I'm hoping someone can help me out with this. My interior lights dim slightly when my turn signals are flashing (it's most noticeable in the gauge cluster and climate controls).

Here are things I have tried:

-My battery was working fine, but was about 7 years old, so I replaced it with a Red Top today.
-Big 3 grounding upgrade with 4-gauge wire.
-Alternator is < 3 years old (prostart, 90 or 100 amp)
-Problem happens when engine is off (key in ACC), car is idling, and in neutral when revving the engine

I have no other problems with the car. I have the corner lights wired via a relay to blink with the turn signals. I currently have 1157 bulbs in the corner lights. Could this be the cause? I haven't had a chance to pull the bulbs and try again. If this is what's causing it, is there anything I can do to prevent the temporary dimming and keep the corner lights as turn signals? It's not very noticeable, but it's annoying me.

Thanks in advance.

 

When lights dim, it means the voltage on a given circuit is dropping. This is usually caused buy an excessive current draw (too many things wired up together). Less voltage equals less light. Try disabling your relay if you think that might be the problem. But don't just pull the bulb, disconnect the coil.

 

Good call, thanks. I will disconnect the relays and try again. If it's the relays, can you think of anything that would solve the problem?

 

If you disconnect the relays and the lights don't dim, you need to satisfy the current requirements of the circuit. Somewhere along the line there is a bottle neck, and not enough electrons can get though at once. Think of it like a road that narrows at one point. If you increase the width of the road, more cars can pass. If you increase the diameter of the wire, more electrons can pass.

I don't have a schematic, but it seems like you are powering the relays with the turn signal circuit. Post again when you disconnect the relays completely, and test to see if the lights still dim.

 

Also, which lights dim specifically? All of them? Just the gauge cluster? Just the ash tray? And how low do they dim? Just a little? A lot?

 

I'll try to check without the relays tomorrow (the car is garaged a couple of blocks away). I understand what you're saying about needing larger wires; re-wiring the signal lights would suck. You are correct that the relay is being powered by the turn signal on each side.

I checked while I was in the car earlier, because I knew that before I replaced the battery, the clock was dimming slightly. With the new battery, the clock is no longer dimming. The dome light dims but it is so barely visible that I had to stare at it with my eye up against the ceiling for a couple of minutes before deciding that it was actually dimming. This is also less severe than it was with the old battery. The gauge cluster and console illumination are what dim the most and I don't think there's a difference from the old battery to the new. It seems mostly contained to the illumination circuit, but I'm not sure what that implies. The degree of dimming is hard to quantify; it's noticeable if you are looking at one of the lights that is dimming, but if you look elsewhere you can't see that anything is wrong (so it's nothing SEVERE, but I think it's worse than "normal").

Thanks for the help!

 

What relays are you using? I am most interested to see what current the coil is rated at. Try turning the illumination dimmer up, and see if the effect is less noticeable.

What filament of the 1157 are you using for the corner lights? There should be two, a 27 watt one and a 8 watt one.

When you test it later, pull the bulbs first, and check for the dimming, then disconnect the relay coil and check for the dimming. Also, you say that the relay is being powered by the turn signal circuit. I assume that means the coil, and I also assume the the power for the lights themselves, for the contacts of the relay, is coming from the corner light circuit. If your headlights and corner lights are off, do the corner lights flash with the turn signals, or do the corner lights only flash when the headlights are on?

 

Sorry for the delay... I've been sick and just got a chance to check this out yesterday. I took a picture of the relay, but of course left my camera in the car. The dimmer switch has no noticeable effect on the problem.

OK, so the dimming does occur when the bulb is pulled, and does NOT occur when the relay is pulled. I swapped out the relay I was using (looks like it came from Radio Shack) with the relay from the fog lights, and had the same problem.

Your assumptions are correct- the power for the lights via the relay comes from the corner light circuit, and the relay is being switched from the turn signal circuit. So the relay switches even when the headlights are off, but the corner lights only actually flash if the headlights are on.

 

I was wondering what happend to you, and if you got it fixed. Sorry to here you were sick, hope you are feeling better.

Where do you connect the ground for the relay coils?

 

Thanks. The power for the coil is spliced into the turn signal hot wire, and the ground is spliced into the turn signal black wire, so essentially the relay is wired in parallel with the turn signal.

EDIT: Sorry, I think this might be incorrect. I'll have to check tonight because my memory is fuzzy (I'll have to take pics this time).

 

Is there any way for you to measure the resistance of the relay coil?

 

I'll bust out my multimeter when I get home, provided it's not raining. Thanks for your help.

 

Awesome!

No problem, just want to get this figured out.

 

Me too!

It's raining pretty hard right now so I can't test the resistance of the coil, but I'm pretty sure it's a cheap Radio Shack relay, and according to their website that would make it 400ohms.

The way it is wired is:

Coil 1: Turn signal + (spliced)
Coil 2: Corner light GND (spliced)
Load 1: Corner light + (8w)
Load 2: Corner light HIGH (27w)

All splices are in parallel with the original wiring.

 

Let me know when you can double check the resistance of the coil. Something is not right about the tech specs on the Radio Shack website. If it's the relay I'm looking at (30A/12V) then it says the coil is rated at 12 volts, at 133mA having a resistance of 400 ohms.

12 volts != 400 ohms * 0.133 Amps

Ohm's law is a law for a reason, and I wouldn't trust Radio Shack for anything.

 

lol. Good catch. The weather is much nicer today so I'll take a look when I get home this evening.