Radio - Interference When Tuned to Weak Stations

CATEGORY
Electrical

SECTION
3

PAGE
41

ISSUE
04/93-0328

CODE
346

Subject:
Open Circuit in Electrically-Heated
Rear Window and Radio Interference

Application:
All 900 and 9000 Models

A complaint of poor reception when the radio is tuned to weak stations may be due to microscopic cracks in the electrically-heated rear window's heating wires. Such microscopic cracks may cause electrical interference when the electrically-heated rear window is switched on, and this may affect radio reception. While listening to a weak radio station turn the rear window defogger "on" and "off" several times and see if you can detect a difference in the background noise. If you can, proceed as outlined below.

Cars Affected:

All 900 and 9000 Models

Parts:

Electrically-conducting paint (may be obtained from a local vendor, such as, Radio Shack) Voltmeter Flexible plastic ruler or equivalent substitute Razor blade

Action:





1. Connect one of the voltmeter leads to the ground (negative terminal) of the electrically-heated rear window, Figure 1.

2. Switch on the ignition and activate the electrically-heated rear window.

3. Start by taking a reading in the center of each heating wire.

The voltage indicated should be half the battery voltage. If the reading obtained differs by more than 3 volts from half the battery voltage, there is a crack or other damage in the heating wire tested.





4. Take readings all along the suspect wire. The damage or break in the wire is at the point where the greatest voltage difference occurs, Figure 2.

Mark the place on the wire where the damage or break has been found. Test the other wires as described above.

WARNING

Switch off the ignition and the electrically-heated rear window.

5. Clean the area around the damage or break. Carefully remove a few millimeters of the protective enamel around the damage or break in the heating wire with a small wire brush, similar to that in the cap of Saab touch-up paint sticks. This will ensure good adhesion of the electrically-conducting enamel.

6. Apply the electrically-conducting enamel overthe damage or break in the heating wire. Allow it to dry thoroughly.

WARNING

Exercise care when using the razor blade, it is easy to cut yourself or damage the heating wire.





7. Carefully cut away surplus electrically-conducting enamel with the razor blade. Use a flexible ruler or the like to help you make a straight cut and avoid damaging the heating wire, Figure 3.

8. Check the operation of the heating wire (as described in step 3) after completing the repair.

Warranty Information:

For warranty repairs, use failure coding 84353-63-2-01-05. Time allowance for diagnosis and repair is 0.5 hours which should be entered as straight time. Reimbursement for the actual amount of electrically-conducting paint used may be claimed as a sublet amount.