No Heat - Let beat a dead horse

[TyzToyz]

OK, I've done alot of research and troubleshooting, but cannot figure this thing out.
1990 Corolla GTS, 4AGE EFI, 5 spd
Engine gets up to temperature fine (on the gauge), control valve is free and unblocked, flushed the heater core, Toyota OEM thermostat, bled system by jacking up the front end and had the rad cap removed with heat on full until thermostat opened and made a mess on the floor. Topped off system and took it for a drive and again little to no heat. I currently have cardboard in front of the rad and if the car sits and idles, the rad cooling fans come on, but again, very little heat from the vents.
All hoses are hot and the car blows lots of heat if the outside temperature is at or around zero degrees Celsius.
It has been -30 for the last 3 days and I have been driving around freezing.
Please help!!!!!

Tye

[eberbs1]

weak water pump maybe?

[SuperRA]

Maybe the control cable for the temp lever (heater controls) needs adjustment or has broken? It controls a door which switches between the hot air and cool air. It may be that the door is stuck midway or something.

[nevada]

Originally Posted by eberbs1

weak water pump maybe?

i recently worked on a mazda where the fins on the WP had literally corroded off. so this is definately a possibility.
altho, this car was also overheating badly.

Originally Posted by SuperRA

Maybe the control cable for the temp lever (heater controls) needs adjustment or has broken? It controls a door which switches between the hot air and cool air. It may be that the door is stuck midway or something.

i would check for this.
make sure the blend door is working correctly.

you may need someone to help, unless you can lay under the dash, AND work the controls.
you need to switch from hot to cold, while watching underneath. verify the cable is still attached, and that the lever for the blend door is making its full travel.

[TyzToyz]

Thanks for the replies!
So let me get this right. The "blend door" is connected to the hot/cold (red/blue) lever?????
Is there 2 cables run off of this lever? Does this car have a "blend door" and the control valve that is bolted to the fire wall just before the heater core?
The blue cable connected to the hot/cold lever that goes to the valve on the firewall is moving freely and operating properly.

ALL hoses are hot including the 2 heater core hoses and the lower rad hose, so I can only assume that the pump is flowing. Plus, when I bled the system and the thermostat opened, I could see the liquid flowing.
This has got me extremely stumped and frozen.
Any other suggestions or experiences?

Tye

[nevada]

Originally Posted by TyzToyz

Thanks for the replies!
So let me get this right. The "blend door" is connected to the hot/cold (red/blue) lever?????
Is there 2 cables run off of this lever? Does this car have a "blend door" and the control valve that is bolted to the fire wall just before the heater core?
The blue cable connected to the hot/cold lever that goes to the valve on the firewall is moving freely and operating properly.

ALL hoses are hot including the 2 heater core hoses and the lower rad hose, so I can only assume that the pump is flowing. Plus, when I bled the system and the thermostat opened, I could see the liquid flowing.
This has got me extremely stumped and frozen.
Any other suggestions or experiences?

Tye

yes, there will be 2 cables, one for the flow control valve, and one for the blend door.

i see this problem quite often, on different vehicles, it usually ends up being an issue with the blend door. sometimes the cable pops off, sometimes the sheath slips, so the cable isnt throwing the door as far as it should...or some other issue.

[90 GP]

It sounds like you have covered all the bases.The heater core is probably not too large to begin with and factoring the extreme outdoor temp it is probably working as well as can be expected . If it didn't work well at zero degrees I would troubleshoot it further.

[toyotaspeed90]

there's multiple things that it could be....

clogged heater core
the heater valve (engine bay) isn't moving
the door that leads from the heater core to the vents isn't opening

Check all of these things.... for the 2nd two.... anytime you move the arm from cold to hot it should move both the heater control valve and open the door between the heater core & the vents.... it's possible that either cable is either not connected, broke, or there's a problem with the slider itself so the cables aren't moving.