thank u for ur reply.could it be only the bulbs??????

Yes.
Start simple = replace the bulbs first..

Note:
If an aftermarket radio has been installed, verify the power and/or ground is NOT connected to the lighting or climate control circuit.






Have a great day.

__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

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Gentel men thank u for ur help.i changed the bulbs but no change sfter 20min with the heater on the bulbs dimmed and then went out.after i restarted the cac they went fine for 20min.
As for the radio it was installe ten years ago and never had any problem.
So whats next i wonder???????