have: 2000 S10 2.2L auto, ext cab, 190k miles
LED upgrade:
-LASFIT LED 14K & 6k LMs Super White
(2)9006 low beam (2)9005 high beam

issue:
-headlights worked for two months and 1000 miles after LED upgrade. then they would not turn on -both low and high beams. .

attempts:
-replaced dash light sensor and headlight switch...to no avail.
-replaced headlight relay (buried behind driver side dash in relay block) with new relay (tyco 3602 40A). this worked for two months and 1000 miles before headlights failed to turn on...again.
-checked headlight fuse as well and it is good.

note:
-auto dimming function works well (dash and radio both dim) when darkness is sensed.
-driving running lights work well.

questions: is the new relay replacement faulty? is the recommended 40A stock relay the problem? is it not powerful enough for the LED headlight upgrade? if the relay is the problem, is there a safe relay upgrade?

solution(s): ???

 

Did you open up the old relay to inspect it for damage? I'd look at the contacts in particular. Do you know the current draw of the mew LED lamps?

It could be that the relays are not able to take the current, especially right when closed.

 

good news, LED headlights are now working. after swapping the the two headlight relays (3602) 8 with 3 on the body relay block, i got the headlights to work again. for how long remains to be seen (see attachments).
note: i contacted the LED mfg (LASFIT) regarding the current draw -2.5 amps
note2: no, i never opened up the failed relays because they appear to be performing well; each failed relay was checked and the resistance on each .80 ohms + or - which is in passing range...i think. a contact test was performed using a 12VDC car battery and both passed with a clicking sound.
question: so why are the relays failing...or are they???

 

A failure mechanism for relays can be that the contacts on the armatures deteriorate from excessive current or arcing as they close and open. This can look like pitting and oxidation on the contacts.

 

I'll add 2 points to Christine's notes.

1. It's important to understand that relays and other electronics can measure differently under load vs disconnected on a bench. A contact that is corroded and pitted from arcing can measure fine with a multimeter on the bench because it's only trying to pass a tiny amount of energy for the meter. That same switch under load may have a massive amount of resistance because of the corroded contacts. Think of a pinched hose. If you're only supplying a tiny amount of water, it can pass easily, but when you turn on the tap you still only get a trickle. Similar concept.

2. Your problem may also be a grounding issue. This is less likely if changing the relay fixes the issue, but keep it in your back pocket as something to pursue if the problem persists with new relays. The headlight system uses a complex series of multiple switching grounds to control auto-high-low-DRL. If one of those grounds has failed, is loose, or is corroded then it could also be the source of your issues. You'll need a wiring diagram with grounding locations to chase this one, but it is possible. Grounding issues can cause really weird problems.

 

thanx, good to know. btw, LASFIT got back to me today with the current draw: 2.5 amp (per light?).