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TSB 08-32-96

Blower Motor Relay Diagnosis

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Date: Oct. 4,1996

Models: 1994 -1996 (BR) Ram Truck

NOTE: THIS BULLETIN APPLIES TO 1996 RAM TRUCKS BUILT AFTER MARCH 15, 1996 (MDH 031 SXX) AND 1994 - 1996 RAM TRUCKS BUILT THROUGH MARCH 15, 1996 UTILIZING IGNITION SWITCH SERVICE KIT PIN 4874996.

Discussion:

Vehicles built after March 15,1996 and vehicles that have ignition switch service kit PIN 4874996 installed have the addition of a blower motor relay to the electrical system. This bulletin provides information and diagnostic test procedures for the blower motor relay circuit.

 

NOTE: RAM TRUCKS THAT HAVE THE IGNITION SERVICE KIT INSTALLED CAN BE IDENTIFIED BY VERIFYING THAT THE BLOWER FAN RELAY IS ATTACHED TO THE STOP LAMP SWITCH BRACKET (FIGURE 1) AND THAT THE COLOR CODE OF THE WIRING MATCHES THAT OF THE WIRING DIAGRAM (FIGURE 2).

CAUTION: SOME RAM TRUCKS ARE EQUIPPED WITH FOG LAMPS AND THE FOG LAMP RELAY, WHICH IS ALSO ATTACHED TO THE STOP LAMP SWITCH BRACKET, MAY BE CONFUSED WITH THE BLOWER FAN RELAY.

The blower motor relay provides battery voltage to the blower motor when the ignition switch is turned to the RUN position. The relay is located in the passenger compartment and is attached to the stop lamp switch bracket (Figure 1).

 

The 1996 Ram Truck Service Manual (Publication No. 81-370-6108), page 8W-42-4, provides the wiring diagram that supports vehicles built before March 15, 1996. The following wiring diagram (Figure 2) takes place of the fuse circuit (Fuse F2) and the blower motor wiring diagram for vehicles built after March 15, 1996. This diagram can also supplement 1994 Ram Truck Service Manual (Publication No. 81-370-4108), pages SW- 146 and 8W-147 and the 1995 Ram Truck Service Manual (Publication No. 81-370-5108), page SW-42-4, for vehicles that have ignition switch service kit P/N 4874996.

The blower motor relay is installed in series between the ignition switch and the blower motor. When the ignition switch is in the RUN position, battery voltage is provided to the relay terminal 86 (relay coil) from ignition switch terminal 5 (A22 12BK/OR circuit). Terminal 85 of the relay (relay coil) is routed to a ground. Refer to the appropriate Service Manual for ground splices and locations (G202 for 1996, G203 for 1995, and Z3-1 splice for 1994).

Battery voltage is supplied to terminal 30 of the relay (moving contacts of relay - Cl 12DG) from the Power Distribution Center Fuse 2 (A2 12PK/BK) through Fuse F2 in the Fuse Block. Terminal 87 of the relay (stationary contact) is connected to the blower motor (Cl1 12DG).

With the ignition switch in the RUN position, the blower motor relay coil is energized. With the relay energized, the movable contact of the relay is connected to the stationary contact providing battery voltage to the blower motor.

Symptoms:

Inoperative blower motor can be caused by any of the following components or circuits:

Diagnosis: 

This bulletin will provide diagnosis for the blower motor relay circuit only. For information regarding diagnosis of other blower motor circuit components, refer to the appropriate Ram Truck Service Manual.

BLOWER MOTOR RELAY CIRCUIT TEST

For the following tests, refer to Figure 3.

NOTE: ALL VOLTAGE CHECKS SHOULD BE MADE BY BACK-PROBING THE RELAY WIRING HARNESS CONNECTOR WITH THE RELAY CONNECTED TO THE CONNECTOR.

 
TERMINAL LEGEND
NUMBER

IDENTIFICATION

30
Common Feed
85
Coil Ground
86
Coil Battery
87
Normally Open
87A
Normally Closed
Figure 3 - Blower Motor Relay

 

STEP
ACTION
YES
NO
1

Turn the ignition key to the RUN position.

Turn the blower fan ON.

Is the blower fan motor running?

System is operating property at this time. Go to step 2.
2

Is the blower fan motor running? Check for battery voltage at terminal 87 of the blower motor relay (ignition ON and relay energized).

Is there battery voltage at terminal 87 of the blower motor relay?

Refer to the appropriate Service Manual for diagnosis related to inoperative blower motors, blower motor resistor, blower motor switch, heater-A/C mode control switch Go to step 3.
3

Check for battery voltage at terminal 30 of the blower motor relay.

Is there battery voltage at terminal 30 of the blower motor relay?

Go to step 5. Go to step 4.
4

Inspect Fuse F2 of the Fuse Block for damage or open circuit.

Is Fuse F2 damaged or have an open circuit?

Check and repair any shorts to ground In the blower motor circuit, then replace the fuse. Repair any open circuit in the C1 12DG wire and/or the A2 12PK/BK.
5

Check for Ignition voltage at terminal 86 of the blower motor relay

Is there ignition voltage at terminal 86 of the blower motor relay?

Go to step 6. Repair the open in the A22 12BK/OR circuit.
6

Check for ignition voltage at terminal 85 of the blower motor relay.

Is there ignition voltage at terminal 85 of the blower motor relay?

Repair the Z3 circuit for an open to ground. Replace the blower motor relay.

Notes: 

Policy:    Information only.


Thanks to Bob Bergevin and Barry Drodge for supplying this TSB information

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This page was edited on: May 3, 2004