. This seam like Iam chasing my tail.
One more thing the lower radiator hose is warm, not hot after a day of driving, but the upper radiator hose hot as hell.
Anybody throw some light on this .
Thank you.

[marlinh]

Maybe you have one of the doors not moving correctly. Do you feel that you have to force the lever to certain positions? I had problems with insufficient heat in one of my cars. I replaced the cable assembly ( it was difficult to move) and had great heat in the cab afterwards.

It is normal for the lower rad hose to be warm. That is coolant traveling back to the block after going through the rad. It should be cooler than the upper hose.

[Buzzard67]

It feels like all the interior levers are moving correctly. However the defrost setting blows hard on the driver side and in the middle but passenger side very weak if just a trickle. Out of all the setting the "Bi level and Defrost" blow Luke warm on the hot setting, but the vent setting(bottom lever all the way to the left is blowing very hot. Which could be good news that it could not be the heater core.
Question I am going to do a home radiator flush and back flush from Prestone. Due I put the "T" on the heater hose with the heater control valve or the lower harder to reach valve.
I cant stress this enough , I am GOING CRAZY. (see above)

[marlinh]

If you are getting good heat in at least one setting, it is most likely not the heater core. One of those doors isn't moving properly, maybe some ducting is out of place or plugged. You need to get under the dash and check all the linkages.

[dlb]

If you are getting good heat in at least one setting, it is most likely not the heater core. One of those doors isn't moving properly, maybe some ducting is out of place or plugged. You need to get under the dash and check all the linkages.

i think marlinh hit it on the head. take a look underneath and make sure that all the black plastic ducting is securely connected. i have driven tercs with part of the dash and ducting removed and wondered why i wasn't getting air in certain places. took me a few minutes before i realized half the stuff wasn't there.

[Buzzard67]

Thank you everyone for the great advise. Today is the day I tackle the radiator flush(back flush), change thermostat and upper and lower radiator hoses.
Now when I am done with that project,I will look under the dash. Is there any diagrams of what I should be looking for on this site? Can I get at this duct work by just removing the glove box or do I need to remove the center dash (where the climate controls and radio are)? Is there any cables under drivers side ? When I am under the dash I will check all the cables and doors to see if everything is opening and closing tight. If any one has pictures or diagrams that would be great (not a mechanic).
I still cant get my head around why it blows hot out of the vent setting, but not on Bi-Level or Defrost. Dont get me wrong I love this car and if I had the opportunity to buy another I would in a heart beat.
Every time I take it out people stop and tell me there stories, they had one and loved it, wish they never sold it, and multiple offers to buy it five offers in one year.
So please help me to over come this crazy problem.
I will send more pictures when (if) the sun comes out.
Later

[marlinh]

You can remove the glove box, and the panel under the steering wheel to see all the cables. You do not need to remove the center dash, just the cover for the radio, only 4 screws. What you may want to do if you can't determine if the doors are moving properly is carefully disconnect the cables individually and move each door independently and see if flow or heat level increases. The duct for the right defrost is above the white plenum between the fan motor and the center dash. I can't remember how hard it is to see. I hope this helps.

[dlb]

buzzard, look at the last two pics in my post here.

https://tercel4wd.com/forums/viewtopic.php?f=7&t=7617

those black plastic duct pieces are what we're talking about. on the passenger side, you must remove the glove box. on the driver side, you must remove the trim piece below the steering wheel. you just want to make sure that everything is securely connected and not missing.

the cables that go from the control levers to the various flaps and valves can be a little tricky to see and access but once you have the glove box and driver side lower trim off, you can look up behind the climate controls and can see each of the cables coming out. follow them to their destination points and make sure they are all securely attached, that none of the plastic arms they attach to are broken, and that the target points seem to open and close fully. the last one can be tough to tell but if it's not obviously messed up, it's probably fine.