Jeep A/C and Heater on Blink !! Related ??

I am posting this message for my son. He owns a 1998 Jeep Grand Cherokee
Ltd, with 5.2 liter V8 engine. Digital climate control (single, not dual)


About three weeks ago, his a/c went out. Just giving no cold air at all.
Blower would blow, but no cold air. This didn't happen gradually.... he
just noticed it all of a sudden.


Now, his heater has stopped working. Blower blows neutral, ambient air, but
no warm air. Engine temp and water temp seem normal, so he does not
suspect a bad thermostat. He wonders if he could have a bad heater core
?

Because both his a/c and now his heater are not working, we wonder if it
could be a problem common to both functions..... perhaps a glitch in the
Digital climate control (again, single, not dual) ??

Any thoughts or suggestions ? Are they likely related ?

Thank you for any advice !!!

James

James wrote:
> I am posting this message for my son. He owns a 1998 Jeep Grand
> Cherokee Ltd, with 5.2 liter V8 engine. Digital climate control
> (single, not dual)
>
>
> About three weeks ago, his a/c went out. Just giving no cold air
> at all. Blower would blow, but no cold air. This didn't happen
> gradually.... he just noticed it all of a sudden.
>
>
> Now, his heater has stopped working. Blower blows neutral, ambient
> air, but no warm air. Engine temp and water temp seem normal, so he
> does not suspect a bad thermostat. He wonders if he could have a
> bad heater core ?
>
> Because both his a/c and now his heater are not working, we wonder if
> it could be a problem common to both functions..... perhaps a glitch
> in the Digital climate control (again, single, not dual) ??
>
> Any thoughts or suggestions ? Are they likely related ?
>
> Thank you for any advice !!!
>
> James

AC cutting off can be as simple as low 134a level. Just don't add
some before checking as that can cause kill the compressor.

However this sounds a bit like the blend door or blend door motor
has failed.

Have him run the diagnostics on the AC system.
Think this works. I'm using a 93ZJ manual.

Depress AC and RECIRC at the same time and hold
Rotate the knob clockwise (right) one click.

All the lights will light up (segment test)

Release the buttons and display will show 00

Press AC and release

You will see a series of number. write these
down. The numbers will repeat.

I suspect it is the blend motor.

If you do a google search for "ZJ blend door" there
are a lot of articles out there. Including some youtube
test videos.

--
DougW

very nice info Doug, I am passing this along to him now....

Thank you very much !!


James

Doug, my son did the test as you instructed, and he gets the following code:


38 / 46 / 55 / 56

What does this tell you (us ) ??

James

James wrote:
> Doug, my son did the test as you instructed, and he gets the
> following code:
>
>
> 38 / 46 / 55 / 56
>
> What does this tell you (us ) ??

38 - Blend Air Door Feedback (circuit open)
46 - Blend Air Door Feedback (circuit short)
55 - Blend Air Door Actuator (travel range too short)
56 - Blend Air Door Actuator (travel range too long)

Odd mix, but definitly the blend door motor system.
The bad news is this is a pain in the ass to fix.
So either it's going to be some time working on the
problem or $$ at the dealership.

With any luck it's just a connector. From what I
remember you get at it through the glove box.
Follow the youtube video below, it should help.

I don't have any good diagrams of that part. But
I do know replacement usually requires removing
the entire dash. (a very un-fun thing to do)

While I've never used these folks, they do have some
instructions. http://www.heatertreater.net

Check youtube also. There is a multi part walkthru.
http://www.youtube.com/watch?v=ZCMUrYUDYGw


--
DougW

Thanks again Doug, I am passing this along to my son !!

James