First post here - hope to have many more positive ones. I am at a loss. I have found that my 1976 Corvette with power windows, auto tranny and A/C (removed) had a short and was draining the battery overnight. It all started with the power lead from the starter to the alternator and bulkhead rubbed against an engine bracket. Replaced the engine compartment wiring harness. The short then led me to the courtesy lights / lighter / clock and with the replacement of the dash wiring harness that mostly solved the issue. (when doing the trick with the test light connected to the battery terminal and attached to the battery cable to produce a dull glow) I traced it to the rear wiring harness to this corroded relay that was located in the rear passenger right next to what looks like a turn signal flasher in the same compartment. When I pull the relay the light goes dead as it should be. In going to the parts store they handed me a horn relay, but when I hooked it up it blew a fuse that I had installed in the power lead from the starter. Please help - thanks in advance  


RELAY PIC

(modified huge pic to link-aapple)


|UPDATED|6/14/2015 8:39:24 AM (AZT)|/UPDATED|

do it the easy  way  before going crazy  install battery cutoff switch  I have had problems for ever so I installed cut off allswell   I have the same battery for 3 years now   dwa

That is the Alarm relay. It is NOT a normal relay, in that it is a "latching" relay. Once the alarm is activated(door/hood opened), the relay will stay engaged until power is cut to it, by turning the alarm system off with the keyswitch on the fender.Closing the door/hood will not turn it off.

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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thank you so much for the information. Now all of this is starting to make sense. The previous owner put a Grant steering wheel into her and did not hook the horn up - for good reason the thing is going off constantly! The sensor for the hood is just dangling by the wayside indicating to the system that the hood is up... therefore the relay is on all the time draining the battery. The car starts and runs but once I pull the relay I loose ignition. She will crank - but no spark. So.... how do I bypass the relay? 

I would rather see you fix the horn and the switch. But if you just disconnect the relay your problem at hand will go away.

I see the point - however i have the security key in the "off" position yet the relay is still tripping as if its armed? I am simply tying to make it to the point that I don't burn it to the ground (the relay gets really hot!) but I have a mess of engine and other items that need fixing. I would rather work on it and not worry about draining the battery or burning it down in the meantime.  

put in battery cutoff switch

Dumb question: are you sure the alarm switch is in the off position?  For many years I thought vertical was off, but off is actually horizontal.  Wasn't a problem when the system didn't work at all but after I started messing with it to try to get it working again, I got battery drain.  I have a battery cutoff switch but it's easy to forget and with the drain that the alarm system causes, it would drain in a day or two - not good.  Better to fix it right or completely disable the system.  I did get it working eventually with a fair amount of tinkering.  I now have a functional factory alarm system that I actually use (although it is quite rudimentary compared to modern systems)  One of the most problematic parts of the factory system is the switch piggy backed on to the key switch that will trip the alarm system if someone tries to mess with the key switch.  Very finicky and if it's not positioned correctly, it will trip the alarm.  IIRC, that switch is the same P/N as the headlight warning switch (the one that will make the dash light come on if the headlights don't come up all the way).  Also I had trouble with the door switches - be careful with cheapy replacements.  

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Daveo76 - excellent point! It was in the vertical! I only assumed that because someone had installed an aftermarket alarm system that was activated when the key was horizontal. (unfortunately a good portion of the wiring and other systems were hacked in the last 20 years by people trying to patch it together to keep it running. I don't understand the logic of mounting a $250 Autometer Tach in front of the original when you can get the new circuit board for $65. But that's the type of previous owners.) I've spent the good part of a month taking out hacks like that one. Now if I can only get the wiper motor to work properly...

Hunyadii - welcome to the site, and you now have met a very popular guy we refer to to as "Bubba". Bubba has done all kinds of "fixin" on these cars and I wish you the best of luck if Bubba's been "fixin" the wiring in your car. Keep up the good work.




|UPDATED|6/15/2015 8:56:51 AM (AZT)|/UPDATED|


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John Sigmund

That makes no sense....
Nothing on the '76 factory alarm system is tied in with the ignition system...it simply beeps the alarm horn. You mentioned that Bubba had also wired in an aftermarket security system....that's where I would start looking for the problem. He has tied into the factory alarm system somewhere that is powering the ignition feed thru the factory relay...not a good idea at all. Thass prolly why the relay is hot all the time.... As far as bypassing the relay....we'd need to know HOW the ignition is connected to it to help wid that one...  It's possible he's tied the ignition feed into the fenderwell keyswitch.....

If you don't have the Factory Service Manual,  you can can view and/or download the wiring diagrams from my web page. You'll need to click on the '77 diagram to get the Alarm system diagram, but it is the exact same system/diagram.


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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Glad to help.  I forgot to mention in my first post why the alarm was tripping and draining the battery and I didn't know it:  the alarm horn was not working then.  It took me removing it and cleaning it and the contacts before it started working.  Getting to the alarm horn is a PITA - way up above and behind the driver's side rear wheel.  

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