Electrical question after lots of reading

[Triumph215]

New to me 1977 Wagoneer has dashboard electrical gremlins. I read a lot of posts here but am not good with electrical so I am still struggling. Initial problem was no dash lights and a weird electrical pulsing, all gauges ok except oil pressure. Oil pressure lead has been cut under the hood so we know the problem there. I removed the dash, cleaned everything and replaced all bulbs, the VR looked ok so I left it in place. Before connecting the battery I checked all the fuses and they were all wrong but one. I know I should have done that first but it ran and I needed to get it home. The dash cluster had a 20 amp fuse in it, I replaced all fuses with the correct fuses. Reconnected everything, still no illumination lights but my seat belt light stays on and now no water temp or gas gauge. Blinkers and High beam lights work both in the dash and outside. Round 2 today, pulled dash again, connected ammeter wires together and taped them up, reconnected the battery and now the courtesy lights all work whereas they did not previously. Why? To me that circuit is alone on the light switch which is brand new. Why would a circuit that is off by itself suddenly work when I disconnect the dashboard?
My plan is to make a ground strap for the dashboard connecting the top screws to the heater ground as I have seen described here. The heater controls all work so I

[Triumph215]

Still need help

Round cluster is hot on F, G, J K & L with the key off.
With the key on only E has power
Pulled headlight switch and no power to J but the fuse held
It seems wrong to me that these 5 posts would have power to them wit h the key off. Am looking now to make some sense of it, any help would be greatly appreciated.

[tgreese]

Hi - First, I will tell you - help with things like electrical is difficult without the vehicle in front of you.

Electrical diagnosis and repair requires a methodical circuit-by-circuit approach. I assume you have a multimeter and know how to use it.

You also need the circuit diagram in front of you. When I was a teenager, I got the diagram for my truck from the local library, and used their copy machine to print out all of it, double-sized. Then I taped all the pieces together, used colored pencils and traced the wires while following them in the truck. This methodical approach may help you.

Replacing the fuses with their correct values is the right thing to do, but it likely will have no effect on circuit performance. Fuses do two things: protect against failing devices in the car, and protect against fire. Typically the situation has to be really dire for the fuse to blow. And generally there is no difference in the performance of a circuit that is fused correctly and one that is not. Put a 20A fuse in a 10A circuit, no change, everything is fine. The 20A will protect against a short (and fire) just as well as the 10A.

Suggest that, if you don't understand why the pins of the round connector are hot, trace back to the source with your multimeter. Look at the wiring diagram, and that will tell you where the wires come out, and their color.

The best thing to do - in my opinion - is to follow the wiring diagram and put everything back to state it had from the factory. I would also suggest that the most common reason for surprising performance is bad grounds. Without a ground, the current in the circuit will seek a new path, and the result may be nonsensical, from our perspective.

Another problem can be corrosion in the connectors. You can pull these apart, spritz liberally with contact cleaner, scrub the wet contacts with a toothbrush, and put back together. Again, a blockage by corrosion in a connector can make the current seek a new (nonsensical) path.

I think you are immediately going in the wrong direction when you make a judgement "seems wrong." Look at the diagram. Measure the voltages. Take one circuit at a time, and confirm that you have the voltages you expect. Slow, deliberate, incremental work. Clean everything, write down your results, and measure.

[rang-a-stang]

That's fantastic advice from Mr. tgreese. With electrical troubleshooting, it is really easy to get sidetracked and thrown around. Then you get frustrated and give up. Focus on the dash lights and get them working. Then fight the other gremlins one by one.

If you do not have a multimeter, get one. It does not need to be expensive. If you don't have that, get one of those lighted circuit testers (a probe with a light in it that checks for voltage).

Your 77 dash is very similiar to my 79 dash. Here is my thread where I fought my gremlins. it has some good info in it.

http://www.ifsja.org/forums/vb/showthread.php?t=182284

Power for your dash lights comes in on pin 5 of the round connector, open that connector and make sure you have voltate there. if you do not, the problem is not your dash cluster. Does your clock or radio light up?

[Triumph215]

Thanks for the replies and the assumption advice, I should know better than that.
I have zero dash lights and have learned there is no voltage to either side of the panel illumination fuse. I started to remove the fuse block but stopped before I got in deeper than I wanted to. I can see behind the fuse block with a mirror, nothing looks melted but the connections look very old and grey. Will do more searching here to be better educated about that before starting.
I unplugged the dashboard, turned the key on and the Gauges fuse did not blow. Tomorrow I will start it to see if the electrical pulsing is gone, this is really what I want because it creeps me out that the ignition system is absorbing this fluctuation. Will remove the dash pod again and make a 3 amp fuse pigtail so I can check each post individually. I plan to just go around the circle and see what happens. I made a nice ground strap to the heater ground based on a post here as I have about 3 ohms of resistance between the bulb power side and the ground side. I don

[tgreese]

Note that the dash cluster requires a ground. Disconnected from the dash steel, the cluster is floating. The gauges' voltage regulator cycles on and off to "regulate" voltage. Without a ground, it will be on all the time, sending full battery voltage to the gauges constantly. The gauges cannot stand much of this ... they will overheat and die. Be careful testing the cluster.

Don't use the apostrophe on your phone or wherever. The forum software seems to interpret that character as "end of message." Single quote on the PC keyboard is ok.

[nograin]

tgreese's advice is really sound.

I'll add this.
These automotive electrical systems were not laid out like a house or building with all power going to a fuse box for distribution.

First, there are two sources of power, the battery and the alternator.
The supply wires from both of them are joined to the main circuits at a welded splice.
The main circuits are:

1. Feed to the Fuse box's hot buss.
2. Feed to the Headlight switch's B1 terminal for the headlights.
3. Feed to the Key switch.


Everything up to the switches is always hot as long as the battery is connected.

Circuits in the fuse box that only get power when the key is in Run or Accessory position are fed from the 'Accessory' feed.



Dash lights get power from the fuse box like this.
The headlight switch has a second feed terminal marked B2.
It gets power from a fuse that is always hot.
B2 power supplies the outside marker lights and the rheostat in the headlight switch's on/off knob. The rheostat output then goes back to a small fuse, then to the dash lights.


Courtesy Lights are same circuit as dome light(s). Any one ground should turn them on.


I never like taking the ammeter out of the equation when there is no need. It leaves you blind.

[Triumph215]

I still have a pulsating electrical system.
I bypassed the ammeter and unplugged the round connector from the PCB. I was hoping this would take the dashboard circuitry/CVR out of the equation. Am I correct in this?
I started the truck but sadly my lights still pulse with the same even regularity.

Over the next few days I plan to change over to the solid state 5v regulator and test all my gauges and the PCB with a motorcycle battery/3 amp fuse and 5v regulator. I was sure the CVR was where my pulsing would lie because I cannot think of anything else that pulses so regularly. I have a new Motorcraft alternator, NAPA voltage regulator, solenoid and starter (stock replacements, all were worn out and tired except the VR) and it still does the same exact pulsing as when I bought it three weeks ago.
Over the next few days I hoped to be getting rid of the Prestolite and moving to a Dualspark Electronic ignition but I would really like to find this pulsing thing before plumbing it into my new ignition system.
Any ideas for me?
I dont know where to look anymore, I have addressed everything I know to address and am out of ideas. How do I find the source of the pulsating?

[Cliff]

Hey Triumph - with a TR4 you should know all about electrical Gremlins!

Great advice from all, good luck with it. Had similar problems myself with my 77 Cherokee. The only thing I would add is clean all contacts, even if they look clean and use dielectric grease (sparingly).

[rang-a-stang]

Do any of the other items in your truck pulse? Headlights? radio lights? interior lights? If not, then the source is in your dash. That CVR can be tricky to isolate. You have to make sure you unhook both sides of it. I did that with shrink wrap on a post inside my temp gauge.

[tgreese]

What pulses? The gauge readings? The headlights?

If the truck runs, I would leave the ignition alone for now. First make everything work like it's supposed to, then start modifying.

If the dash lights pulse in time with the CVR, you can carefully remove the noise filter from the back of the cluster. Careful not to break the pins. This will shut off the CVR and your fuel, temp and oil gauges will go dead. Then look if the pulsing is gone or not.

[Triumph215]

Everything pulses, right back to the battery. Got my fuel gauge out just now and both windings are pretty burned, 5 volts isn't getting through at all. Truck still pulsing.
And LOL you would think the TR would cure me of electrical ignorance but it still vexes me.

Continuing on dashboard CRV fix, agree not to muck up a running truck.

[rang-a-stang]

If your truck is not running, and you turn on the headlights, do they pulse? If not, what is the voltage across your battery? Then start it and read your voltage across your battery. Is it battery voltage then up, then back to battery voltage or is it battery voltage, then below battery voltage, then back up to battery voltage?

[babywag]

If it's a 77 with motorola alternator and external regulator I'd start with making sure all wiring is sound and replace regulator.

Old Fords it was fairly common for "pulsating" lights.

[tgreese]

'77 is Motorcraft, according to my books. And a mechanical (!) regulator. Probably more reliable than Motorola, but still not in the same league as the unitized Delcos.

The Motorolas have rectifier diodes that are very unreliable. This was even a problem in the day - the line techs (mechanics) would take apart the alternators and solder-in new individual diodes, as a warranty repair. If one diode is open, that makes a changing charging field (3-phase with missing cycles), which could look like pulses I suppose.