MustangBatman1

I wired a button for my purge kit and every time I press the button to purge, the speakers make a popping sound when I let go of the button. The button is getting it's power from the cig lighter wire if that makes a difference.

Any idea whats causing this?

157dB

Does your S197 have a cig lighter?
Maybe you mean the power point in
the center of the dash area?
Its the PIV generated by the coil
when power is removed thats causing
the popping noises.
A diode across the purge solenoid
coil would fix this popping noise condition.

Z06 Killer

^ I agree. Either that or you may have tagged into the amp power or turn on line

MustangBatman1

That's what I meant by cig lighter, I forgot what it was called, and I was too lazy to try and remember since I literally woke up and posted.

Thanks for the info.

dkersten

157db is correct. Any time you put power to a coil of wire you will get a charge built up, which will release when you remove power. In this case, the solenoid for your purge is the coil, and since you are powering it with a common 12v wire that is not isolated, it sends a jolt back through the rest of the wiring.

As I picture it in my head, you have a momentary switch with 12v from your lighter on one side, and the solenoid for the purge on the other. The solenoid is grounded on one side and the switch is on the other. The problem is when you release the switch, the charge is going to ground, so a diode would probably not cure that. (then again, dropping a charge to ground shouldnt cause a problem with the stereo since the charge will be high in voltage but low in current and the ground is the whole chassis of the car) If the switch was the ground and you had power to the other side of the solenoid with a diode on it then that should work. You need to let the current flow from positive to negative but when releasing the button it just adds more in that direction, so a diode would not stop that. If your solenoid has only one wire and the case is grounded, then you cannot do that. You could try a diode on the power feeding the button as the charge could be arcing inside the switch just as you release it, in which case it would backfeed a little jolt through your power.

Do this first: Pull the switch out, and touch the 12v side (if its exposed at the solder joint). Then push the button and release it. If you get a jolt then the charge is arcing back over the switch and back to your 12v line. If you feel nothing then you have to isolate the solenoid and wire the switch the other way. Or perhaps get a source of power further from the head unit.

MustangBatman1

Hmm, as soon as I sucker someone into possibly letting me shock them I'll try it out. Thanks for the advice.

dkersten

LOL.. seriously at most it will make your hand twitch.. I was a professional car and home audio installer for about 10 years (about 10 years ago). The first time I ran into a situation where a relay was backfeeding power was in an old truck where he had a relay for some lights powered off a toggle switch mounted in the dash (metal dash). The ground for the relay was connected to the chassis of the toggle switch and the power ran through the switch itself. The switch was loose though, so every time I reached up in the dash and bumped the switch it clicked the relay, which sent the charge back through the switch body into the metal dash, only the switch was not grounded at the moment, it was my arm it was sending the charge through. My arm kept twitching with each jolt and freaking me out.. Finally I found the problem and tightened the switch so it would stop doing that. In that case my arm was directly touching the metal dash a few inches from the switch that was jolting me. Sitting in your car seat you wont be well grounded, but the jolt will still be noticeable if its backfeeding through the switch. The pulse will be too short to measure with a meter so just touching it will be the easiest way to figure out where the charge is going.

In any case, good luck with the problem, I hope you can get it fixed.

157dB

I beg to differ.
A diode properly attached to the coil WILL snub the PIV voltage.
Anode to Negative, Cathode to Positive.

jwog666

+ 1 on the diode, it will work. its the seame thing ford and to my knowledge every manufacturer puts on the ac compressor coil to prevent voltage spikes.

MustangBatman1

now for my noob question, how do I go about adding a diode and which type do I need? I did a search on radio shack and a ton of them came up with different ratings