Charging System Troubleshooting--Blown Ignition Light Fuse?

[ACHiPo]

When I was driving yesterday I noticed the ammeter was at -25A. When I got to where I was going I unplugged the fan and the ammeter jumped to +25A with the engine running without the fan. I plugged the fan back in and drove home. The ammeter read 0 when the fan wasn't on. When the fan turned on the ammeter pegged negative before coming back to -25A.

I spoke to Peter and Doug this morning. Doug pointed me to the troubleshooting instructions on the ERA website. One of the first steps is to confirm that the ignition light is on when in the Accessory position. It wasn't. I checked the wiring diagram and found the fuse. It is blown. I replaced it, tried again, and the light came on briefly then went out. The replacement fuse was blown. The fan circuit fuse is fine.

It seems it doesn't make any sense to further troubleshoot the charging system until I find and fix the short that is causing the ignition light fuse to blow.

Suggestions on where to look?

Thanks.

[ACHiPo]

I jumpered the I&S wires on the VR connector and saw what looked like normal performance on the ammeter. This should indicate that the alternator is ok, so I replaced the regulator, but no joy. I'm wondering if it could be a battery issue? Gonna pull the alternator and battery and have them both tested.

[patrickt]

Originally Posted by ACHiPo

One of the first steps is to confirm that the ignition light is on when in the Accessory position. It wasn't. I checked the wiring diagram and found the fuse. It is blown. I replaced it, tried again, and the light came on briefly then went out. The replacement fuse was blown. The fan circuit fuse is fine.

.

Which number fuse are you replacing?

[ACHiPo]

The third fuse down on the right (facing forward) bank. It is the fuse for the “I” from the voltage regulator.

I bought another alternator today as they weren’t able to test my old one and they’re closed tomorrow, but I really think I have a pretty big short someplace, not an alt problem. The battery checked ok, but that’s just because it was fully charged (not a real test of the battery cells—I still suspect it given the reported issues with cell shorting on gel batteries).

[patrickt]

OK, when I pull the wiring diagram up for your numbered car, I do not see the "I" terminal wire of the VR running to the fuse box. It runs straight to the red ignition light. The "A" terminal of the VR runs to fuse #4, which also runs your flasher.

[ACHiPo]

Patrick,
I’m out at the moment. I’ll see if I can’t get a schematic image and photos showing the fuse and circuit.with

[patrickt]

It does look like the other side of the ignition light eventually gets its 12v+ through the gauges, which is indeed that fuse #3. So, if the fuse is blowing, then there's a short somewhere on that line. What I would do is pull the fuse #3 entirely and set it on the work bench. Then cut the Y/R wire right before the "I" terminal of the voltage regulator and run a clean, fused, wire from the battery positive terminal to the "I" terminal. Then fire up your car and see if it charges properly. If it does, then work your way back on the Fuse #3 line, starting with the fuel gauge, then over to the tach, then back to the wiper switch and search for the short. On the other hand, if doing that blows the fuse on your test line, then the fault is on the voltage regulator side.

[ACHiPo]

Originally Posted by patrickt

It does look like the other side of the ignition light eventually gets its 12v+ through the gauges, which is indeed that fuse #3. So, if the fuse is blowing, then there's a short somewhere on that line. What I would do is pull the fuse #3 entirely and set it on the work bench. Then cut the Y/R wire right before the "I" terminal of the voltage regulator and run a clean, fused, wire from the battery positive terminal to the "I" terminal. Then fire up your car and see if it charges properly. If it does, then work your way back on the Fuse #3 line, starting with the fuel gauge, then over to the tach, then back to the wiper switch and search for the short. On the other hand, if doing that blows the fuse on your test line, then the fault is on the voltage regulator side.

Patrick,
I think you've got the correct fuse number, but here's a picture of the fuse that blew (missing) just in case.

[ACHiPo]

I've got a couple other weird things going on that I didn't think were related, but since that "I" circuit includes gauges, maybe there's a clue.

My fuel gauge has been flaky for a couple weeks. I suspect a bad fuel sender. I was planning to troubleshoot this weekend, but resolving the charging issue took priority.

A few miles after the charging issue first started yesterday, my tach stopped working--it's frozen at 2200 RPM. I suspect this is a result of the blown fuse, which would interrupt voltage to the tach.

Looking at the schematic, if there's a short to ground in the fuel sender, that could explain the blown fuse, although it's not obvious to me the source of enough current to blow a 15A fuse. It also looks like the wiper switch and motor could affect that circuit.

One other observation--after I replaced fuse 3 again I turned the key to the first position and the ignition light went on briefly. At the same time the ammeter jumped to about -15A then went back to 0 as the light went out (and fuse blew). This seems to indicate the ammeter is reading correctly, and that I have a short with enough voltage to drive 15A current, presumably to ground.

[patrickt]

Originally Posted by ACHiPo

My fuel gauge has been flaky for a couple weeks. I suspect a bad fuel sender. I was planning to troubleshoot this weekend, but resolving the charging issue took priority.

Yep, that's a clue. Let's see if we can get lucky -- reach up under the dash to the two green wires going to the spade terminal on the fuel gauge. Pull those two green wires off the spade terminal and don't let them touch anything. Then put a fresh fuse back in fuse #3 and then fire the car up and see if everything, except the fuel gauge, now works properly and charges properly.

[ACHiPo]

Originally Posted by patrickt

Yep, that's a clue. Let's see if we can get lucky -- reach up under the dash to the two green wires going to the spade terminal on the fuel gauge. Pull those two green wires off the spade terminal and don't let them touch anything. Then put a fresh fuse back in fuse #3 and then fire the car up and see if everything, except the fuel gauge, now works properly and charges properly.

Will do that right after coffee (and reinstalling the alternator and voltage regulator ). I'm a hazard to myself and others before caffeine.

Edit: ok one cup down, and my head is clearing. If I pull both green wires from the fuel gauge it eliminates the fuel sender from the circuit, and also the wiper switch and motor. It also seems that if there is a short to ground through the fuel gauge circuit there should be low resistance from the fuel gauge green wires to ground? I think I'll try that test first.

[patrickt]

Here's a pic of the green wires on the back of the fuel gauge that I want you to pull off the spade terminal. This is a pic I took of when I wired in a 10v Smiths regulated voltage supply which I found made the accuracy of my fuel gauge better. That's what I'm holding in my hand. Anyway, the fault is either on that green feed wire that goes from the ignition light, to the fuel gauge, to the tach, and on from there OR the fault is on the other side, which is the voltage regulator. Either way, it should be easy to trace.

[ACHiPo]

Pulled the green wire (no mean feat with a heater installed!) and there was no conduction to ground, but figured I'd try firing up the car anyway. Got the alternator, VR, and battery reinstalled. Turned the key and light on/off (blew another fuse). At this point it has to be the alternator or battery, so off comes the alternator again.

[patrickt]

Before you do that, try my first suggestion of running a clean, fused, 12v+ to the "I" terminal of the voltage regulator, all with the fuse removed and the original wire to the I terminal cut. This effectively bypasses the ignition light. If the system then charges properly, then the short is back on the green wire somewhere upstream of the fuel gauge.

[ACHiPo]

Removed the alternator again. Even though the electrical cut off switch was off I got a little spark when the ratchet touched the overflow tank removing the "Batt" nut. I checked the voltage and it is 0.5V. I ohmed out the orange wire from the fuse block to the alternator and it's fine, but there was also 0.5V between the fuse block (both orange and white wires) and ground. The voltage slowly dissipated so maybe there's a cap someplace?

The new alternator did not fix the issue. At this point I'm back to the battery or a short somewhere in the wiring.

Oh, and as hard as it was to remove the green wire from the fuel gauge? Putting the gauge back in is damn near impossible. I think I will need to pull the steering wheel and dash to get it back together.

The final straw was bumping the visor when pushing the car back into place and having it snap in half.

I'm taking a break for a while and see what other ideas I can come up with from the schematic.

Edit: Patrick I didn't see your note until after the last activity. I will try your clean fuse wire idea when I regain my composure.

[patrickt]

1) If you have a MSD "Noise Filter" capacitor installed, that will indeed hold a small charge after you've disconnected the battery. Always flick on your lights, or hold the horn button down for a second or two, after disconnecting your battery.

2) You do not need to remove the dash. Just remove the half dozen dash screws and you can get your fingers down behind the top of the dash to remove the fuel gauge. Then fish the wire through the hole in the dash, plug it back in, and reinstall the gauge.

3) Remember, fuse #3 runs your wipers, gauges, and heater. If you can get the car to run and charge properly with the "bypass fused wire" running to the I terminal of the VR, with fuse #3 out, then you positively know the short is along one of the two feeds coming off of fuse #3. One of those feeds goes to your heater (that is the light green wire coming off fuse #3), the other is the White/Green wire coming off of fuse #3 that eventually becomes the solid green wire. The short is along one of those two avenues.

[patrickt]

Actually, run a fused 12v+ line to the Green Wire, which you will cut, at the ignition light. That way you can see the ignition light come on, and then go out, when the system starts charging properly. That's a better test.

[ACHiPo]

Originally Posted by patrickt

1) If you have a MSD "Noise Filter" capacitor installed, that will indeed hold a small charge after you've disconnected the battery. Always flick on your lights, or hold the horn button down for a second or two, after disconnecting your battery.

2) You do not need to remove the dash. Just remove the half dozen dash screws and you can get your fingers down behind the top of the dash to remove the fuel gauge. Then fish the wire through the hole in the dash, plug it back in, and reinstall the gauge.

3) Remember, fuse #3 runs your wipers, gauges, and heater. If you can get the car to run and charge properly with the "bypass fused wire" running to the I terminal of the VR, with fuse #3 out, then you positively know the short is along one of the two feeds coming off of fuse #3. One of those feeds goes to your heater (that is the light green wire coming off fuse #3), the other is the White/Green wire coming off of fuse #3 that eventually becomes the solid green wire. The short is along one of those two avenues.

Patrick,
It seems the voltage regulator was eliminated as a possible cause since replacing the electro-mechanical VR with an electronic VR did not fix the issue of fuse 3 blowing.

Given that does it still make sense to run a separate wire?

I tried dropping the dash without pulling the steering wheel and it won't drop low enough to get my hand behind it, so I'm pulling the wheel.

Will check back after I get the fuel gauge put back together.

Evan

[patrickt]

Originally Posted by ACHiPo

Given that does it still make sense to run a separate wire?

Yes, because you want to get the car running and charging normally first, and then search for the short on the line you've eliminated. If running a fresh, clean, fused 12v+ line to the ignition light makes the light come on, and then go out after the car starts charging (because the current through that ignition light excites the VR in to working), then you just move on to finding the short on the eliminated line. That will not be hard to do.

[DanEC]

Evan - you can remove the steering wheel, loosen the brackets holding the steering column to lower it as much as possible, wrap the column to protect the finish, and remove the screws holding the panel and lower it to where the column will support it. Just don't completely unscrew the column bracket - lower it as much as possible. There are so many cables, wires, etc connected to it that it won't go anywhere. Then as Patrick said you can access it from the top.

Wish I could help more on the root issue but Patricks on the case so he will get it figured out - I have confidence in him.

On the broken visor - don't sweat it - gives you a reason to order those from Finish Line with the gold Cobra label like the originals.