TWINRAY

IGN slot, not ACC slot.

I was using this for switched power to the HEI on my ZZ4 powered '69 but it has now stopped providing power and, of course, the car will not start. I was in that area when I put the drivers side kick panel in but put a meter directly on the tab slot in the fuse box (key on position ) but it's dead. I'm stumped��
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doorgunner

I forget the cause of it not having voltage. But my fuse box gradually lost power on several fuses.....I unbolted the entire assembly and found BADLY corroded terminals INSIDE the box itself.

I could have bought new terminals and rebuilt the box, but need a new harness anyway.

TWINRAY

Yikes! But I would think I'd have some power, a few volts at lease?

doorgunner

Some of the terminals had 12v......6v..........0.0volts......

some had intermittent voltage which really will drive you nuts!

'75

Just an fyi, the accessory tap won't have power while the engine is cranking, only with key on or turned to acc. The ideal circuit for the HEI is Ign power, has power while the engine is cranking and in on position.
Not the current problem, but something you might want change.

henrikse

It probably has a fusible link. Check wiring diagram. Usually they won't run battery power without some protection

vettz73

When you had placed the meter on the tab slot in the fuse box, did you still have the HEI wired to the tab? If it was still connected, first try disconnecting the HEI to make sure it's not the cause of the no voltage problem.

TWINRAY

Ok, I returned to this today and thanks to a reply post by DUB on a similar topic https://www.corvetteforum.com/forums...ge-1975-a.html
I've identified the problem. The IGN slot is fused by the fuse to its right. My appeared OK but I replaced it anyway with a new 20 A fuse. Still no power. The I put a meter on the right side of the fuse and got 12+ volts. With the new fuse in place, there was zero volts on the left side of the fuse. I cleaned it up but it still isn't transferring power?

henrikse

New fuse must be shot? Are you blowing fuses when putting them in would indicate a short? Take the fuse out and check with ohmmeter. Are you using correct fuses as there are 2 types (one a fast blo and one a slo blo) some stores sell automotive and electronic which are different.
Any way you can take fuse out and ensure 12 volts steady on one side and the side that is not use an ohmmeter and check between here and ground to see if you have a short? If it reads short you will have to start disconnecting in circuit til you find it.

TWINRAY

Thanks, I'm assuming the new fuse blows when I switch power on.
Problem is that I can't focus with my eyes on the fuse in the fuse box and can't get the fkn fuse out of the fuse box to check it without busting it. What GM moron stuck the fuse box in a location that only a ballerina can access it?
I think it's the radio circuit, I have no radio, I took it out. Maybe a taped up wire lead came undone, I'll look around. Of course, we all know it's impossible to search wires under a C3 dash.

DUB

I do not have my wiring diagrams here at my house but if you believe that it is your radio fuse that is being used to supply power the IGN terminal in your fuse panel.

I believe there is only one wire and it will be a yellow wire that goes over to the radio area and is connected into a three terminal connector that plugged into the factory radio.

One way to check and see if the IGN terminal is grounded...because it is attached to the fuse holder in the fuse panel for that fuse that is blown. remove whatever you have plugged into the IGN terminal in the fuse panel and if the fuse is out. Use your voltmeter and see if when you put the power lead of your voltmeter to a 12 volt source...and the negative lead to THAT terminal...if your voltmeter shows battery voltage....the yellow wire must be grounded some where.

But if you have a wiring diagram...verify that ONLY the yellow wire is the only wire that is coming off that terminal that holds the fuse.
A method I use to get the fuses out without breaking the glass. I have a small jewelers flat blade screwdriver. I go in at the very end of the fuse ...either the 9 o'clock position...or the 3 o'clock position and I slide the tip of the screwdriver down between the very end of the fuse and against the wall of the fuse panel and pry sideways.. IF the correct length of fuse is used...there will always be a gap at either end of the fuse to do this when it is installed. That way...the tool is against the metal portion of the fuse and pry it out. I never go in in the center where it looks like you should pull it because darn near every time I pull a fuse that way the glass breaks due to the excessive tension on the terminal that holds the fuse in place.

DUB

henrikse

Yes crappy place for a fuse box. I am 6'4 and have a tough time as well getting at the fuses. As DUB mentions use a small screwdriver on end of fuse to remove while standing on your head with your feet hanging out the sunroof while listening to Bach! I attached copy of my 73 fusebox. Don't know if its the same but you can see the fuse feeding the ignition tab. Mine is the turn signal and backup lights on fuse . Perhaps you can find your diagram by google.

If it blows as installed which I think it does the positive wire from fuse is dead short to ground somewhere in harness. You did take the wire off the ign tab to ensure it is not grounded?

Gary

henrikse

Here is a 69 that I found. Hard to see fusebox

TWINRAY

Yup, no wire on IGN tab, thanks.

TWINRAY

I tried prying the corner with a small screwdriver without success. The clips really hold down the fuse. I have a plan today to just placr the fuse on the clip without inserting it. Sorta strange it happened all of a sudden? I'll try and trace the wire, thanks.

henrikse

You can use two small jumpers and clip to each side and make it easier to replace fuse temporarily

TWINRAY

Update, my bad it's not the Radio feed but TURN SIGNALS & BACK UP LIGHTS. I was seeing it wrong. I put another fuse in (good thing I have lots of 20A) with the IGN tab empty and the turn signals worked (right side a bit slower than the left?) and one of the 2 back up lights worked - I'll check that ground. The fuse didn't blow. My plan is first to plug the HEI lead to the IGN tab and check for voltage before plugging it into the dz. If voltage, I will then start the car and see if the fuse is ok. Will update.

DUB

'TWINRAY'

You should have power at the IGN terminal as long as that fuse is good. I hope that you get his to work to your liking.

For what this is worth to those who read this and wonder if there is another way.

Before I start this I am quite aware that there are many people who power their HEI off of the IGN terminal in the fuse panel or another area at eh fuse panel or wherever.. If it works for them...fine by me. And I am not saying that if you do not do it the way I do it you are wrong. I am simply explaining why I do it like I do it and if that ruffles peoples feathers....I can not help that because I am dong it like GM did it.

Now I can say I can not do that. Reason being...if that fuse goes out...then the owner of the Corvette will have to have 20 amp...if not higher amp fuses on hand and change them out if it blows. Or I will get phone call and have to hear about it.

I have also seen where the owner of the Corvette pulled current off the clip terminal for the fuse where the power is coming into the fuse panel and not after the fuse itself. I have seen issues with this idea also. Not always...but as we know these fuse terminals can get dirty can corroded and thus cause for an issue on being able to carry the current load.

Now...if a person looks at the wiring diagram on the pre-HEI Corvette and compare it to the wiring diagram for a Corvette with a HEI. The wire coming from the notion switch that goes to teh ignition coil for both designs is basically the same gauge and the only thing GM did was change out the type and size of the wire at the firewall bulkhead connector so the wire going to the HEI I believe is a 12 gauge wire.

So...I remove the bulkhead connector and remove the resistance wire and install anew wire like what GM uses for an HEI and bolt the bulkhead connector back in place. I leave the Resistance wire in the harness so if someone wants to go back to points set-up... the wire is there.

DUB

TWINRAY

This is where I'm at. I think the problem is the tail light / back up light ground (s). The back up light that didn't light had a GOOD bulb. I started to take off the ground wires, that I only put on 2 years ago. One wheeled off! Looks like they were on forever, I don't get it. Didn't have time to finish, will resume Thursday. Update will agsin follow, thanks.

DUB

Will wait for your return.

DUB