BobM1980RedCorvette

I had this posted under a different thread concerning accessibility of the fuse block. But here is the issue I'm dealing with.

I did pull the CTSY fuse (someone had put a 10 amp fuse there/I replaced with a 20), and pulled a couple others to look at them (none blown). After looking up, I noted the dome light was on, checked the horn- it honked (button falls off easily), the accessory jack worked and the clock second hand was moving.

I had noted 1 of the 2 horns under the front cowl there ahead of the vacuum canister for the headlights was disconnected. I plugged the connector onto the horn where it had been disconnected...and EVERYTHING that had been working a minute before QUIT (clock, accessory jack, horn, etc.). So I am back to "square 1" and the fuse (20 amp) is NOT blown. Any ideas folks? Is there something that would cause all these items to work, then NOT work, other than the fuse (which seems to be good)

The car is "new to me" as of mid January 2017 with 87k miles on it, and everything worked when I bought it from a specialty car dealer in the s/w MO. area.

henrikse

Did you disconnect the horn and see what happened. It sounds like a ground problem. If they are not wrking get a test light or meter and after ensuring ground follow positive from source. You can get wiring diagrams onsite or google. Willcox has quite a few.

BobM1980RedCorvette

Yes; I did disconnect that 2nd horn that was disconnected prior to my doing work with the fuses, that is, I disconnected it AFTER the courtesy items (dome light, cigarette lighter, etc.) stopped working again.


I will check the dash lights to see if they light or not, later today.

SwampeastMike

The horns themselves are self-grounding (via their connection to the frame) but the relay that operates them is ground-triggered via the single grounding point of the cabin wiring harness. Other things on the CTSY circuit have a similar mixed grounding scheme. While the courtesy lights technically get their ground via the door jamb switches the delay timer that intercepts that ground gets its' operational ground from the same cabin harness ground.

The reason I asked you to ensure that the instrument panel lighting works (when the other things aren't) is because that lighting gets its ground from the same point and will not work properly if there is a simple ground connection problem.

While only active here for a few years, the majority of electrical problems in C3s seem to come from the CTSY circuit. Not only was it increasingly used (and spliced) over the years as it came from the factory but it is also the first place people go to find power when adding accessories.

BobM1980RedCorvette

SwampEastMike: The Dash/speedometer / center console lights (by transmission indicator) all work. I changed fuses another couple of times wondering if there was a loose connection and/or dust that made contact poor, but with no results.....horn, dome light, clock, cigarette jack still 'dead'.

BobM1980RedCorvette

The really WEIRD part about all this is that the system occasionally works...e.g., the other day when I only changed the fuse...and checked a couple others...and then tapping the horn button, it worked, dome light on, etc. 'TILL I connected that horn lead that someone had disconnected. Mike & Anyone Else with ideas...they're all welcome!

SwampeastMike

Intermittent problems are the worst

Do you have a meter or test light? If so check to see if one side of the dome light is hot (+12V). It should be.

henrikse

Without a meter or test light (meter preferred) this will be hard to troubleshoot. First I would take the meter and take a resistance reading on that horn you hooked up to cause this. It should be the same as the working one (disconnested of course for comparison) Either you will find it shorted or not. If shorted when you plugged it in should of blown fuse but could of burnt a ground somewhere. With meter you can check if you have positive voltage at lighter, dome light etc. If you have 12 volts positive check for 12 volt negative at each and then follow wires to find. With meter you can go on 12 volt circuit on fusebox and ground While watching meter wiggle around wires, fuses box to see if you can find intermittent problem

SwampeastMike

All good advice except that the horns get their ground via their attachment bolts--no way to burn those with only 12 volts

I suggested checking for +12V at the dome light because that's the easiest place to find the always on power coming from the CTSY fuse. If no power there then it's not a ground problem.

BobM1980RedCorvette

Yes; I do have a VOM (meter)...actually several of them. So I'll check the dome light power (or lack of it) and other items as you mention, above. I am not sure about getting at the horn / removing it as it's way up under the front cowl area there ahead of the hood/headlight assembly and near that vacuum canister. I don't have car ramps & won't jack it up. I may end up taking it to the local Chevy dealer for JUST this issue. Other things are okay and I don't need a lot of professional service at their rates!

SwampeastMike

Sadly this is the sort of problem that can be extremely time-consuming to find. Mechanics at at Chevrolet dealership may have no experience with cars of your vintage.

BobM1980RedCorvette

Strange; I did take my VOM and tried testing the dome light for current....none. BUT, I thought I'd check the fuse for CTSY items, and as I was putting it BACK in the slot, seeing that it was not blown, the courtesy lights , clock, accessory jack flickered and after jiggling the fuse in the slot a bit, they stayed ON. BUT, the horn won't honk.

I will disconnect BOTH horns and see if I can get to them to test them. Also, the horn RELAY; is that there near the fuseblock under the dask? I researched that on some '78 Corvettes, - 1982 that's where it is. Could THAT also be an issue? But first, the horns...disconnect.

The center button on the steering wheel tends to "fall off", so perhaps that's an issue? Please advise from what you know. THANK YOU. At least I've experienced a bit of progress today.

SwampeastMike

Your experience with the meter at the fuse box makes me believe that you need do nothing more than tighten the fuse contacts with some needle-nosed pliers or two smallish regular screwdrivers. I would do that before taking any other actions.

Regarding the horn relay: If you think the fuse box is a pain to access the horn relay is FAR worse. It just dangles from the wiring harness above and to the right of the fuse box. The snap connectors at both sides of the relay are very effective and given the location almost insanely difficult to release.

All that the horn button does is provide ground to the horn relay coil. It may come loose but it CANNOT cause a problem that results in no power to the CTSY circuit.

henrikse

You could have an intermittent connection on wire at back of courtesy fuse holder as well. Seems you jiggle around it and problem goes away. Know it is hard to look behind but if tighten the fuse block doesn't work?

henrikse

This is from Jim Shea on Corvette forum. He posted this, It is not mine but a great information.

HORN OPERATION DIAGNOSIS - ALL C3 CORVETTES 1969 THROUGH 1982

There are three basic areas that can cause your horns to not operate: 1) the horns themselves;
2) the horn relay/key buzzer; 3) the horn circuit in the steering column and steering wheel parts.

1) Horns - There are two horns on most Corvettes. There is a dark green 14 gage wire connected to them from the horn relay. Disconnect this wire from the horns and connect a 12v source to the horns; they should operate. If they don’t, the horns need to be repaired or replaced.

2) Horn Relay/Key Buzzer – Early Corvettes have the horn relay mounted underhood, on the driver’s inner fender, near the brake master cylinder. Later models have the horn relay mounted inside the car, under the dash on the instrument panel wiring harness coming out of the fuse panel.
Remove the relay from its mounting and identify the #2 and #3 terminals. Connect a jumper from the terminal marked #2 to ground. Slide a probe into the wiring harness connector to make contact if the terminals are the slip-on type. If the horns operate, check the #2 terminal wire and horn switch for defects. If the horns do not operate, leave the #2 terminal connected to ground, and connect a voltmeter from the #3 terminal to ground. If a reading is obtained, check the horn wiring and horns for defects. If no reading is obtained, replace the horn relay/buzzer.


3) Steering Column Wiring - The steering column has a flat (harmonica) wiring connecter that connects it to the vehicle instrument panel electrical harness. The last wire in the steering column connector is a black one. Next to it is a pink wire. The next wire (the third one) is another black wire. There should be continuity from that third black wire up to the spring loaded eyelet plunger sticking up at the horn button upper contact on the steering wheel. If not, the problem is within the steering column itself.

4) Steering Column Continuity - When you press the horn button there should be continuity from the third wire all the way to the lower end of the steering column steering shaft and across the flexible coupling to the flange that mounts to the steering gear input shaft. If not, the problem is somewhere within the steering column, flexible coupling, or steering wheel horn parts themselves