No heat from heater
 

1987 turbo II gets no heat. A/C and all directional (head, feet, defrost) buttons work. Car runs fine and never overheats. Any ideas?

watch and listen to the blend door actuator while working the temp slider between hot and cold. the blend door actuator is right above the heater core water lines inside the cabin on the left side of the car driver side.

the actuators tend to jam up, sometimes bumping them will cause them to work again.

I second the water valve actuator, but its also worth pointing out that the logicon temp slider itself can go bad. Additionally, the heater core is at an age where it probably needs replacement anyway. Over the years, buildup inside the heater core causes the heat to stay trapped inside the core rather than radiate it.. this happened to me. I had zero heat whatsoever due to an old heater core. Replaced it, and had heat immediately.

You can replace the core without removing the dash, so no worries there.

Are both heater core hoses hot?

How much work did removing the heater core involve? How long did it take you?

You have to remove the whole dash, which might take 1-2 hours depending on your aptitude and tools.
I had the same issue last winter and found that the heater control valve on the heater core was jammed shut.

You could try to reverse flush the heater core. This link to ChrisFix would better explain it.


Cheers,
George

This is totally incorrect.
There is absolutely no reason to remove the dash.

Remove the steering column trim, the nut heater vent and duct, and you can remove the two screws that hold the cover over the heater core. Remove the small soft hoses to the core itself and the core can slide out of the heater box, but you will have to unbolt the column (4 fasteners) and lower it to have space.

I went all out and removed my seat and my carpet because I didnt have very many towels to be able to absorb the coolant that will come out when you remove the core (even tho you drained the coolant).

Removing the dash, while easy if you've done it before, is time consuming and you will just end up breaking things.

Thanks! That's very helpful information.

No problem.

Wow, I feel dumb. You absolutely will break shit if you pull the dash too. I should have googled that one.

Both hoses are hot once the car warms up. I will check the accuator but how can I test to see if the problem is the logicon temp slider and what is involved in repairing or replacing it

Oops, just reread the question about whether the both hoses are hot. Thought it meant hoses from the radiator. I don' know if both hoses are hot from the heater core Will try to check.

Rick,

The inlet hose to the heater core is on the driver side firewall and the outlet hose from the heater core is on the passenger side firewall. The closest reference to them are in Section E of the FSM, Pg E-2 Diagram. This diagram only shows the connection to the engine and radiator. Additionally, some functions of the Logicon can be tested. Refer to the "Checking logicon switch assembly circuit" in Section U of the FSM, beginning on Pg U-26. This testing requires the removal of the logicon so follow Pg U-22 for removal instructions. I also have a How-To on removing/installing the instrument panel garnish here: https://www.rx7club.com/2nd-generati...stall-1105124/

Cheers,
George

You can verify the temp valve is working with the ignition on and looking up under the drivers side of the dash at it, just move the temp slider on the logicon. Given the age of the car and the high probability the cooling system has not been flushed anything like as often as it should have been over these long years, I can just about guarantee the core simply needs to be replaced.

Rick,

Have you made any progress with the heater core? Don't forget about the Logicon as a possible failure. Smikels (Shane) from this thread https://www.rx7club.com/2nd-generati...0-min-1121088/ discovered his no-heat condition resulted from a faulty Logicon. It has a bad solder joint on the Temperature slider. Refer to the photos in his thread.

Cheers,
George

I had the same issue and it ended up being the actual control valve was jammed close. Replaced the heatercore/valve and good to go. BTW, you WON'T be able to actuate the valve manually if the linkage is still attached. You must disconnect the little metal rod if you want to check if the valve is stuck.

Thanks for the reply.
i had the dash/vent panel off when i changed the logicon. I could see the linkage for the heat actuator valve and it wasn’t moving when I moved the heat slider on the logicon, so I took a coat hanger and bent it so I could pull on the linkage, and it started working. I’ve tried it several times and I now have heat!
thanks to everyone involved in this thread!

watch and listen to the blend door actuator