92 FJ80 Heat issue (rear heat works, front heat doesnt) (1 Viewer)

[FJ80Steve]

So my 80 is my fall-winter-spring ride. I deleted the entire A/C system when I did the de-smog because it was all junk, would cost as much as I paid for the truck to replace with all new updated R134 system. That being said, fall is around the corner and its time to get my heat working for the winter.

Ive read all I can find and every thread is about the control valve, so my plan is to do a heater core flush and replace the valve anyway. Fingers crossed, I dont have to replace the core. the rear heat does work, albeit not very well. But it does blow hot(ish) air.

My question lies here: Do the rear and front heat share the same core? If my rear heat works, does that mean I likely just need the valve to get the front working? I have tried disconnecting the cable and moving the valve manually, and it moves freely, but did not solve the issue.

As far as diagnosing the heat issue I know that I should check the coolant level, thermostat, rad cap as well. Im mainly concerned that I will have to replace the core and I do not want to do that job, or pay anyone to do it LOL

My skillset is geared more towards mechanical things, and I live in Mississippi so Ive never had to deal with a heat issue before. Go easy on me if this is a dumb question.

 

[leonard_nemoy]

If I recall correctly the front and rear heaters have separate cores.

My 91 had rear heat and no front heat when I first bought it. I just flushed the front heater core with low pressure from a garden hose multiple times and the front heater slowly got better.

Be careful because the heater core is nla and a pain to change out if you were able to find a replacement. On my 91 I didn't use any chemicals, air, or high pressure of any kind to flush the heater core.

I would drive my 91 and get the coolant warmed up and flowing through the core than park and flush it out with the garden hose from both sides of the core. A bunch of nasty stuff would come out and the front heater would get a little better.

I repeated this process a few times about once a week and each time more crap would come out of the heater core and the heat would improve.

I think I flushed it this way 4 times and on the 4th flush nothing came out. The heater worked great for 5 years after this and the core never leaked.

Goodluck

 

[FJ80Steve]

If I recall correctly the front and rear heaters have separate cores.

My 91 had rear heat and no front heat when I first bought it. I just flushed the front heater core with low pressure from a garden hose multiple times and the front heater slowly got better.

Be careful because the heater core is nla and a pain to change out if you were able to find a replacement. On my 91 I didn't use any chemicals, air, or high pressure of any kind to flush the heater core.

I would drive my 91 and get the coolant warmed up and flowing through the core than park and flush it out with the garden hose from both sides of the core. A bunch of nasty stuff would come out and the front heater would get a little better.

I repeated this process a few times about once a week and each time more crap would come out of the heater core and the heat would improve.

I think I flushed it this way 4 times and on the 4th flush nothing came out. The heater worked great for 5 years after this and the core never leaked.

Goodluck

This is exactly what I plan to do. Just didnt know if they were seperate. Thanks for the info!!

 

[ppc]

Each heater has its own core but the coolant flow for both passes through the one and only heater control valve. No heat from the front heater could be a blocked/restricted core, an air pocket inside the core/piping or a problem with the control of the blend door inside the heater box.

 

[FJ80Steve]

Each heater has its own core but the coolant flow for both passes through the one and only heater control valve. No heat from the front heater could be a blocked/restricted core, an air pocket inside the core/piping or a problem with the control of the blend door inside the heater box.

Hmmmm now that you said that, the slider on the control panel (beside the radio) has some weirdness to it. like its bound up. Ill look into that as well. Thanks for the response

 

[FJ80Steve]

Is the blend door just as much of a PITA as the core? Dash has to come out?

 

[Reko]

Would like to revive this tread..

I have the same issue... flushed, but water was as clean going in as coming out.. cable to control valve in firewall is not moving...
Any suggestions what it could be further on?

 

[Malleus]

The cable is controlled by the electronic climate control module in the dash. If you move the temperature lever, and the cable doesn't move on the engine side of the firewall, your climate control is at fault.

 

[Reko]

Where can I find this controler? I am already taking of my dashboard, I am afraid my front core is leaking also

 

[Malleus]

It is NLA for the North American models; I have no idea about the imports. You're not likely to find an import in a salvage yard here. Maybe one of the Aussies could find one for you there, and ship it here, if it's different than ours. You'd have to check the electronic parts catalogs and compare the parts lists.

@slow95z
@arcteryx

may have a North American model in their collection; you'd have to ask them, but again, I have no idea if they're the same, or at least interchangeable. I'd think they were, but I wouldn't care to speculate.

 

[Devils Paw 80]

Where can I find this controler? I am already taking of my dashboard, I am afraid my front core is leaking also

Do you mean where is it located in your 80? Easy, it's right behind the dash buttons.

 

[Reko]

I read a lot of (for me) different things. I can not understand that when the valve on the firewall is open, I do not have heat in the front of the car. So there must be another regulator.. my dash is almost taken out, I try to test the cobgroler asap.

 

[jht3]

I read a lot of (for me) different things. I can not understand that when the valve on the firewall is open, I do not have heat in the front of the car. So there must be another regulator.. my dash is almost taken out, I try to test the cobgroler asap.

so you disconnected the control cable from the valve, opened the valve all the way by hand, and you still don't have heat from the front?

 

[tmxmotorsports]

so you disconnected the control cable from the valve, opened the valve all the way by hand, and you still don't have heat from the front?

Do this you will bypass the electronic control

 

[Reko]

Done that, no solution...
Is this correct handling when I from cold to warm? It stops moving when I get in the middle part of the controler

 

[Reko]

Link to video

 

[Malleus]

If you have disconnected the valve on the engine side of the firewall, from the control cable, and have moved the valve from extreme position to another, and you still have no heat, your valve is not the problem. I would recommend looking at the diagram and then make certain the hoses are not blocked. If they are not, then the problem is in the heater core. It's directly behind the environmental control on the dash.

This is a view from the top; front of truck is at the top of the diagram:

The heater core is referred to as the "heater radiator", which it is.

 

[Malleus]

This is how the air gets into the cabin:

 

[Malleus]

EDIT: I added the link, so you don't have to walk through the menus to find it.

These are from the 1992 FJ80 Repair Manual (RM258U), which is located in the Resources section of the 80 series section.

 

[Reko]

Thank you very much! Great help!