Ozzstar

Ok guys, let's play name that annoying tune.....

My '93 has an annoying high pitch 'buzzing' sound coming from a electronic module of some kind below the passenger side dashboard glovebox, behind the carpet area. If the door is open without the engine running it makes a continues tone. It sounds like an angry mosquito! After the door is shut about 10-15 seconds later it stops and the courtesy lights behind the seats shut off automatically. Interesting thing is if I turn the brightness adjustment lever at the headlight switch all the way to the UP position (steady ON), the courtesy lights get brighter and the buzzing stops immediately. Put the dimmer switch back to the normal position and the buzzing comes back and the brightness of the bulb dims.

The key chime module above the climate control does not work most times. A spank on the dashboard has made it chime a couple of times. Are these related some how?

I also noticed with the key fob in the car, engine off, for example if i bump the car the annoying buzzing sound turns on for about 10-15 seconds.

What is going on under the dash? Thanks for in advance. - Ozz

Goldcylon

Pull the key chime above the radio

1993C4LT1

I had a similar sound you describe in my previous '93. Are all the interior light turning on when the door(s) are open? I only had the two back lights on, turned out to be a blown fuse. Replaced it and all was good.

Ozzstar

When the doors are open I only see the two interior back lights on behind the seats. What other lights should be on when things are working correctly? The car is new to me and I'm trying to find direction to correct the problem.

Thanks

Ozzstar

I assume you mean 'disconnect' the chime above the climate control. How will this eliminate the annoying buzz sound on the passenger side below the glove box?

I'd like to know what the module is and why it's buzzing.

1993C4LT1

Yes, your problem is most likely the dead fuse. The lights that should be on are-floor lights, map lights, and the door lights. I believe the fuse was 5 amp and was labeled "courtesy lights", but I'll go look at my car in a bit to make sure.

Ozzstar

Thanks C4LT1! None of the lights you mention are working on my car. I will check out the fuses, appreciate the input very much. If it is a blown fuse then i will need to find the short that caused the fuse to blow. FUN stuff.......

WVZR-1

Can you see the module that you're interested in knowing what it is? If you can read a part number off of it post that number and it's possible to likely help you.

Check of course your fuses etc first and I don't know why you would want to remove the module other than to just satisfy your curiosity as to "what it is". If you don't see a part number let's try number of wires and the colors. It might be possible to ID it that way also. Can you put your hand on it to "feel" the buzz.

I would remove "NOTHING"!

This is likely your concern. I believe your car should have a courtesy light relay under the dash on the right side and that could be your "BUZZING". That wouldn't have any exposed wiring. The relay would be in a group of relays under the dash RH side.

I don't have a '93 FSM but I believe it should be similar to a '94 and you would have 2 courtesy fuses labeled RH and LH.

"1993C4LT1" should be able to confirm that!

Ozzstar

Yes WVZR i can just barely touch it with my fingers and feel it buzzing, going out to check it now and see what I can find. Thanks

Ozzstar

Well you both win 1993C4 and WVZR!! It was a blown 5 amp fuse labeled RH CTSY, located on passenger side dash fuse box. Buzzing sound stopped and all the interior lights are functioning the way they should work!

That wasn't enough for me to just be. So here is some research I did.

I located the source of the buzz by removing the lower passenger panel. Under the glove box area there is a set of 4 relays all mounted next to each other, and another set of 2 relays side by side. The set of 2 is for the interior lighting. The relay closest to the drivers side which was buzzing is for the courtesy lights (floor,doors, map) and has the RH 5 AMP fuse AND the relay next to it is for the lights behind the seats. If you pull the 20 AMP LH CTSY fuse the lights behind the seat will go out. I'm not sure what else is tied to this circuit at t his time.

I removed the 'buzzing' relay and took it apart at the bench. The contacts looked good and no signs of corrosion or burning. It is connected to a 4 wire, BLACK, ORANGE, WHITE, and BLACK/GREY stripe. I'm pretty sure it was black w/ grey, but definetly a grey stripe. Hope this information is helpful to others.

I want to thank all who contributed with positive ideas and suggestions! Now the question is will I find the root cause of the blown fuse...... why did it short out? I have plenty to do on this car but when I have a chance I hope to find out. Take it easy- Ozz

1993C4LT1

Glad we could help ozz, that's what the forum is for
Good luck on the finding the cause

cmdrken1

This 6 year old post fixed a problem with my C4 too! I had jumpered the obd1 plug on my 93 coupe and the only code I got was H25. I've had the car for a month and I have been down the rabbit hole on this forum many times. I didn't know it had any interior lights besides the ones by the headrests. It's had the embarrassing buzzing since I bought it and while working on another issue (temp buttons intermittent) I pulled the 5a courtesy fuse and it was toasted. cannibalized my power mirror 5a fuse and let there be light! So now I have more interior lights and the buzzing is gone. To all of you guys that share the detailed fixes and C4 information THANK YOU!

Ozzstar

That's great news! It's been 6 years and the 5amp fuse I replaced still hasn't blown. I could never find or duplicate the short. Enjoy your C4, they are fun cars for the money! I have several C4 repair videos you might be interested in that are posted on my YouTube channel Ozzstar's Cars. https:www.youtube.com/ozzstar Take it easy! -Ozz

cmdrken1

Ozz thats +1 to your subscribers chief thanks again! -Ken