I found the conversation on another forum...here is how it went...
Scored a lamp timer module from a destroyed '86- Then I pulled the board out and someone already let the smoke out of the diode (D1). Mr junkyard man gave it to me, so its time for scientific experimentation!
Unless someone knows what the number USED to be on the part?
Eckler's had the 84 courtesy lamp timer for $25.99 (their # 39434), but it has been discontinued. I will check with my contacts here for the part.
I hacked out the part- turns out to be a 1N4005 (print was on the non-blown side). Got a new one at Radio shack. I am replacing the electrolytic. cap as well.
Smoke check coming soon!
Replaced the diode and the cap. Plugged in the part -cringe- sloowly open one eye...courtesy lights are on, no smoke.
Cool.
Push the hatch release button on the door -pop- hatch opens (It never did that before without turning the headlight switch CCW)
So at this point tempting fate, I closed both doors and the hatch.
The lights stayed on....still on.....continued on......off- Yay!
The other guy with an 84 in the vette club demonstrated how the lights gradually dimmed instead of clicking off- is this just an '84 thing? (my module is from an '86)
The courtesy lamp timer on my 82 ce slowly dims the lights as well.
Interesting, I also found the diode in my 84 module is rated at 60v reverse current, and the one that blew up in the 86 module is rated 600v...time to swap that bit then experiment some more.
Yes, and the C3 (orange) and C4 dimmers (black , early C4) are interchangeable. The circtuit board inside is almost identical, the case is different. The only thing is that onn the c4 the tab for the connector is on the other side so when using a c3 one in C4 or vise versa you have to push the conenctor in w/ the tab on the wrong side. It won't snap into place but it'll be tight enough so it won't come loose. I have the early C4 one in mine.
You meant to say "reverse VOLTAGE"....didn't you. heheheh
I highly doubt that at even at 60V the reverse-bias voltage is what blew it...more likely the forward current, all of the 4001-4007 diodes are rated at 1A continuous forward current.
Do you still have your original timer?
I stand corrected, (geez I shoulda been tipped off by the units..duh) But that's why I'm a technitian, not a real engineer (Thanks for the opportunity to put your work to use! hee hee)
The '86 one was easy to diagnose due to obvious damage to the diode-probably from a short. The car it is from was destroyed/rolled/bent&spindled.
I do have the original one, it does not have any smoke-checked parts thus complicating the diagnostics. I think the dimming function is cool so I would like to restore it. Any insight as to what part failed?
Well I've never looked inside one. I could take mine out and see what the guts consist of...or you could send me your old one if you want.
If you have any questions, look for GeekyBill on this forum...he is included in the conversation above.