I have a 1997 p38 4.0 and have replaced the climate control unit with one that I bought from ebay.

The unit hooks up fine, and when the truck is powered on there is illumination to the screen, that is, the screen is blank green.

NO buttons illuminate when pushed however, and no air blows from the vents.

The Rave manual states that the "ATC ECU (Hevac / Headunit) must be initialized using testbook to ensure correct operation of the AC system"

I have read on this forum and elsewhere where it's just a plug and play operation and testbook is not needed. So which is it and how do I get any air to blow in the truck.

I have checked all fuses, all check out fine. I have pulled relays and inspected, all seem fine as well.

I could really use any input that ya'll might have as you have been incredibly helpful in the past.

Thanks

 

plug and play. if you have no screen or function lamps send it back you got a bad head unit.
That being said there could be many reasons that the blowers don't work...

 

I appreciate the reply, the only thing is this is the 2nd head unit that has acted this way and they came from 2 different sources. I think there is something going on where the BeCM is not recognizing the headunit, or needs a restart in order to recognize it.

I have taken the negative battery cable off the battery for several hours without luck. Any other ideas on how to reset the BeCM?

Any tests I could run to make sure that BeCM is working properly?

 

no amount of hard resets are going to help you
What is the part # of the head unit you have it should be jfc102550.
there are so many things to cover here.. try turning your ignition key back
from crank position. they used to get stuck in crank pos and the display would go blank.
Next you'll need to check power to the head unit. heres a description copied from the etm. basically becm fuse f8 and f17.. F17 is the main power it is a white wire. Try and find a copy of rave to check for power at the head unit from the 2 becm fuses.

CIRCUIT OPERATION
Ignition position 1 (Accessories)
This feed is obtained from the BeCM via fuse 8 and
is shared with the Radio, Front cigar lighter, Aerial
amplifier and car phone (if fitted). The Ignition 1 is
essential to the control panel as it provides power to
the ECU although no functions or display on the LCD
are possible.
Ignition position 2
This feed is obtained from the BeCM via fuse 17.
Battery feed
This feed is obtained from the fuse box via fuse 42.
Ground Connection
This feed runs down to a spliced joint, joining the
main earth run down to fascia earth point 1.
Dimmer Line
This Pulse Width Modulated signal is provided by the
BeCM.
LCD Dimmer line
This line is a input to the HEVAC and the signal is a
inverse Pulse Width Modulated signal which is
determined by the instrument pack.
Compressor Clutch
The clutch line provides a 12 volt power feed to the
compressor clutch via pressure switch 1.
Condenser Fans
The HEVAC panel provides a signal normally at 12
volts for “off” condition and 0 volts for the “on”
condition, which in the case of petrol vehicles is fed
into the ECM and diesel vehicles directly onto the
coil of relay 18. In line is the Air–Conditioning
pressure switch 2, which turns the fans on/off.
When relay 18 is energised, it provides connection
between relays 13 and 14 (fan 1 and 2) in series or
parallel with each other. This is dependent upon the
state of the air–conditioning pressure switch 1.
For the petrol option, when the signal enters the
ECM, the ECM will switch the output on/off to the
fusebox. The ECM will switch the output on
sometimes for engine cooling reasons even though
the engine has been turned off.
Aspirator
There are two parts of this sensor, one of which is a
fan which draws cabin air onto the temperature
sensor. The temperature sensor then sends the
signal back to the HEVAC ECU.
Ambient Sensor
This sensor measures the temperature of the
external air flow into the vehicle.
For vehicles with VIN’s up to 381430:
The ambient temperature sensor is located behind the
drivers side of the fascia.
For vehicles with VIN’s from 381431:
The ambient temperature sensor is located behind the
LH side of the vehicle in front of the condenser. The
revised location improves the response time of the
sensor. The new HEVAC software will not update the
ambient temperature sensor readings unless the
vehicle is travelling over approximately 15 mph (25
km/h). The HEVAC software will therefore not automatically correct temperature readings when a faulty
ambient temperature sensor is renewed.
Temperature Resistance (Ohms)
–20° C (–4° F) 94.5 K
–10° C (14° F) 54.3 K
0° C (32° F) 32.1 K
10° C (50° F) 19.7 K
20° C (68° F) 12.5 K
30° C (86° F) 8.1 K
40° C (104° F) 5.4 K
Heater Core Sensor
This sensor measures the engine coolant
temperature within the fascia area.
Evaporator Sensor
This sensor is located within the evaporator unit and,
by providing feedback to the HEVAC ECU, prevents
it from freezing.
Alternator Charge signal
This signal is given to the HEVAC ECU to inform it
that the engine is running. This signal is active low.
Diagnostic K line
This line is used to communicate with the diagnostic
equipment (TESTBOOK) and is normally held at 12V
when not active.
Road Speed
This signal is fed into the HEVAC ECU.
Solar Sensor
This sensor provides the HEVAC ECU with the
power of the sun’s solar load and allows the system
to compensate accordingly.

 

headunit part number is correct...

I will preform the other tests tomorrow when I have additional time.

Thanks

 

I preformed a test at the plugs of each of the ATC ECU connectors (C244, C245, C246B, C261)

Here is what I observed

C244
PIN Volts
1 12.08
2 12.1
3 .3 (200mV)
4
5 24.3 (200 mV)
6
7
8

C245
PIN Volts
1
2 1.6 (200 mV)
3
4
5
6 1.5 (200 mV)
7
8
9
10
11
12


C246B
PIN Volts
1
2 2.3 (200 mV)
3
4 2.0 (200mV)
5 2.2 (200mV)
6 1.9 (200 mV)
7 2.0 (200mV)
8 2.2 (200mV)
9 2.3 (200 mV)
10 2.2 (200mV)
11 2.2 (200mV)
12 1.8 (200 mV)
13
14 1.8 (200 mV)
15 2.2 (200mV)
16
17
18 2.4 (200mV)
19
20


C261
PIN Volts
1 2.1 (200mV)
2 1.7 (200 mV)
3
4
5
6 2.2 (200mV)
7 2.6 (200mV)
8 2.2 (200mV)
9 2.3 (200 mV)
10 2.4 (200mV)
11 2.2 (200mV)
12 2.4 (200mV)
13 2.2 (200mV)
14
15 2.3 (200 mV)
16 2.3 (200 mV)

The only number that seemed odd was pin #3 (ignition power supply) on C244 reading .3 (200 mV) when the other power supplies read 12.08 and 12.10 V. Any ideas if this is the right voltage, or if corrective action is needed.

Your assistance is appreciated.

 

This problem persists. Any help from the forum would be appreciated. Thanks