grasshoppertym

my battery keeps going dead on my 87 iroc 305 auto
i replaced the fan relay switch as it looked a little crispy, but battery still going dead. can anyone tell me where the fuseable links are and how to test them to see if they have blown. i have only had the car for about 2 months now and it never did this to me until about 2 weeks ago now, so i know it is something recent that when wrong, but i have racked my brain looking around but there are alot of wiring under the hood. and wirth ac and dual fans and tuned port injections i`m not sure where everything is
if you could help that would be great and if you have pic of fuseable link that would help me out too
mike

x11nt4

I used an 87 TPI harness for my swap so my info may help as far as fuseable links go, but it seems like there was a couple that came from the back of the alt. These I cut out and put real fuses in their place. Older GM cars in the 70's had links right at the bulkhead connector - engine side which makes them a REAL PITA to work on. I doubt it's a link. They blow to easily.

Can you give an idea of how long it takes to drain the battery?

grasshoppertym

not sure exactly but it is definatly less than 24 hours, and when i put my charger on the battery when it was still in the car it didn`t charge well which was my first hint there was a problem, and when it finally showed full charge it was only 1 or 2 min before it turned on again to top up the battery....on...off....on...off
after i changed out the fan relay i re-installed the battery and again the next day dead. so i have had the battery out of it until i have time to look it over which hopefully will be tomorrow night. i think my computer is fried so that might be where the short is but i want to check any other possibilities before i buy a new computer incase it gets fried from what ever short is causing my battery issues

x11nt4

Does the car not run at all? If the ECU is fried then it would not run at all.

It is normal for chargers to go on and off, that is how they maintain a trickle charge to the bat. 1-2 min is not bad at all. If it was every 10 seconds, then I would say there is an issue.

How old is the battery? It might be as simple as an old battery that can't hold a charge anymore. There are internal shorts in the battery plate that develop which would cause a lack of capacity / run time. The side post terminals are terrible for corrosion. It happens a lot that you will get buildup between the post and the battery causing it to never get a good charge from the alt. The alt wire to the bat may have excessive corrosion built up into the cable which will also prevent good charge.

The only way to really test if you have a problem with the car is to do a parasitic load test. See how many mA or A you are drawing at rest with everything turned off. Some load is normal, say in the 15-30mA but if you get into the 1/2A range, there is something causing a high drain.


Some of the more stupid things that happen is, vanity mirror lights don't turn off ( on the visors) a glovebox light is on, the light in the rear hatch is on. Just things like that.

The more serious things I have seen can be the VR in the alt has gone bad and is causing a short. The alt may still work but it kills the bat after a short time. The starter solenoid may have a slight short in the windings.

grasshoppertym

the battery is brand new, and was holding a charge fine up until the day i fixed my hatch pull down motor. 5 min after i put it all back together i went on to the next task of checking my engine code (as the light is always on when the car is running but it will not light up if the key is on but not running and others on this site seem to think that means that the computer is no good or the grounds are no good for the computer), and the battery was dead. the car runs but idels too low and i have to keep on the throttle to keep it running until it warms up for about 2 mins and then it will idle fine for several mins and then it snuffs out and won`t want to idel until it cools down for awhile. all i have done is run it in the driveway as i have not had it for too long and am fixing up a few things before i take it for the saftey inspection

x11nt4

You say you fixed the hatch motor... You know, you might want to go in and unplug that motor just to see what happens.

As far as the computer goes, yes it is a grounding problem, but that is not the source of the short, nor would replacing it cause a problem before finding your issue. i know cause when I did my TPI swap, the computer I got with the harness did the exact same thing as yours is. It is a grounding problem inside of the computer, but there is a ground wire that attaches to the firewall behind the engine that feeds the computer ground so that might be where your problem is. But in my case, the ground was on and the computer did what yours is, went to AZ, got another and that fixed that issue. Dirty secret is, you can swap the board inside the computer, then take it back. Those guys at the counter won't know you did it. Just FYI

paulo57509

Hatch motor? Does your car have that little light in that panel that covers the motor? I'm ALWAYS forgetting to turn that light off = dead battery.

mrrman

marked as I have a similar issue in my 87 TA...I started by replacing all my gnding cables, alt and battery cables...new battery installed and still have the same problem...

x11nt4

I was thinking too, perhaps that light, if you had to remove it perhaps it got buried behind the cover some where and is on and you just can't see it? Also I was wondering if you have power locks? they are a large solenoid that engages the lock on the doors and the hatch. Perhaps one of them is staying energized, not switching off once it is locked / unlocked, and causing the drain on the bat. These would be pretty power hungry. It seems like if your battery is completely dead with in a few hours, it would have to be a pretty good A draw on the battery, 10A-15A or so would be my guess. A bulb would not do that quite that fast. A couple days, sure but not in a few hours. I guess if it is a big bulb. I have had the doors open and the radio blasting for several hours on my bird and the battery was a little weak but not dead to the point the engine would not crank or start. I have 3 lights total, dome and 2 kick panel lights that come on with the door open. I have left a pair of driving lights on before and after 4 hr the car still started.

A power window motor not shutting off after it is rolled up? That would be a big drain too.

x11nt4

I had one last thought for the night. Perhaps this is a stupid thought, but have you thought to check your headlights were not on even when they are retracted? It's possible they are staying lit even though the covers are down.

grasshoppertym

i am going to look over the hatch motor tonight, and i will check the cargo light but i am pretty sure it is not the problem cause right after i put all my interior back in the trunk the battery was already dead, i will try pulling the power on the motor adn see if that fixes the problem. i did check the ground on the firewall and it looks good, i pulled down the emc and looked for more grounds but found none. my headlights are not on and the only thing that i know stays on whitht the key in the on position is the fuel pump cause the p-o wired it direct from the fuse pannel for some reason, my fan turns on when the key is in the on position sometimes too, have 1 more fan relay to change tonight will i am at it so hopefully i figure something out tonight

x11nt4

The fuel pump should be going to the relay on the firewall/driver side, and is cycled by the computer. That is an interesting find, makes me wonder what other shotty half-assd electrical work was done to that car b4 you got it?

This may be a long shot but when ever I see things like that I suspect that is where my issue could very well be. Hard to say though.

Like i said though, a parasitic load tests is really the only way you will know how much A draw there is which would allow you to then start with the most likely candidates for issue.

Personally, I would get the meter out, 20A would be best but a 10A will work, check for amp draw on the bat, then start pulling fuses in the panel and see what the changes are. If you get through all of the fuses and CB's in the the fuse panel, and the A draw has not changed significantly, then it is a sure bet it is not anything in the interior of the car. Unless something has been creatively by-passed from the fuse panel.

I can check my bird out for you and see what its parasitic load is just so you have an idea of what it should be. They should be pretty close, as the computer and radio memory are really the only 2 things that should draw a parasitic load.

grasshoppertym

YA IF YOU COULD CHECK YOUR DRAW THAT WOULD BE NICE, I HAVE AN AFTERMARKET STEREO SO IT MIGHT BE OFF A LITTLE BIT BUT SHOULD BE CLOSE
I AM GOING TO CALL MY DAD TO GIVE ME A HAND WITH THE TESTING TONIGHT TO MAKE THINGS GO A LITTLE QUICKER

x11nt4

Ya I have a sony in mine also, but I do not have any amps right now so that should still be fairly low. Just from what you are describing the draw acts as if you left your lights on all day ya know? That's the kind of draw that would pull the bat down in the time you are talking, so something in the car as to be pulling a similar draw.

x11nt4

BTW, have to looked at the cable to the starter? I once had an issue on my 74 camaro that the battery cable had come in contact with the header and the insulation melted down to the wire. It did not cause a dead short to ground, but it was enough that it killed the battery in a very short time. Might be worth taking a peak at to make sure the same hasn't happened to yours. I have seen a similar condition happen also if the bat cable is touching the frame and has worn a hole in it. Just a thought.

grasshoppertym

so i replaced the other fan relay before putting the battery back in, but the fan still turn on as soon as the key is turned to on, so maybe it is a computer or sensor problem telling it to turn on. i checked all the interior lights including the hatch none were left on. i opened up the hatch panel and checked over the hatch pull down motor and everything looks ok but i dis-connected it anyway and left the battery in to check if the battery goes dead overnight. one other thought, i was wondering if the hatch pull down motor didn`t go all the way down till it clicks into reverse (and stops) would it still draw power until the battery went dead? i did notice that it doesn`t click at the bottom of the stroke unless i lean on the hatch. if the battery is not dead tomorrow i will hook it back up and try test that therory. i ordered the new ECM tonight so i will hopefully have that to install early next week and mabe all my problems will be solved.....ya right but heres hoping

grasshoppertym

SO MY BATTERY STILL HASN'T GONE DEAD SO I GUESS I FIXED THE PROBLEM, BY DISCONNECTING THE HATCH PULL DOWN MOTOR...OR DID I? WHEN I DISCONNECTED THE MOTOR I JUST UNPLUGGED THE LITTLE BLACK BOX (RELAY?). MY HATCH MOTOR STILL WORKS LIKE IT SHOULD WHEN IT IS UNPLUGGED AND MY MOTOR IS NOT WARM TO THE TOUCH ANYMORE. I NOTICED IT WAS WARM WHEN I WAS DISCONNECTING IT BUT I HAD JUST RAN IT UP AND DOWN A FEW TIMES SO I DIDN'T THINK MUCH OF IT, AND NOW AFTER RUNNING IT UP AND DOWN A FEW TIMES WITH THE BLACK BOX UNPLUGGED IT IS NOT WARM AT ALL. DOES ANYONE KNOW WHAT THE LITTLE BLACK BOX IS FOR? I AM GOING TO JUST LEAVE IT UNPLUGGED IF IT IS NOT FOR SOMETHING ELSE, IF I NEED IT I WILL REPLACE IT BUT WHAT DOES IT DO? SORRY ABOUT THE CAPS, I HAVE TO USE THEM AT WORK AND I FORGET TO TURN THEM OFF
MIKE

x11nt4

Does your hatch have a power lock?

grasshoppertym

MY CAR DOES HAVE POWER LOCKS, BUT ISN'T THE HATCH ALWAYS LOCKED UNLESS YOU USE THE KEY TO OPEN IT OR THE SWITCH ON THE CONSOLE TO RELEASE IT? UNLESS IT LOCKS OUT THE HATCH SWITCH ON THE CONSOLE WHEN YOU HIT THE DOOR LOCK BUTTON I DON'T SEE THE POINT OF HAVING A POWER LOCK ON THE HATCH BUT I DON'T KNOW HOW THEY BUILT THEM. SO YOU THINK IT IS THE POWER LOCK RELAY?

x11nt4

I can't say for certain, since my fbird does not have this option, or even a provision for it. I have not seen this on the cars I have gone through in the j/y So my answer is purely a guess, based on what would make sense.


I would think ( if it is a relay, perhaps you could take a pic? and where it is when it is in the car? ) it would be a relay for the motor itself, like the headlights have, but since you said the motor works w/o the relay, that makes me think, assuming the motor is not bypassing the relay some how, that the relay is controlling something else when the motor is running.

I would have to think it has something to do with the hatch lock/latch. Does this motor only close the hatch or does it assist in opening it? I know you have the struts to open the hatch but I am just curious if it only closes the hatch.

In any case, it would seem to me that the relay would automatically lock the hatch once the motor reaches it's closing point, then engages the lock. I would also imagine It could keep the latch "open" till the hatch comes down, then the relay engages and closes / locks the latch. Just a theory at this point though.

Why the box is killing the battery? who knows, If it goes to the hatch lock, perhaps there is a short in the hatch lock solenoid itself? IDK, pure speculation at this point. If I have time perhaps I will look at the diagrams on mitchel on demand and see what it shows. I would be curious to know too.

grasshoppertym

THE MOTOR PULLS THE HATCH DOWN AND SHUTS OFF AFTER HITTING THE REVERSE SWITCH, WHEN YOU SLIDE THE BUTTON TO OPEN THE HATCH IT UNLATCHES AND THE MOTOR MOVES THE HATCH UP AND THE MOTOR SHUTS OFF AGAIN WHEN IT HITS THE REVERSING SWITCH AGIAN.
WHEN I PUT IT BACK TOGETHER I WILL TRY AND REMEMBER TO SNAP A FEW PICS FOR ALL TO SEE, BUT I MIGHT NOT GET TO IT FOR A FEW DAYS. IF IT IS NOT THE LITTLE BLACK BOX THAT WAS KILLING MY BATTERY, IT MAY HAVE BEEN THAT THE MOTOR WAS NOT SHUTTING OFF WHEN DOWN IF IT DIDN'T HIT THE REVERSE SWITCH BUT DIDN'T HAVE ENOUGH POWER TO PULL DOWN THE HATCH ANYMORE. I MIGHT LOOK INTO ADJUSTING THE MOTOR UP A BIT TO MAKE SURE IT IS NOT OVERTIGHTENING THE HATCH AND BURN UP THE MOTOR FOR NO REASON.

THE HATCH PULL DOWN MOTOR ASSEMBLY CAME OUT OF MY OTHER 87 Z-28 I HAD AND IT WAS NOT EQUIPED WITH POWER LOCKS, BUT I CAN NOT REMEMBER IF THE LITTLE BLACK BOX WAS ORIGINALLY FROM MY CAR WITH POWER LOCKS OR NOT. I'LL GET THOSE PICS MAYBE TOMORROW NIGHT IF I HAVE TIME. THANKS

x11nt4

Ya, I think at this point from what you are describing, that would be the going theory here. Usually power locks to have a relay, again without having either feature on mine I can't say in the rear hatch lock would have a relay for sure, but it probably does, whether that is the relay or the relay would be under the dash or in the cargo area near the lock, who knows at this point.

IF the motor was not shutting off, that would definitely cause the kind of current draw to kill the battery with in a few hours. I would guess the motor probably is at least 5A draw, maybe more. The reverse switch you mention could be a little bit dirty and sticking, or perhaps worn out a bit. But I think it is safe to say you have found the dirty skunk in the wood pile here. Just a matter of, if its the motor, or the switch keeping the motor on and just needs adjustment or cleaning. You might see if the hatch unlocks with that relay out. That would tell you if that is for it or not.

Good luck!

grasshoppertym

IT DOES UNLOCK THE HATCH WITH THE RELAY OUT AND IT LOCKS BACK UP WHEN CLOSED SO I THINK YOU ARE RIGHT IT IS A RELAY FOR THE POWER LOCK, I DON'T HAVE THE KEY FOR THE HATCH OR THE DOORS SO I CAN'T TRY THE KEY TO SEE IF UNLOCKS/OPEN THAT ROUTE. NOW TO INSTALL THE NEW ECM AND SEE IF I CAN FIGURE OUT SOMEYTHING FOR MY DOOR/ HATCH KEY
THANKS, MIKE

grasshoppertym

so i put it all back together tonight but i did snap some pics before hand
but not sure how to post them on here. other bad news is that i put my new computer in tonight too and now it runs even worse at idle (maybe a relearn issue ) but my ses light still doesn`t come on they way it should
so i think it might be the prom but at this point i am close to giving up abd take it to the shop and let them figure something out
i think i figured out how to upload pic lets see

x11nt4

Is this IROC a TPI or TBI car?

TA-Rocks

I have a suggestion: If you take the fuses out one at a time and test the circuits with an mpmeter then that should give you an idea whats going on. I would put the meter between the fuse terminals on amps on a VOM meter, then test for higher currents. With everything shut off you should be getting very little current. Actually just removing the fuses should remove the short trouble. BUt to know which one will take some trials. Just an idea. Hopefully it can tell you something.

grasshoppertym

IT IS A 87 IROC 305 TUNED PORT INJECTION WITH AN AUTO TRANS, ALL STOCK

grasshoppertym

I THINK I GOT THE SHORT ISSUE SOLVED, I BELIEVE IT WAS THE HATCH MOTOR NOT REACHING THE BOTTOM OF THE STROKE AND TURNING OFF, IF I LEAN ON THE HATCH IT WILL GO DOWN ALL THE WAY AND CLICK THE REVERSE SWITCH WHICH SHUTS IT OFF, I HAVE HAD NO DEAD BATTERY ISSUES SINCE. I WILL SEE IF I CAN ADJUST THE MOTOR UP A BIT SO IT DOES HAVE TO PULL IT DOWN SO HARD

TreeFiddy

You haven't by any chance removed your rear spoiler, and also put in new hatch struts? I have, and the poor old hatch motor just doesn't have the power to close the hatch against the pull from the struts, without the weight of the spoiler to help.

It will just stall like it sounds yours is doing, and continue to draw current until either a fuse pops or the battery is flat. Though I never let it get that far, can't be good for the motor.

Like you, I just lean on the hatch till it clicks. This will be fixed if I ever get around to replacing the spoiler.

grasshoppertym

nope, never removed the spoiler or replaced the struts, i just installed another (not original) hatch pull down motor. when i bought the car the original was removed

TreeFiddy

Yeah long shot. Like you said, sounds like the motor's not quite adjusted to the right position.