Heater - Low/No Heat When Set At Full Heat
Article No.94-20-16
10/05/94
HEATER - LOW/NO HEAT WHEN TEMPERATURE KNOB IS SET AT FULL HEAT
LIGHT TRUCK:
1992-94 BRONCO, F-150-350 SERIES
ISSUE:
Some vehicles may exhibit a low or no heat condition when the temperature knob is set to the full heat position. This may be caused by the temperature door cable not closing the temperature door fully.
ACTION:
Adjust the existing cable to obtain full door closure. If the cable cannot be adjusted sufficiently to obtain full door closure, replace the temperature control cable. Refer to the following for repair procedures.
DIAGNOSTIC PROCEDURE
1. With a low/no heat condition, diagnosis should always begin with a check of the vehicle's coolant to be sure it is at the proper level, concentration and operating temperature with the thermostat open. If it is below specification, it should be corrected first.
2. Bring the vehicle to normal operating temperature.
a. On 1994 F-Series/Bronco: If low/no heat condition still exists, replace the temperature door control cable. For proper procedures, refer to the Service Procedure which follows.
b. On 1992-93 F-Series/Bronco: If low/no heat condition still exists, perform the control cable adjustment procedure as outlined in the Service Procedure which follows.
c. On 1992-93 F-Series/Bronco: If low/no heat condition still exists, disconnect the cable at the plenum and "wire" the door shut in the full warm position. With the engine still running, set the blower speed on "High" and place the mode selector on "Floor". Check for proper temperature and discharge air volume at the floor duct. If the low/no heat condition still exists and the coolant temperature is still in specifications, the concern could be blockage in the duct work or plenum, air leakage which chills off the air after it goes through the heater core, or possibly a defective plenum. Further diagnosis is required.
d. If wiring the door shut in the full heat position resolves the issue, the problem is most likely in the cable and a new cable should be installed. For proper procedures, refer to Service Procedure which follows.
SERVICE PROCEDURE
ADJUSTMENT PROCEDURE
1. Open the glove box to gain access to the adjustment clip.
2. Pull back on the white tab on the adjustment as shown in Figure 4.
3. With the tab held back, move the barrel that travels through the clip in the direction required to obtain the proper door seating. Move the barrel one notch and verify that the door seats in each direction of travel.
NOTE:
DO NOT MOVE THE BARREL MORE THAN TWO (2) NOTCHES FROM THE CENTER POSITION IN EITHER DIRECTION. MOVING THE BARREL MORE THAN TWO (2) NOTCHES MAY RESULT IN BARREL DETACHMENT FROM THE CLIP DURING LATER OPERATION OF THE TEMPERATURE CONTROL.
4. On 1992 vehicles, follow Steps 1, 2 and 3. However, in Step 3, if more than two (2) notches of travel are required, check the cable and cam for binding. If there is no binding present, replace the temperature control cable (F4TZ-18518-A), the temperature control cam (F3TZ-19788-A) and the heater access cover (F3TZ-18B299-A).
5. After attaching the cable and clip, make adjustments to the clip and verify that the temperature door closes at both ends of travel.
6. On 1993 vehicles, follow Steps 1, 2 and 3. If in Step 3, more than two (2) notches of travel are required, check the temperature control cam for binding. Cam binding can be checked by detaching the cable from the cam and actuating the cam by hand. The cam should move freely. If it is binding, adjust it to eliminate the binding. Reattach the cable and verify that the temperature door closes at both ends of its travel. If the temperature door does not close properly, replace the temperature control cable using (F4TZ-18518-A), adjust if necessary and verify that the door closes properly. If the door still does not close properly, the problem is most likely in the control assembly.
a. Continue by removing the control assembly. Detach the cable from the control assembly.
b. Check the travel of the rack when the temperature knob is rotated to the full cold position. The notch in the rack should stop at the bullet connector bracket when rotated to cold. Refer to Figure 5. If it does not come within 1 mm or touch the bracket, replace the control assembly (F2TZ-19980-A).
c. Reattach the cable and verify that the door closes at both ends of its travel.
7. On 1994 vehicles, verify that the temperature door closes at both ends of its travel. If the door does not close properly, replace the temperature control cable (F4TZ-18518-A).
a. Adjust the cable if necessary and verify that the door operates properly.
CABLE REMOVAL
NOTE:
THE ADJUSTMENT CLIP IS ATTACHED TO A MOLDED-IN BRACKET LOCATED IN THE UPPER LEFT HAND AREA OF THE HEATER CORE ACCESS COVER. THE CLIP IS RETAINED BY TWO (2) TABS. THE HEATER-A/C TEMPERATURE CABLE CLIP REMOVER (D91T-18532-A, OR EQUIVALENT) IS REQUIRED TO DEPRESS THE LOCKING TABS IN ORDER TO ALLOW FOR REMOVAL FROM THE ATTACHING BRACKET.
1. Open the glove box door to gain access to the adjustment clip.
2. Position the removal tool over the bracket and clip as shown in Figure 3.
3. Align the opening in the removal tool with the retaining tabs which project through the bracket and pull back firmly (when properly aligned against the bracket, the tool handle will be horizontal but angled slightly downward). This will depress the locking tab but not disengage the clip from the bracket.
4. While maintaining the pull on the tool, pull the clip away from the bracket with the free hand.
5. Examine the adjustment clip for damage during removal. If one (1) or both tabs are broken or no longer spread away from the body of the clip, replace the clip (F1TZ-14A163-D).
6. Disengage the cable wire from the temperature door cam pin. Refer to Figure 1.
7. Refer to the appropriate Service Manual to remove the A/C Heater Control Assembly.
8. Disengage the cable connector and wire from the temperature door cam pin.
9. If the temperature door control cam is being replaced, it should be removed at this time. Refer to Figure 2.
10. If the heater core access cover is being replaced, it should be removed at this time. Refer to Figure 2.
CABLE INSTALLATION
1. Attach the new temperature door control cam (F3TZ-19788-A) if it is being replaced. DO NOT OVER TORQUE. Minimum torque is 0.7 N-m (6 in.lb.) and maximum torque is 1.7 N-m (15 in.lb.). Check for binding or too much movement effort and adjust if necessary.
2. Install the heater core access cover (F3TZ-18B299-A) if it is being replaced.
3. Install the A/C-Heater Control Assembly if it is being replaced. Refer to the appropriate Service Manual for installation procedures.
4. On the adjustment clip at the cable end, move the barrel so the red insert is on "center" and the red does not show out from either end. Further adjustment is not normally required, but can be made after installation, if necessary.
5. Attach the cable to the control assembly if not already attached in Step 3.
6. Attach the wire coil end to the temperature control cam. Be sure the cable is under the cable retainer. Refer to Figure 1.
7. Align the adjustment clip with the opening in the molded-in bracket as shown in Figure 3.
8. Push the clip firmly into place and ensure that both tabs hold the clip to the bracket (an audible click should be heard on engagement). Pull firmly on the clip to verify proper retention of the clip.
9. Rotate the temperature control to make sure the temperature door closes at both ends.
Parts Block
OTHER APPLICABLE ARTICLES: 91-19-10
WARRANTY STATUS:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage
OPERATION DESCRIPTION TIME
942016A Replace Temperature 0.6 Hr.
Control Cable - 1994
Models Only
942016B Adjust Temperature Control 0.3 Hr.
Cable Only - 1992-93
Models Only
942016C Adjust Temperature Control 1.0 Hr.
Cable And Replace Cam
And Cover - 1992 Models
Only
942016D Adjust Temperature Control 0.8 Hr.
Cable And Replace Control
Assembly - 1993 Models
Only
DEALER CODING
BASIC PART NO. CONDITION CODE
18518 08
OASIS CODES: 208000, 208100, 208999