I have a '94 convertible (LT1)that been giving me little to no heat.
Both hoses going into the firewall were hot and I am getting SOME heat.
Today, I think I stumbled upon a possible cause and I'm hoping that
someone who's been there/done that has the cure.
I had to change out the Surge tank/overflow hose & pipes today due to a
leak. In the process of bleeding out the system and taking it out for a
shake down run I noticed something peculiar. Even though I'd cranked
the heat all the way up to 90 degrees after the engine warmed up, as
usual I received very little heat at the floor level. The REALLY
strange thing was the A/C never cut out. The pipes were collecting
moisture (even though it was set to put out maximum heat and ambient
temperature was < 82 degrees)and the system pipes that are normally
supposed to be cold when the A/C is running were as cold as the
proverbial witch's left **
*. It seems the A/C never shuts down.
To further test my theory I turned the automatic climate system OFF and
drove about 30 miles in 62 degree weather with the interior temp set to
90 degrees. While I could feel very little warm air coming in (since
the system was off) I DID feel some heat. I pulled into a lot and
lifted the hood to check the A/C components. All were at ambient under
hood temperature as you'd expect.
Shut the hood and took off, turning the climate control back ON for the
remaining 10 mile run to the house. As soon as I turned the system ON
the heat literally gushed out at the floor level and it was really
putting it out. As I continued to drive, however, the output cooled
down and the "heated air" was, at best, merely tepid. When I arrived
back home I again popped the hood and found the aforementioned cold
parts very frosty again. The damn A/C is tempering the hot air output.
No, the defroster was not on - I realize that that will cycle the A/C.
I tried it with the lower vents selected as well as the Automatic mode
and it really didn't seem to make much difference. The output
definitely cooled down once the A/C got going. Seems like I'm taking
all that nice hot air and forcing it through the A/C unit or vice versa.
Question is: How is the A/C controlled in this system. Is there a
relay that is supposed to take it off line? Is it the control head
that's FUBAR? I had been thinking I had a door stuck in the heater or
something. Apparently that's not the case since I have a good air flow
coming through down there.
A/C works fine, it just seems that it's working way too much and should
be taking a seat on the bench when I'm calling for a cabin temperature
above the ambient temperature.
Any help or advice would be very much appreciated.