Rep Power: 291

I have seen schematics for headlight relay harnesses showing a diode across the coil terminals of the relay. i never saw the need to put them in. now i know that there's significant data out there that shows that when a relay de-energizes, the energy stored in the coil has to go somewhere and it can spike the voltage of the system.

so i have 2 relays for my HID retro, one for each ballast. about a year ago, i started noticing a click when i turned the lights off that was coming from my stereo. as the relays got some age on them, the click turned into a thump from my speakers and my sub.

so i put an oscilloscope on the 12v (all relays and ballast power coming straight off the battery) and it measured a 38vdc spike when the relays turned off and the ballasts shut down. i thought it might be the ballasts, but those disconnected and i was still getting the spikes.

so i bought some $4.50 relays from Mouser/Newark that had the suppression diode built in. no more thump and no more voltage spikes.

so what's the point of all this? well, after a year of voltage spikes everyday, my Kenwood sub amp stopped working. it was going into protection mode. after i got the diode relays, i bought a new amp and life was good. today i got around to opening up the amplifier and the pic below is what i found (2 fried transistors). moral of the story......spend $3 more than the $1.50 relays and get some with diodes so you don't fry your electronics.

 
Rep Power: 245

from all the wiring and electronitc guys out there.......

DUH!!!

if it's a mecanical switch then u can decide to omit it but NEVER omit it on electronics.

 
Rep Power: 291

i took it forgranted because the 24v relays i use on automated machines all have them built in standard. most automotive relays don't have them though. you have to make an extra effort to locate ones that do. you walk into any auto parts store and the cube relays they sell for fog light kits don't have diodes.

 
Rep Power: 291

Is the amp fixable?

 
Rep Power: 812

yeah its one of those things most people are too lazy to implement. there are alot of other relays on the car stock, i wonder if those have suppression including the stock headlight relay. ive heard of headlight switches frying because of current back flow. i ran various hid setups for a year and never had a problem, but im sure its doing some damage somewhere.

 
Rep Power: 291

might have been the combo of relays and ballast i had?

 
Rep Power: 291

probably. visibly, there's just the 2 transistors. there could be other components bad too. the amp is over 7 years old, so is it worth the time and money to repair a 300w 7yr old amp? not to me. i threw it in the trash and bought a JL Audio G1300 amp.

 
Rep Power: 0

Good show&tell! That splains the installation I saw where one sie of the diode had broken off the relay terminal & everything still worked fine. I asked the guy who installed it what the diode was for. Whatever he said didn't tell me a thing (no speeka de lingo) but i soldered it back on figuring there hadda be a reason for it. Thanx!

 
Rep Power: 291

here's the link for the relays i bought:

http://www.mouser.com/Search/Product...9-CB1F-D-M-12V

 
Rep Power: 812

thanks for the link, but they say its out of stock with 2 month lead time. any other place to get these?

 
Rep Power: 812

would this work? seems like the same thing but without mounting hole

http://search.digikey.com/scripts/Dk...me=255-2159-ND

 
Rep Power: 291

yep. that will work too. just needs a diode built in between 85 and 86

 
Rep Power: 291

link is back in stock

 
Rep Power: 812

i ended up getting one a while back but threw it away due to something with it causing my hid lows to flicker when switching to hi beam mode. not sure how or why, but my tyco relay never did this so i went back to it. i guess i will change the headlight switch if it fries from voltage spikes.i have no stereo so i doubt anything else would be damaged.