Try this out - pull out the bulbs from the receptacles, hold the metal part of the bulb with one hand and the glass part with your other hand (use a tissue with the glass part for safety) Wiggle it a little and check if the glass part has become loose already. Often times on relatively old cars (5 years and above) like mine - the bulbs have fossilized inside and ruin the connections internally. You will not be able to see this outside. This will be the best test - wiggling Hope this helps.