Electrical gremlins with climate control, aerial & dash

[jklumpp]

A strange thing happened when I drove my corvette today.....
As a background, I have a parasitic power drain problem that I have not got to the bottom of. If my car is not driven for a few days, the battery will go completely dead (only a new battery), so I generally keep it on a charger.
I've just got back from a weeks holiday, so the car has been sitting for some time with the battery on charge.
When I drove it today, all was OK - until Parked it and noticed the first issue - the electric aerial did not go down.... I turned the ignition on & off a few times, but still no good.
Then when I left to drive home I noticed 'SYS' appear on the dash, where the range/fuel economy is usually displayed... it eventually changed to the range, but would intermittently flash 'SYS' as I drove
Then the third thing I noticed was that I had no climate control! The orange background light was on, but there was nothing on the display, and no lights on the AUTO or OFF buttons, and I could not raise any codes by pressing the fan up/down buttons....

When i got home I disconnected the battery for 5 minutes, and then reconnected hoping it just needed a reset, but no joy.... all problems still there.
I also checked the fuses, and they all appear OK.

Any suggestions?

[gtc]

Any suggestions?

Not sure about C4s, but a couple of the usual suspects with C3s are radio memory and alarm systems. I have a battery disconnect switch on mine so that the charger has a chance to do its job.

Like this one: https://images-na.ssl-images-amazon.com/images/I/71y1Stz%2Bf6L._SL1500_.jpg

[Vettech]

Yes on C4's there is a normal draw down on the battery, but it is very small, and even after a week or two would only draw off the batteries surface charge.

Unfortunately a lot of electronics are actually "on" all the time, in the so called standby mode, c/w soft touch switches.

At home on the mains, whats a few extra watts on the bill, day in, day out.

The problem can be exacerbated by the circuits used, a broken earth connection, can cause all manner of illogical wierdo stuff.

I have a Rhino alarm on my 87, left on it flattens the battery, so its only switched into circuit when  Miss Muffit is on board.
She likes the facility of the keyless remote access to BOTH doors. Besides the OEM alarm is quiet satisfactory.

You need a multimetre - one that reads DC current, cct diagram, time , patience, isolate one cct at a time. Probably start with the ones playing up.

But remember to disengage the OEM alarm, to avoid false leads.

Not sure on a 91 but modern electronics use microprocessor chips to retain settings and memories, today "Super Capacitors" can hold a charge for months, this holds info in memory. Electrolytic Capacitors have a habit with heat and time to either dry out and go open circuit, or boil their guts out and/or explode, the mess cooks & shorts or eats away other components.

You need to get an "Electrical diagnosis service manual Supplement". This is a GM book, breaks the ccts down, is very explanitory, good value.

OR - a good serviceman. (This option also requires a fat wallet)

[Vettech]

Oh -  on the 90 there is an issue with the electronic climate control, it comes on and displays but will not respond to buttons pressed.
Today it may allow a button or two, but will he different tomorrow - I'm not sure about the display, its well documented c/w youtubes.

Yours maybe a further step in this fault - which by the way is dirty switches in the panel. Easy fix, but follow youtubes on removal to avoid busting plastic clips etc  that secure the console.

From memory, the ariel has a -Ve supply, ummm, cant remember esp after yesterdays lightning strike ~30metres away blew up the gas mains, at least now I know all the little hairs on mybody work, they went beserk when it hit.... I'll check my 87 book - I doubt GM would have changed it.....

[Vettech]

The antenna has five wires.
1. Coax lead to radio.
1. Heavy braid to earth - this is essential for good reception.
1. Gray or UP wire.
1. White or DOWN wire.
1. Dark Green - power return wire.

These connect back to the Antenna relay - kinda wrapped up and hidden up under the rear, close to the rear glass lock (Coupe).

The relay has six wires - the White, dark green and gray as above. Then..
1. Black to earth.
1. Orange to the Ctsy/clock fuse -12ve. This feed is hot at all times and drives the ariel motor
1. Pink is the -12ve from the radios "On - Off" switch, and only energises the relay, this is suplied by the Radio Fuse.

If radio comes on then fuse ok, if ariel does not, then check CTSY/CLOCK Fuse.
The CTSY/CLOCK Fuse, supplies a trillion different systems - Oh! Including " Heater AC Control Assembly" (C68 Electronic)

Hope this is helpfull. I would tend not to try and remove the ariel from bad past experience.
With all the different problems, I think you have either HR earths and/or wires shorting.

Regards 

[jklumpp]

You're a legend Vettech!

I've just found the CTSY fuse was blown (must have missed that one first time around!), however when I replace the fuse it blows immediately, so obviously a short somewhere.....
I don't have a full wiring diagram, but from what I can see all the courtesy lights (Corvettes have a LOT of them!), the aerial & I'm you have said the climate control display all go through this fuse....
​​​​​​​The search continues.....

[Vettech]

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