headlights flicker 1989 volvo 240 non turbo

122sPhil · Post by **122sPhil** » 01 Oct 2025, 12:14

Im seeng my headlights flicker, nothing is non original. no LED upgrades. euro style headlights.

ill check the spade ground conectors near the front of the fenders. maybe I have a bad brushes or bad regulator? its annoying enough that I had to take it off the road and its been sitting for 6 months or so waiting for love.

Anything else obvious that may cause this ?

Post by **volvolugnut** » 01 Oct 2025, 15:27

I would try to wiggle the headlight wires and connectors while engine and headlights on. Maybe in the dark with headlights shining on a wall so easy to see flicker while moving wires.
1989 should not have wire insulation rot problem, but heat may have failed insulation.
If single light problem, it could just be a bad bulb or contact.
volvolugnut

122sPhil · Post by **122sPhil** » 01 Oct 2025, 16:07

I thik it affects both headlights. it is quite an anoyoing flicker so I stopped using it it would bug other drivers for sure.

I do not know if I have a pulsating power issue of if this is a symptom of a bad ground. I do know where the headlights are grounded.

a bad ground puts an extra resistance in the circuit so that tends to dim the lights. the light and the bad ground are two voltage drops in series so they both use power thus reducing voltage available for the lights.

the cause of the flicker confused me. im thiniing but not sure tha tthe alternator is putitng out pulsating power.

maybe the brushes are so worn that they aren't always staying in comtact with the armature?

ive never had a diode in an alternator fail so I wans;t sure what that would cause. but I believe they do have a diode (or diodes) involved and they are within the case. a bridge rectifier is related. it could use one of those.

a diode allows current in one direction only. it can be used to turn AC into essentially rough pulsed DC. the nature of an alternator is that it makes AC at least initially, whereas a generator creates DC. maybe its a bad conection, Im not ruling anything out.

I thought maybe if I change the regulator in the alternar maybe I have worn brushes or womething causing a pulsation. bad diode maybe?

I guess I could connect an analog meter and see if the needle is swinging? harder to see pulsations wiht a digital meter. I guess an oscillosscope might show it better.