EATC heat issue

[turbo79]

I have a '92 SHO with an EATC system, and the heater function works poorly and inconsistently.

Most of the time it blows cool air despite the temperature setting. I just happened to be under the hood recently while at a gas stop, and I felt the heater hoses and the aluminum outlet from the engine and they were fairly cool. Yet, a couple of days later I did the same, found that the heater hoses were properly warm and, turning the temperature up, found that the system was putting out heat. The next day the "cool" condition returned. It stays cool most of the time, even after a 35 mile commute.

The engine comes up to proper operating temperature (according to the temp. gauge, which has a new sending unit) and does not leak any coolant.

I will add that the air conditioning does not work either, but that seems to be a separate issue.

I have run the self-test on the EATC head, and no trouble codes are being set.

Also, I recently changed out the radiator for a new one (the old one had a small leak from one of the core/tank seals - drivers side) so I don't think there is air in the system.

Thank you for any tips!

Tom F.
Deer Island, Oregon

By the way, my fiance and I just took this car on a near 3,000 mile road trip from Oregon to Colorado and back, first time on an extended trip in this rig, and it sure is a great open highway driver. Really good power considering the altitudes in CO.

 

[Racer X]

I would start by backflushing the heater core, provided the system has the appropriate level of coolant.

 

[turbo79]

I would start by backflushing the heater core, provided the system has the appropriate level of coolant.

By "backflush" do you mean force coolant through the core in the opposite direction it normally flows - which brings up the question of which direction it normally flows, if you know that?

The coolant level is at the so-called normal level.

Thanks!

 

[Devin]

The engine intakes coolant from the bottom of the radiator on the passenger side. It goes through the engine and ends up in the coolant manifold where it does several things, one of which is go through the big hose on the drivers side back into the radiator.

 

[turbo79]

The engine intakes coolant from the bottom of the radiator on the passenger side. It goes through the engine and ends up in the coolant manifold where it does several things, one of which is go through the big hose on the drivers side back into the radiator.

Thanks...

Your response suggests that the metal pipe that comes out from the engine from near the thermostat housing and goes to a heater hose is the inflow to the heater core. So I need to flush water into the other heater hose to reverse the direction and see if I can dislodge anything.

 

[Devin]

To tell you the truth I'm not sure which hose is the inlet and which is the outlet. I'd assume that the hose with the temperature sensor on it is the inlet, but I've never found a flow diagram.

Either way though, I don't think there are any one way valves in the heater core. As far as I know all it is is a small radiator. I'd just stick some silicon hose on one end of the heatercore so that you can divert the water from landing all over your engine and then somehow spray water into the other side.