Baja Designs SAE foglight flicker on idle
 

Getting some flicker from BD SAE foglights when idling

Tried two wiring schemes: 1) through the BD harness 2) stock oem foglight wiring. Same result.

Flicker appears if I come to a stoplight, strange thing is it persists after I start moving again and engine rpms are up. I have to cycle OFF/ON to restore non-flickering operation, then it's fine until I reach another stoplight (or possibly even when coasting). It also doesn't flicker right away if I cold start.

Alternator is a relatively new rebuilt cold-weather OEM, getting high 13s on the voltmeter at idle. I don't think it's a low voltage issue as the flicker doesn't happen when running off the battery, engine off, when voltage is lower. Battery is only a year or two old.

Flicker frequency isn't consistent, but seems to be almost be a repeating pattern if that makes sense. It's like the alternator is noisy, wish I had a portable scope to see if there are momentary voltage fluctuations.

Thought I already posted this but can't seem to find it, so reposting now...

Some of the auto parts stores have portable battery testers that they can take out to the vehicle. Some of these testers have a 'test the vehicle' option which should tell you if you have noisy power (ripple) from your alternator. I'd call around. The fairly basic one we have at work will do this.

Assuming I do have a power ripple, whats the solution?

I thought about trying to wire an electrolytic capacitor across the fog light relay , but I don't like experimenting too much with the vehicle's electrical system. Also not sure what value I'd try, and what potential issues it could bring. Maybe a fuse inline with the cap just in case it goes bad

A well charged battery in an otherwise OK charging system should take up the slack at stop lights (idling in gear) from any electrical accessory.

Should not need any extra electrical gimmicks to make it work correctly. Meaning something is wrong, whether is be weak battery, connections, alternator, as others said have each item checked to cross them off the list. Luck.

It's strange, i'd expect to see some flicker from other my interior LED lights or some other signs that the alternator / battery is bad. I have a voltmeter wired up inside the cab, and it doesn't sag much when I run tons of accessories. No issues starting either.

I do have a pesky P0171 engine code, mechanic has tried to remedy a few times replacing vacuum lines with no luck. Not sure if that would have any effect...