I am trying to run down a parasitic drawl on my 84. I have isolated it to the CTSY/CLK fuse. It is drawing about 4.7 amps. Trouble is that particular circuit powers several things.
Does anyone have a method of figuring out how to do that?

 

I would unplug one of each of the things the CTSY fuse powers, at a time. I'd watch my meter in the process.

 

I suppose that I'll have to go through one system at a time???

 

Harbor Freight makes a tool that plugs in place of the fuse and shows you the amount of current flowing at that time. It is cheap and a very handy $15 tool when doing what you are trying to do. They make these devices with 20 amp rating for small fuses and they also have one for up to 30 amps on the larger size fuse.

Your parasitic draw should be ~35 mA is everything is working properly.

If you have a good multi meter you could install that between the battery Ground and the battery ground cable and use it as a ammeter. A lot of meters have a limit of 10 to 20 amps before they blow a fuse.

Either way you do it Tom400CFI is correct about unplugging each item, it is the easiest way to find the load. You could look in the FSM and find out what is on that particular circuit that could be drawing that much power. That would make the search a little easier.

Best regards,
Chris

 

You don't have to go through each system; You have to isolate each system. Put an amp meter in line (in series) between batt + OR ground and the + OR ground batt wire. You'll see your 4.7 amps draw on your meter w/the key off.

Then disconnect each item/cicuit on that fuse. Shouldn't take long, I don't think. You got:
DIC
Hood lights,
Horn relay
Courtesy lights
Door lights
Dome light timer
spare tire light
Cargo lights
vanity lights
console light

Cig lighter
Radio clock
Dinger/chime


That's quite a few things on one fuse, but you could get through it fairly quickly I'd think. I wonder if one of your lights is staying on; the console lights? Or one of the Vanity lights maybe?


.

 

You have to unplug each at a time to see which thing is causing the draw.

I'd suggest starting with the cig lighter.

 

Wish it had been the cig lighter. Turns out that the problem was the interior light delay board that was pulling all that electricical. Sucks because with out it I have no interior lights. I have had problems with that board before and replaced it about a month ago. Something is destroying it. The lights were still on but drawing too much juice. I'm still reading about 1.6 amps but I understand that that is acceptable.

 

I don't think that 1.6 amps is acceptable.

 

Also:
Power antenna
Power door locks
Bose amp relay (possible hum from speakers with radio off)

Are all of these items working properly? Something is stuck on, and probably not working as it should. A short circuit would draw more than 4.7 Amps, and would blow the CTSY/CLK fuse.

The normal current thru the interior lamp timer of my '84 is 3.15 A, with the courtesy lamps ON. My normal residual current drain is 0.013 A (13 mA).

 

Yep. I saw those...meant to type 'em....but then went ahead and NOT did that. Good catches though. I think the door locks would draw way more than 4.7A (but haven't tested them). Pwr Antenna and Bose amps are a possibility though.

 

I'm wondering if the power door locks can be disabled. I have not looked at the FSM electrical supplement to see about that yet. Any info on that is appreciated. It's funny but some of the stuff that is on the list doesn't work. No lights in the hood lamp, power antenna not hooked up. the passenger visor light never worked. The chime and console light are dead in the water.

I'm just barely above neophyte when it comes to the electrical system but I'm going to investigate the amp draw further.

 

First: 1.6 amps is way too high for the parasitic loss. Wow, 13 mA is pretty low, I have never seen a drain that low on a C4, that is a first. Thanks Hot Rod Roy!

Second: Check your power seat tracks, they can pull a bunch of current if the limit switch is off or broken. Disconnect them and check your current loss for any changes. The same for power mirrors....

Have you checked out the overall system yet? The fuses in your Corvette have Fusible links to be a last line of defense before the battery. I have found lots of corrosion at the connection post where the battery cable feeds the 12 Vdc power into the fusible links. On my 1988 C4 it is behind the battery under the side cover and is easily identifiable by the fairly large red wire coming directly from the battery Positive connection. I do not know where or if the 1984 C4's had this post anywhere near where mine was.
Measure the battery voltage with nothing "on" but connected to the car. The measure the voltage at your fuse box, they should be very close or the same. If not you have a problem before the fuse box then I would find the little connection post and make sure it is free of any corrosion. On my car the post were really badly corroded and caused a serious voltage drop (~2 Vdc) at the fuse box. After cleaning the terminals the voltage drop disappeared. I now had power at the fuse panel but not past that point.

Sometimes the fuses get a layer of corrosion on them that you can't see, On my car the fuses were all visually "Good" but there was nothing flowing through them. After cleaning the fuse block with a points file I installed new fuses and the power went where it was supposed too inside the car. Never assume a fuse is "Good" until you have tested it. My fuses looked brand new but had a layer of corrosion that impeded the flow of electricity. Cheap fuses were made of aluminum and they had a fine layer of white powder on their surface. I checked where the fuse is held and there was power there, it just stopped at the fuses which all looked perfect.

Check the battery voltage and then leaving the red lead on the battery Positive put the black lead on the engine block and again measure the voltage. These should also be the same. The engine needs a good solid ground to work properly. On my 1988 C4 there was a broken ground strap near my mufflers on the drivers side. After fixing it the antenna started working perfectly.

Power door locks can be disabled by unhooking the power wires. Frequently on these older Corvettes the door and lock mechanisms get frozen up with the old grease they applied at the factory. I opened up my door panels and spent hours cleaning the old stuff off and freeing up the parts. Afterwards you barely touched the switch and they would lock or unlock immediately. This is a good project if you have a garage or someplace out of the weather where you can clean the insides of the door panels. The old grease is like frozen solid and sometimes has to be chipped off.

I still stand by the tool from HF as it would make it easier to do for a non-electrical person. I would also check the Fusible links wherever they were installed on the 1984 Model Corvette. It sounds like your circuits are not getting any power so check your fuses as well.

You may not be an electrically oriented person but by the time we are done getting your car right again you will certainly know more then! This site has a lot of 1984 experts like Hot Rod Roy and Tom400CFI, these guys are still teaching me the differences in the 1984 Model over the later C4's. The experiences that you are tapped into here at the Corvette Forum is pretty amazing. There is a lot of knowledge and experience here to help others with the same passion for the Corvette!

Best regards,
Chris

P.S. Use the FSM electrical manual as it shows each fusible link and where it goes in your car. It is possible top have a bad fusible link, using pins on either side of a single fusible link and test their continuity. ANY Holes made in wires insulation should be sealed up immediately. I use electrical tape but a dab of silicone would do just fine to seal it up.

P.P.S. Check for wires that might have become so hot that their insulation is falling off. It is common as these Corvettes are know to run a bit hotter than normal cars. Check everywhere near the engine and behind it.

 

A lot to take in here Chris and I appreciate the reply. I will start on your processes and take things one at a time. I am concerned about the stability of the fuse box itself but to change that out is over my pay grade. I will clean the fuse contacts first. From what I've gathered the fusible links can be hard to get to. Will do some research.

 

You haven't said that your power door locks DON'T work, so I'm assuming they DO work. If that's true, the problem is NOT your PDL's. The only time there is any current thru the PDL circuit is when you push a LOCK or an UNLOCK button. And even then, the current is very low because you're only activating a relay. The power for the door lock motors comes from a totally different source. Your 4.7 A drain is not caused by your PDL's.

Is your antenna motor totally disconnected? If there's any question about that, remove the antenna relay, which is located under the plastic trim panel to the left of your rear hatch latch. That's a more logical source of your problem. The motor current IS supplied by the CTSY/CLK fuse.

The fusible links in the '84 are located at the battery cable post of the starter solenoid.

 

Thank you sir. I'll look at these. I had the starter replaced a couple of months ago.

 

Funny thing is going on. I mentioned that my meter was still showing about a 1.7 amp draw. I pulled all of the fuses again to see if one of them pulled out would show the draw but nothing happened with each fuse. When I close the doors that dropped to 1.3. I have left the meter on and it has dropped steadily to .3. I did disconnect the drivers side map light, mostly because the whole thing needs to be replaced anyways. I am going to leave the meter connected to the negative post and the negative connection today to see if this continues. Any thoughts?

Two hours later, down to .21 amps

 

Thing or two here. Check the well in the console with the seat switch to insure nothing is pressing on that switch DAMHIK. Turning off the radio 'should' power down the antenna to take that out of the mix. I had a parasitic power drain on another car, turned out the switch on the glovebox was broken so the light stayed on.

On the interior light relay, everything I've read says if you leave your doors open with the lights on, it will burn out the relay. I know there are relays available that don't have the delay timer in them, whether they burn out under the same conditions I don't know. Another I've read is if you pull the relay and connect the white wires together the interior lights will go on and off when the doors are opened and closed.

Just some thoughts.

 

I was chasing what I thought was a parasitic drain this summer (it wasn't). I extended my VM leads so I could put the meter on the windshield and close the hood, close the doors and watch the VM. It would take a couple/few minutes to drop down to .30mA but it wouldn't move from there after that. Seems to me mine would hang at 1.something for a minute or 2.

Because I was concerned about running the battery dead I put a negative battery disconnect on it which I would throw every time I parked it. After running the test a number of times over a few weeks I never saw evidence of a parasitic drain so I stopped looking for it but I often wonder if I have an intermittent fault though so far there's no evidence of it. With all the electrical/electronic BS on the C4s it's a wonder we can keep them running.

 

One more thought here. You realize that with the hood up or the door open you have operating lights. Are you taking that into account or have you disconnected them?