Electrical issues non start and low voltage message

F

Firepit

Well-known user
I'm experiencing some electrical issues. I've had the ignition switch changed few months back after getting "charging circuit fault" messages on starting. (its contacts where quite burnt) I put a new red top battery on in April this year and I've had most of the earthing points cleaned up.

So after all that everything was fine for a couple of months until yesterday when I came to start the car. (It's been on a good quality tender but not started for about 4 weeks). It tried to turn over very slowly and then died, after that just the clicking noise. I tested the battery and it was around 11v, (odd as it has been on a tender) so I took it off and put back on the original yellow top which I still had. that one did barely start the car and after which it ran fine, the alternator was working and charging because the dash voltage went up to 13ish volts. I've got that yellow top battery on charge now also disconnected from the car and so I'm expecting it to be ok for testing again later.

My question though is related to a difference in the actual battery voltage and what the dash shows with the ignition on. Should there be a variance?

I'm guessing my next quest should be to find out if I have battery drain of some kind. New multimeter on order.
 
oelarse

oelarse

Well-known user
The voltage shown in the gauge in the dash is measured after the ignition switch . Since the ignition switch is recently replaced it should not be any voltagedrop due to burnt contacts and the voltage measured over the battery should be
equal to the voltage indicated in the dash gauge . But I think the accuracy of the gauge is lower then a multimeter ( I only trust the values on my multimeter :)) .

The drain current should drop from 8-10 amp. down to 25-30mA after approx 15 min ( mine is approx. 29mA)
If you connect the meter in serial on the NEGATIVE side of the battery on 10 a range it could be done like this

If you observe an excessive current then you can measure voltage ( mV range on the multimeter ) over each fuse in the engineroom and in the fusebox in passenger footwell to locate the fusecircuit containing the bad component
If you look through this video it will show how to
Here is a link to charts showing voltagedrops for the different fuse sizes and fusetypes
 
F

Firepit

Well-known user
Thanks for the advice and the links. I've watched the video through and I'll print the charts out. Some of the directions say to pull the fuses one by one which is what I was going to try. I do like the idea of quickly reading each fuse via this method though. Unfortunately I've got to go to Santa Clara next week so I won't have time to do this for a week or so.

Thanks again very much appreciated.

Paul.
 
F

Firepit

Well-known user
Nope, not had a chance. Although I did pop the original yellow top back on and left it on the tender for a couple of weeks while I was away. When I started the car last weekend it did start but laboured a bit before firing up. The temp in the garage was only a couple of degrees though. I'm not really sure what to do next. I may just leave as is until the warmer weather and then have a look.
 
oelarse

oelarse

Well-known user
I agree with you to wait for warmer weather :)
If you have not measured and verified the drain current yet I will suggest you connect the amp meter in the serial to the negative battery side and observe the value after aprrox. 15 minutes .
If it is way above 30 milliamps , you should look into each fusecircuits like I mentioned above at post #2 .
If you need any schematics , please put a note for it here in the forum and I can upload it
 
F

Firepit

Well-known user
I've finally found the time and weather to take a look at the car. The yellow top I have on the car has a CTEK tender keeping it charged. Disconnect that and try to start the car and again no joy. So definitely need a new battery.

As a precaution I've invested in a battery booster, for aiding start ups, which is excellent. It connects to the battery and enables the Corvette to start instantly.

Took her for a run and everything is great. After that I decided to just see if there was any parasitic drain. I connected my ammeter in series on the negative side and at first got .200MA which settled to 0.08MA

I believe then that this means no drain other than the normal expectations. :)

IMG_7617.JPGIMG_7616.JPGIMG_7615.JPG
 
oelarse

oelarse

Well-known user
In my opinon your current draw indicate a minor drain current . My currentdraw after 12 minute RAP period is .028 (28 mA ) .

This means your battery will last more than double time in my car compared to batterytime in yours .
A 50Ah battery will go empty after 625 hours with 80mA drain current and after 1785 hours with drain current of 28 mA.
If the battery is old and weak the number of hours will be reduced a lot
Here is another tread on currentdraw on the CF forum conforming that a normal current should be in th 20-30mA area .
 
F

Firepit

Well-known user
Good info thanks for that!

I’m going to have another go and leave it for longer next time, as it definitely wasn’t more than 5 minutes before I thought I’d cracked it and gave up. :)

appreciate the guidance.

paul.
 
oelarse

oelarse

Well-known user
Here are some wiring/fuse info on the 01.

You can try to remove fuses to the Radio 5,24 and 28 and see if it make any reductions in drain current .
Also the seat and door modules could cause current drain .( each module two fuses )

Good luck :)


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4262

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4264
 
F

Firepit

Well-known user
Cool, I’ll. order my new battery and then have a go maybe next weekend.

Also, I should have read your earlier responses again, as you were clear about how long to wait 👍. Thanks!
 
F

Firepit

Well-known user
I’ve managed to put the new battery on and do some further testing. The draw at rest was 70ma. I testing every fuse and only found one with any current at all at that was number 5 in the foot well. This protects the radio and cd changer. I did actually replace the changer years ago with a unit to add an audio input like an iPod. So I went into the trunk and disconnected it. The current dropped to 60ma. So retested every fuse, including pulling the ones that don’t have probe points. All of them show zero.

tested voltage with the car running and lights on and it was 14v so the alternator appears good.

The new battery is on and is hooked up to the same ctek tender that has maintained the car for the past six years.

I’m not sure what to do next to try and locate the draw. Or even if I need to.
 
oelarse

oelarse

Well-known user
I guess you have checked both fuseboxes ( in footwell and engine compartment)
If you can live with this current draw , this should not cause any big problem .

I have mounted this CTEK charger with 2.5 m extention cable on my garagewall and permantly mounted CTEK quick connections to the battery.
Easy plug&play to use when I leave the car for more than a week :)

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4353
 
F

Firepit

Well-known user
Apologies for the slow reply. I've had the new battery on for a couple of months now and no further electrical issues have cropped up. The only drain now is extremely minimal and not concerning. I've got the same ctek unit as you so no worries on that score.

I do believe my issues were caused by a rogue low quality red top battery which failed from new even though it was on the ctek tender. Replaced with a yellow top and all fixed.

There is one thing for sure C5 's don't like weak batteries!!!
 
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