Audio Preliminary Diagnosis. Cadillac Eldorado 1999

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 1999 🢒 Eldorado 🢒 Body and Accessories 🢒 Entertainment 🢒 Audio Preliminary Diagnosis

Many conditions that affect radio operation may be corrected without removing the radio from the car. Verify the condition, and follow the diagnostic procedures in order to isolate and correct the condition. Before attempting to diagnose any audio system problems, ensure that the battery is fully charged.

If the battery voltage is below 9 volts, incorrect diagnosis may result.

Troubleshooting Hints

Important: When testing for audio reception or noise, the vehicle should be outside away from metal buildings and utility lines, with the hood and rear compartment closed.

•	For reception concerns, first determine if the customer is within the listening area of the stations thay are attempting to receive.

•	Compare the customers vehicle to another of similar model and audio system to determine if the condition is abnormal.

•	Most normal audio noises can be found on weak stations near the low end of the band. This noise is considered to be a normal condition.

•	Check for any aftermarket equipment that may have been installed on the vehicle. If aftermarket equipment is found disconnect it and check if the audio noise is still present.

•	If the noise is only from one speaker check for the flowing before speaker replacement:

-	Isolate the noise using theJ 39916-A

-	Check that the speaker connections are clean and tight.

-	Check that the speaker mounting is tight.

-	Inspect for loose or incorrectly installed speaker or surrounding trim.

•	Ignition noise on the FM band may be a indicator of a ignition system breakdown.

•	Inspect that all vehicle grounds are clean, tight and free of corrosion.

Identifying Concerns

Important: When testing for audio reception or noise, the vehicle should be outside away from metal buildings and utility lines, with the hood and rear compartment closed.

To help isolate the source of the noise, identify the ignition switch position where the noise is most noticeable:

•	Turn the ignition switch to the ACCY position and listen for the noise.

•	Turn the ignition switch to the RUN position with the engine off.

•	Turn the ignition switch to the RUN position with the engine running.

Turn the ignition switch to the position that the noise was most noticeable.
Remove the vehicle fuses and circuit breakers one at a time until the noise has been eliminated.
Identify which systems or components are powered by the fuse.
Reinstall all fuses and circuit breakers.
Disconnect the components powered through the fuse one at a time until the noise has been eliminated.

Antenna Snifer Diagnosis

The antenna sniffer can be used along with the vehicles radio to locate hot spots that may be generating radio noise interference.

Antenna Sniffer


(1)	Inner White Insulator
(2)	Center Conductor Wire
(3)	6 cm (2 in)
(4)	Antenna Sniffer

The antenna sniffer can be made from a old antenna lead in cable by cutting off the antenna base lead in. Then strip off approximately 6 cm (2 in) (3) of the outer coax shield (black insulation and braided wire) leaving the inner white insulator (1) and the center conductor wire (2). Use the longest antenna lead as possible (4), for best results.

By plugging the antenna sniffer into the radio antenna socket you can use the stripped end to search for hot spots.

To use the antenna noise sniffer:

Important: When using the antenna sniffer keep your hand away from the stripped end while searching for noise.

Disconnect the antenna lead in and plug the antenna sniffer (3) into the radio antenna socket.
Turn up the radio volume.
Search for the noise source (1) along the wiring harness (2).

Important: Before measuring the resistance of the antenna, remove the negative lead of the battery and zero the J 39200 before taking measurements. When inspecting the resistance, cautiously wiggle the lead-in tip and cable. If the resistance does not match the ones listed, some portion of the lead-in is intermittent and needs to be replaced.

Coaxial Cable Testing Points


(1)	Antenna Mast
(2)	Antenna Base
(3)	Metal Case
(3)	Metal Case
(4)	Tip for Antenna
(4)	Tip for Antenna
(5)	Tip for Radio
(6)	Metal Case

Digital Multimeter Probes at Points:	Resistance Measured (Ohms)
ground and 6	less than 0.20
ground and 2	less than 0.20
ground and 5	infinite
ground and 4	infinite
Ground and 1	infinite
Ground and 3	less than 0.20
6 and 3	less than 0.20
6 and 2	less than 0.20
6 and 5	infinite
6 and 4	infinite
6 and 1	infinite

Corrective Action

•	Inspect the ground integrity of the component or system causing the noise.

•	Malfunctioning and marginal components such as relays and solenoids may cause noise and/or reduced reception.

•	Always use a braided ground strap when applying grounds and keep the ground strap as short as possible.

•	If the noise source is found to be coming from the vehicle harness:

-	Route the antenna cable separately from the wire harness that is emitting the noise.

-	Use aluminum or nickel tape in order to shield the antenna cable. Try varying the following techniques:

•	Try adding the tape before adding a ground strap to the tape.

•	Wrap a ground strap 360 degrees around the tape, securing the other end of the strap to a chassis ground.

•	Add a ground strap to both ends of the tape.

Important: When installing suppression devices signal wires, such as sensor and communication circuits, should not be suppressed. Battery and ignition voltage circuits are the best choices for suppressing.

•	Capacitors work best on switch pops and low frequency noise.

•	Filters work best on high frequency whines and static.

•	After adding any suppression device, inspect all of the vehicle systems (including those not related to the audio system) for proper operation and function.

•	Whenever possible, make a test harness that includes filters or capacitors. Always inspect the effectiveness and operation before permanent installation.

•	If an audible pop is induced from a switch operation, perform one or more of the following capacitor applications, as necessary:

-	Add a capacitor across the contacts of the switch.

-	Add a capacitor from the battery positive voltage (B+) side of the switch to chassis ground.

-	Add a capacitor from the ground side of the switch to chassis ground.

•	Use the following available noise suppression devices:

-	220 mF (50V) capacitor GM P/N 1227895

-	0.47 mF capacitor GM P/N 1227894

-	Fuse block capacitor

-	Feed through capacitor GM P/N 477371

-	Filter package GM P/N 1224205

-	Turn signal suppression

-	Fuel pump suppressor GM P/N 25027405

-	21 inch braided ground strap

-	19 inch braided ground strap GM P/N 6286800

-	10.5 inch braided ground strap GM P/N 6287160

-	8.5 inch braided ground strap GM P/N 12091511

Generator Whine Concerns

Test the ground terminal and cable for high resistance.
Inspect the generator and brackets for loose or coated mounting bolts.
Verify that the ground straps between the engine and the frame are clean and tight.
If the noise is still present, inspect the charging system for proper operation.
Install a filter, GM P/N 1224205, in the battery voltage feed circuit to the radio.
If the noise is not eliminated, install the filter in the following variations:

•	Install the filter with the single wire side toward the radio and the ground wire attached to a chassis ground.

•	Remove the ground to the filter.

•	Reverse the filter so the two-wire side is toward the radio with the ground wire attached to a chassis ground.

•	Remove the ground from the filter.

Install a filter, GM P/N 1224205, in the ignition voltage feed to the radio.
If the noise is not eliminated, install the filter in the following variations:

•	Install the filter with the single wire side toward the radio and the ground wire attached to a chassis ground.

•	Remove the ground to the filter.

•	Reverse the filter so the two-wire side is toward the radio with the ground wire attached to a chassis ground.

•	Remove the ground from the filter.

If the filter causes delays when turning the radio on or off (or any other problems), remove the filter and install a 0.47 mF capacitor to a chassis ground.
Before reassembling the vehicle, remove any unneeded filters.
Inspect all of the vehicle systems (including those not related to the audio system) for proper operation and function.