Topic: dead battery hood pressure switch
in Forum: C3 Electrical
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Joined: 12/3/2007
Posts: 292
Vette(s): 1978 Corvette Light Blue
Pulled from the swamps of Miami!
Its a driver and back on the road!
Ok I was trying to get the wiper botle pump fixed but now a new problem...I had removed the hood to make more room for the wiper bottle and horn and touch up of the engine compartment so I go out to the garage this morn to tackle the wiper resevoir water motor pump inop and turn the key to move the car and no turn... battery dead?????? ok so I am baffleded I did not ahve the radio on no lights no dome lights and never turned the key the day before while removing the hood this morn I have a dead battery so dont know how these are the only options...???
1. whenI removed the hood ther is a switch or vertical relay that the hood closees as you loer the hood located on the passenger side near the firewall still trying to find out what this switch does...
I thought it was a anti theft button or engine compartment light switch the light on under the hood not sure which but anyway with the hood off no pressure on the switch but no light either to turn on as it was on the hood that was removed, so did this drain the batery???
2. I notice the horn sounded funny so look at the horns after removing the hood and saw that one lead to the horn was off, so I put it back on and now both horns worked nice so I thought I fixed that problem of only 1 horn going off....
Other than that I did nothing or turned nothing on/off so ws it #1 or#2 that killed the battery I believe neither if the horn was shorting I would had heard something or the horns would not have worked and option #1 no light or alarm was working so the depressed switch which was not depressed with the hood weight missing did nothing???
your vote is needed or it was Murphy again... so charging the battery to get back to the water pump not working and then what killed the battery this corvette is fun if yo can quit your day job and have time ot work on it???
Thanks again BB78
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Oak Creek, WI - USA
Joined: 5/21/2008
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Vette(s): 1981 Great White Shark. Red Interior, 350/190 hp. PS, PB (SS), A/C CC, T-Tops. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vettes Car Club. 175,000 Original miles!! Now own a 1998 C-5!
There is a hood light on the Driver side of the hood which is on when the hood is raised. It is a mercury switch that "opens" the contact when the hood is closed. You may have killed your battery by not taking the switch apart. Thats where it is on my 81 anyway. Hope this helps
Dan
Lifetime MemberManteca, CA - USA
Joined: 11/20/2005
Posts: 3623
Vette(s): 1978,two tone,Metalic Rootbeer & gold
1975 L48 4 speed
Is it possible that you haven't been driving enough to maintain the battery and it just slowly discharged. If I don't drive mine regularly the batteries will run down and then one morning, no go. Of course it should depend on how long you let the motor run each day if you're working on it. These cars all seem to have a slight drain on the battery, wether it's a clock or ? hard to say.
Jimmy B.
Just can't wait to get on the road again. 
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
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#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The alarm system pin-switch is on the pass side of the firewall. With the hood closed, it opens the switch, which kills the ground to the alarm system. The only way leaving the hood open(or off) could cause the battery to go dead is if the alarm system is armed. You may have a bad relay that is causing it to stay armed all the time, and when you took the hood off, it was like the alarm going off constantly, until the batt went dead. If the alarm horn is bad, or unplugged(or missing altogether), you'd never know the system was armed....
The underhood light is a simple mercury switch, built into the lamp assy. Once you unplugged it to remove the hood, there no way it could drain the batt, unless you pinched the wire for it....
I'd bet on the alarm relay, unless your alarm is working properly, which is kinda rare, but it does happen!
btw...I'm not sure if the underhood light comes on unless the headlights or the key is on anyway. Does anyone else know for sure that the underhood light will come on just by opening the hood, without the headlights or the key on?
Adams' Apple 2009-07-13 12:07:33
The underhood light is a simple mercury switch, built into the lamp assy. Once you unplugged it to remove the hood, there no way it could drain the batt, unless you pinched the wire for it....
I'd bet on the alarm relay, unless your alarm is working properly, which is kinda rare, but it does happen!
btw...I'm not sure if the underhood light comes on unless the headlights or the key is on anyway. Does anyone else know for sure that the underhood light will come on just by opening the hood, without the headlights or the key on?
Joel Adams
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Oak Creek, WI - USA
Joined: 5/21/2008
Posts: 1965
Vette(s): 1981 Great White Shark. Red Interior, 350/190 hp. PS, PB (SS), A/C CC, T-Tops. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vettes Car Club. 175,000 Original miles!! Now own a 1998 C-5!
The underhood light comes on regardless of the position of the light switch. If you raise the hood, the light will come on ! (Unless you take the bulb out of the socket). !!
Dan
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Vette(s): 1978 Corvette Light Blue
Pulled from the swamps of Miami!
Its a driver and back on the road!
Thanks Joel and Dan
I thought the alarm switch might be it but since no alarm was going off not sure how you arm or disarm it but thought that will not discharge the battery but like yo say tif the alarm horn is not working then ok it would not signal??? and the light i had removed so it could not or should not be draingn the battery, unless it had a short in wiring but never drained before... I had removed the light to fix on the hood so that should not have been it but prior I could not ge the light to work either so thought no drain there... I believe its the alarm switch being up or open and no horn working so it drained the battery with no hood on to compress the switch..thanks again for the info and you say the light should come on opening the hood but what trigers it is the switch is the alarm switch and not the light switch?/and also what arms/disarms the alarm no key outlet by the corvette flag like earlier corvettes??? Thanks again will check out.... but got the regular horns(both working ) just have to get the hood back on!!! BB78
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The alarm is activated by the door key when the door is locked with the key. I'm not sure if it will arm the system by just using the electric locks, if your car has electric locks. There should be a switch inside the door(s) taht operates the alarm system, as far as turning it on/off. If your systems is staying armed all the time, the problem could be the door switches, but there have been more issues with the alarm relays sticking than anything else....
Joel Adams
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Joined: 12/3/2007
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Vette(s): 1978 Corvette Light Blue
Pulled from the swamps of Miami!
Its a driver and back on the road!
I am new at this corvette thing, and not sure on the alarm, trying to get info on it, I do not have a key by teh driver emblem for the alarm switch (78) so not sure how to arm or disarm the alarm... If it is the drivers side key door lock then mine is inop that is the next project the key will not lock or unlock the door I have manual locks so I will be takig the inside doors apart time permitting to fix the locks and get the key working again but not usre if I have the alarm until I invetigate... so dont know if it is armed and the horn inop, or not working.. so when I removed the hood it triggered the alarm but horn inop I'm not sure...Thanks again for the info time permitting I will get it corrected with the right info..Thanks again BB78
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Joined: 12/3/2007
Posts: 292
Vette(s): 1978 Corvette Light Blue
Pulled from the swamps of Miami!
Its a driver and back on the road!
Thanks for the info, figured it must be the alarm relay thats open/close when the hood is up but stil not sure. Even if its saying the alarm should be going off and the horn is inop or wiring bad or I would hear it, unless there is a short and power not getting to horn or the key on/off is shorting.
The door panels are coming off next then I will be ablt ot check the door entry alarm switch if its there??? and check for shorts... Still the hood ot up all that long and not thinking its taking much power but If shorting maybe??
I had the hood offo to do some touch up on it and new insulation pad, etc... but also trying to get the washer bottle out and check if the washer pump is bad or wiring but still trying to figure that out, i see the horn is behind/beside the washer pump so if I get the bottle out can check the horn also.... They both have the coded yellow/orange wires but lead into the firwall grommet and need to try and trace them inside.(good simple wiring chart would help?) but maybe both are related wiring to horn and washer pump... The door locks are not working at mentioned they are manual door locks and this will be checked on the next project???? soon I hope. Thanks again for the info.
Dan also mentioned the light comes on when yo raise the hood... Mine is not but I see the wiring has no power in it so tracing it also but what triggers the light..Wher is the switch or is it using the alarm toggle also when hood is up???? ok enough time to go for a ride. Thanks BB78
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Joined: 12/3/2007
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Vette(s): 1978 Corvette Light Blue
Pulled from the swamps of Miami!
Its a driver and back on the road!
Hi Dan (Mercury Switch) is this the same switch under hood that the alarm is triggered by or another switch, that opens when the hood is raised. I have wiring problems to the light no juice, but hooked the light to a 6volt bater and with the pos/neg connected it works, so the bulb holder and wires are making contact and work, just got to get juice to it... But if I hook the main wire to the pos battery and the other wire shows to the bolt holding the lamp in place i assume the ground the light will not work, how is the neg wire getting metal contact in the fiberglass hood unless the screw is grounded somehow... but the light will not come on with pos to bat and ground wire connected to the lamp screw, so maybe I have a grounding problem also horn related???? There is only one wire coming from the harnest to the bulb which has a little cannister inline but the other wire from the light I dont see how its making the circuit to light the bulb???Thanks again???BB78
in Forum: C3 Electrical
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