np6

I have a strange problem in my 94 Grand Cherokee Limited. The other
day I turned the car off and the a/c blower motor (fan) kept running
even after I took the key out. I had to pull the fuse to shut it off.
The a/c and heater seem to work ok, it's just that the fan won't turn
off. I took it to a local mechanic who said I need a new HVAC control
head. The dealer has to order it, and it costs $700! Can it really
be that big of a problem to fix a blower motor that won't shut off?
I'm now popping the hood and putting the fuse in before I drive, then
pulling the fuse when I'm done. For $700, I'm thinking of building
some kind of switch that runs from the fuse to outside the hood so I
don't have to pop the hood. Any ideas?

Mike Romain

Ummm...

Maybe the sensor has failed?

Try a multimeter on it to see if it has a connection when cold, if so
replace it.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

np6 wrote:
>
> I have a strange problem in my 94 Grand Cherokee Limited. The other
> day I turned the car off and the a/c blower motor (fan) kept running
> even after I took the key out. I had to pull the fuse to shut it off.
> The a/c and heater seem to work ok, it's just that the fan won't turn
> off. I took it to a local mechanic who said I need a new HVAC control
> head. The dealer has to order it, and it costs $700! Can it really
> be that big of a problem to fix a blower motor that won't shut off?
> I'm now popping the hood and putting the fuse in before I drive, then
> pulling the fuse when I'm done. For $700, I'm thinking of building
> some kind of switch that runs from the fuse to outside the hood so I
> don't have to pop the hood. Any ideas?

Mike Romain

Ummm...

Maybe the sensor has failed?

Try a multimeter on it to see if it has a connection when cold, if so
replace it.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

np6 wrote:
>
> I have a strange problem in my 94 Grand Cherokee Limited. The other
> day I turned the car off and the a/c blower motor (fan) kept running
> even after I took the key out. I had to pull the fuse to shut it off.
> The a/c and heater seem to work ok, it's just that the fan won't turn
> off. I took it to a local mechanic who said I need a new HVAC control
> head. The dealer has to order it, and it costs $700! Can it really
> be that big of a problem to fix a blower motor that won't shut off?
> I'm now popping the hood and putting the fuse in before I drive, then
> pulling the fuse when I'm done. For $700, I'm thinking of building
> some kind of switch that runs from the fuse to outside the hood so I
> don't have to pop the hood. Any ideas?

DougW

np6 did pass the time by typing:
> I have a strange problem in my 94 Grand Cherokee Limited. The other
> day I turned the car off and the a/c blower motor (fan) kept running
> even after I took the key out. I had to pull the fuse to shut it off.


Tell the mechanic to get bent. :)

From your description and the base Limited, prolly the auto. So let's
start there.

I'm betting you have a stuck blower motor relay. That's the most
likely failure point.

Problem is I think the relay is in the control head. Should
be real close to the fan speed switch. Follow the trace back from
pin 4. Give it a good thwack with a mallet.. er.. tap it a couple of times
it might free up.

This schematic is very poor on that module, it almost looks like a
replacable 5 pin style relay, like a fog relay.

My scanner is down, but if you want the schematic just post a reply
with "DougW" in the subject line and I'll catch it easier.


--
-- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors

DougW

np6 did pass the time by typing:
> I have a strange problem in my 94 Grand Cherokee Limited. The other
> day I turned the car off and the a/c blower motor (fan) kept running
> even after I took the key out. I had to pull the fuse to shut it off.


Tell the mechanic to get bent. :)

From your description and the base Limited, prolly the auto. So let's
start there.

I'm betting you have a stuck blower motor relay. That's the most
likely failure point.

Problem is I think the relay is in the control head. Should
be real close to the fan speed switch. Follow the trace back from
pin 4. Give it a good thwack with a mallet.. er.. tap it a couple of times
it might free up.

This schematic is very poor on that module, it almost looks like a
replacable 5 pin style relay, like a fog relay.

My scanner is down, but if you want the schematic just post a reply
with "DougW" in the subject line and I'll catch it easier.


--
-- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors

Lon Stowell

Approximately 9/24/03 15:38, np6 uttered for posterity:

> I have a strange problem in my 94 Grand Cherokee Limited. The other
> day I turned the car off and the a/c blower motor (fan) kept running
> even after I took the key out. I had to pull the fuse to shut it off.
> The a/c and heater seem to work ok, it's just that the fan won't turn
> off. I took it to a local mechanic who said I need a new HVAC control
> head. The dealer has to order it, and it costs $700! Can it really
> be that big of a problem to fix a blower motor that won't shut off?
> I'm now popping the hood and putting the fuse in before I drive, then
> pulling the fuse when I'm done. For $700, I'm thinking of building
> some kind of switch that runs from the fuse to outside the hood so I
> don't have to pop the hood. Any ideas?

The blower motor is controlled by the ATC controls with
speed feedback. You may want to disconnect the battery
as it resets the control completely. This *could* be
as trivial as the high speed relay.

With the fuse in, turn it on, then turn the motor off.
Then pull the A/C fault codes.

Push AC and RECIRC at the same time. While doing this,
rotate the Temp **** one click Clockwise. This should
light all indicators as long if you keep your fingers
on the AC/RECIRC.


Take your fingers off the AC/RECIRC and the display should
go to 00, ready to pull codes. Push *either* the AC or
RECIRC but not both. The little stickman appears indicating
you are now in Diagnostic Mode. If the display stays at
00, the thing doesn't *think* the ATC module is bad. Push
the same button AC *or* RECIRC to step codes.

If you see fault 25 or 29, the ATC is bad and the rest of
any codes are bogus. Code 08 would indicate motor feedback
is too high, possibly not the ATC. 12 means the fan control
**** is bad. 16 means not enough motor feedback.

40 means at some point the feedback was too high but not
at the present. 48 is historical feedback too low. 61 means
the ATC was bad but thinks it is ok now.

To clear codes, push AC *or* RECIRC and hold for 3-4 seconds
until 2 bars appear on the display. Only clears codes
33 and higher.

You can pull detailed status by starting all over, push
AC and RECIRC, one click CW. This should turn on the stick
man and set to 00 or an uncleared fault code.

Step the tests by rotating the **** CW. OC is open ckt,
SC is short.

As you step the display with the ****, to read the inputs,
press either AC or RECIRC.

To actually test the outputs, go back to Diag Mode with
the AC/RECIRC trick and one CW click.

Then select the test you want to run by turning the Temp ****
CW and when it displays the number you want, push the AC
button to see the result.

Test No. What is checked Display
------- --------------- -------------------------

01 Blower Ctl Switch ?, OC, SC, 00-255

02 Blower Feedback ? 00-255

03 Blower Speed 00-255

04 Hi Speed Relay 00= off 01= on

If you push the RECIRC button during these, the value will
step and the motor should speed up/down.

And your warranty on this advice is roughly the same as
you paid for it.

Lon Stowell

Approximately 9/24/03 15:38, np6 uttered for posterity:

> I have a strange problem in my 94 Grand Cherokee Limited. The other
> day I turned the car off and the a/c blower motor (fan) kept running
> even after I took the key out. I had to pull the fuse to shut it off.
> The a/c and heater seem to work ok, it's just that the fan won't turn
> off. I took it to a local mechanic who said I need a new HVAC control
> head. The dealer has to order it, and it costs $700! Can it really
> be that big of a problem to fix a blower motor that won't shut off?
> I'm now popping the hood and putting the fuse in before I drive, then
> pulling the fuse when I'm done. For $700, I'm thinking of building
> some kind of switch that runs from the fuse to outside the hood so I
> don't have to pop the hood. Any ideas?

The blower motor is controlled by the ATC controls with
speed feedback. You may want to disconnect the battery
as it resets the control completely. This *could* be
as trivial as the high speed relay.

With the fuse in, turn it on, then turn the motor off.
Then pull the A/C fault codes.

Push AC and RECIRC at the same time. While doing this,
rotate the Temp **** one click Clockwise. This should
light all indicators as long if you keep your fingers
on the AC/RECIRC.


Take your fingers off the AC/RECIRC and the display should
go to 00, ready to pull codes. Push *either* the AC or
RECIRC but not both. The little stickman appears indicating
you are now in Diagnostic Mode. If the display stays at
00, the thing doesn't *think* the ATC module is bad. Push
the same button AC *or* RECIRC to step codes.

If you see fault 25 or 29, the ATC is bad and the rest of
any codes are bogus. Code 08 would indicate motor feedback
is too high, possibly not the ATC. 12 means the fan control
**** is bad. 16 means not enough motor feedback.

40 means at some point the feedback was too high but not
at the present. 48 is historical feedback too low. 61 means
the ATC was bad but thinks it is ok now.

To clear codes, push AC *or* RECIRC and hold for 3-4 seconds
until 2 bars appear on the display. Only clears codes
33 and higher.

You can pull detailed status by starting all over, push
AC and RECIRC, one click CW. This should turn on the stick
man and set to 00 or an uncleared fault code.

Step the tests by rotating the **** CW. OC is open ckt,
SC is short.

As you step the display with the ****, to read the inputs,
press either AC or RECIRC.

To actually test the outputs, go back to Diag Mode with
the AC/RECIRC trick and one CW click.

Then select the test you want to run by turning the Temp ****
CW and when it displays the number you want, push the AC
button to see the result.

Test No. What is checked Display
------- --------------- -------------------------

01 Blower Ctl Switch ?, OC, SC, 00-255

02 Blower Feedback ? 00-255

03 Blower Speed 00-255

04 Hi Speed Relay 00= off 01= on

If you push the RECIRC button during these, the value will
step and the motor should speed up/down.

And your warranty on this advice is roughly the same as
you paid for it.

Lon Stowell

Approximately 9/24/03 15:55, DougW uttered for posterity:

> np6 did pass the time by typing:
>> I have a strange problem in my 94 Grand Cherokee Limited. The other
>> day I turned the car off and the a/c blower motor (fan) kept running
>> even after I took the key out. I had to pull the fuse to shut it off.
>
>
> Tell the mechanic to get bent. :)
>
> From your description and the base Limited, prolly the auto. So let's
> start there.
>
> I'm betting you have a stuck blower motor relay. That's the most
> likely failure point.

Note that this relay ain't thar unless the unit has ATC. And
caution that this is from a 95 FSM, so YMMV. Fuse 11 goes to
the high speed relay. If the relay is on, it feeds a full
battery voltage to the motor. If the relay is off, the motor
speed is controlled by battery voltage being fed to the
motor thru the Blower Power Module, which could also be bad.
Variable speed is controlled by
the BlowerPowerModule which gets its feed from the ATC
controller.

The Blower Power Module is allegedly along the right side
of the Instrument Panel, fairly near the Auto Temp Controls
on that panel.

The High Speed relay is located along the right hand side of
the HVAC under the dash. It gets a one-line feed from the
Auto Temp Controller.

Unfortunately neither the FSM nor the Body Diag has any
better location info or pictures or even remove and repair
for those two items.



>
> Problem is I think the relay is in the control head. Should
> be real close to the fan speed switch. Follow the trace back from
> pin 4. Give it a good thwack with a mallet.. er.. tap it a couple of times
> it might free up.
>
> This schematic is very poor on that module, it almost looks like a
> replacable 5 pin style relay, like a fog relay.
>
> My scanner is down, but if you want the schematic just post a reply
> with "DougW" in the subject line and I'll catch it easier.
>
>

Lon Stowell

Approximately 9/24/03 15:55, DougW uttered for posterity:

> np6 did pass the time by typing:
>> I have a strange problem in my 94 Grand Cherokee Limited. The other
>> day I turned the car off and the a/c blower motor (fan) kept running
>> even after I took the key out. I had to pull the fuse to shut it off.
>
>
> Tell the mechanic to get bent. :)
>
> From your description and the base Limited, prolly the auto. So let's
> start there.
>
> I'm betting you have a stuck blower motor relay. That's the most
> likely failure point.

Note that this relay ain't thar unless the unit has ATC. And
caution that this is from a 95 FSM, so YMMV. Fuse 11 goes to
the high speed relay. If the relay is on, it feeds a full
battery voltage to the motor. If the relay is off, the motor
speed is controlled by battery voltage being fed to the
motor thru the Blower Power Module, which could also be bad.
Variable speed is controlled by
the BlowerPowerModule which gets its feed from the ATC
controller.

The Blower Power Module is allegedly along the right side
of the Instrument Panel, fairly near the Auto Temp Controls
on that panel.

The High Speed relay is located along the right hand side of
the HVAC under the dash. It gets a one-line feed from the
Auto Temp Controller.

Unfortunately neither the FSM nor the Body Diag has any
better location info or pictures or even remove and repair
for those two items.



>
> Problem is I think the relay is in the control head. Should
> be real close to the fan speed switch. Follow the trace back from
> pin 4. Give it a good thwack with a mallet.. er.. tap it a couple of times
> it might free up.
>
> This schematic is very poor on that module, it almost looks like a
> replacable 5 pin style relay, like a fog relay.
>
> My scanner is down, but if you want the schematic just post a reply
> with "DougW" in the subject line and I'll catch it easier.
>
>

L.W.(=?iso-8859-1?Q?=DFill?=) Hughes III

http://www.----------.com/blower.pdf
God Bless America, ßill O|||||||O
mailto:--------------------

np6 wrote:
>
> I have a strange problem in my 94 Grand Cherokee Limited. The other
> day I turned the car off and the a/c blower motor (fan) kept running
> even after I took the key out. I had to pull the fuse to shut it off.
> The a/c and heater seem to work ok, it's just that the fan won't turn
> off. I took it to a local mechanic who said I need a new HVAC control
> head. The dealer has to order it, and it costs $700! Can it really
> be that big of a problem to fix a blower motor that won't shut off?
> I'm now popping the hood and putting the fuse in before I drive, then
> pulling the fuse when I'm done. For $700, I'm thinking of building
> some kind of switch that runs from the fuse to outside the hood so I
> don't have to pop the hood. Any ideas?