1975 FJ40 Instrument Panel Not Working

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How can I test if the LR going to the speedo has power? Or, if I have a switch on (blower motor) how can I test that it is getting power.
Interestingly, I can get the lights to work with the key in the off position (note that the headlights don’t work and brake lights don’t work...could be the bulbs for the headlights, I have new bulbs in the brake lights...how could I test those to see if power is getting there.). Basically nothing on the panel works...hazard lights, fan/blower or wipers (no clue about cig lighter). No reverse lights. Not sure anything is getting power.
 
"How can I test if the LR going to the speedo has power? " With the battery connected and the key in the run position, using the multimeter set to DC Volts put one probe into the correct terminal in the PCB Connector that goes to the instrument cluster and the other probe to ground. You should read battery voltage.

Which lights do you get to work with the key in the off position?

Are all of the fuses still good?
 
No DC volts at all coming from the LR wire into the PCB Connector. In fact, none of the ports had any DC Volts...if I saw anything, it was .02 volts that flickered on, then back to 0.00. The engine was not running, just the key in the on position.

All running lights but no headlights work with the key in the off position. Brake lights did not work either.

All of the fuses are still good...thankfully.
 
OK Let's work on the cluster first. The LR wire is the power to the cluster. Without 12VDC on the LR wire there won't be anything happening in the cluster. Also the LR wire feeds a couple of other circuits so we may solve some other problems down the line. Those circuits are the Back-up Lights, Blower Motor and Heater Switch and of course, the Instrument Cluster.

According to the 79 wiring diagram the LR wire is fed from the ignition switch to the switched side of the fuse panel. We know that there is power there because it also feeds the Engine fuse circuit, which we just fixed. We should now be working on the fuse labeled HEATER. See if there is power at the the fuse first. If not check the fuse block and see where the break is. Then trace the voltage and find where it stops. Correct that and go to the next point until there is power to the Instrument cluster and all of the other circuits the LR feeds..
 
Sort of did what you said. Didn’t have a lot of time so I tested DC volts to the fuse panel. The switched side (I think...green connector) all had over 13 volts (engine running to charge the battery). The other side of the fuse panel had 0 volts. I think that is correct?

The engine running Ohm’d the barrel connector. They all started out around 7ish then dropped to somewhere in the 1st etc. BUT the LR wire didn’t have any ohms...didn’t register. It didn’t bounce and settle close to 1...it just didn’t register. So I guess that means that wire isn’t getting power wo I’ll have to trace it tomorrow.
 
Groucho263 said:
Sort of did what you said. Didn’t have a lot of time so I tested DC volts to the fuse panel. The switched side (I think...green connector) all had over 13 volts (engine running to charge the battery). The other side of the fuse panel had 0 volts. I think that is correct?

The engine running Ohm’d the barrel connector. They all started out around 7ish then dropped to somewhere in the 1st etc. BUT the LR wire didn’t have any ohms...didn’t register. It didn’t bounce and settle close to 1...it just didn’t register. So I guess that means that wire isn’t getting power wo I’ll have to trace it tomorrow.
Click to expand...


key on

both sides of blue wire red stripe have B+

you have a bad glass tube fuse

swap it out for good measure anyway

bet that might be a fix ...
 
It’s a brand new fuse...and it’s good. It’s got good power at the fuse panel, right?
 
your ignition switch new or old ?

oem or aftermarket ?

the 2 fuse box green and black connectors melted or ok ?

green 4 pin connector from key switch to main harness melts alot from age and time too


or

worse ,,,,,,,,,



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Ignition switch is the one that was in the truck when I got it. The on switch doesn’t seem to work (the first click of the key). No other burnt wires or connectors. I fixed all of those...I think.
 
With the ignition switch in the on position there should be voltage to the switched and unswitched positions of the fuse panel. You are correct, if there is no voltage on the LR at the instrument cluster connector then you need to trace that and find the break. Let me know what you find. I would start at the ignition switch then the fuse panel then the wiring harness.
 
When you say there should be voltage to the switched and unswitched position on the fuse panel...can you clarify? I have volts on the green side but not the other side. The LR wire into the fuse panel doesn’t have power. I traced the LR wire as far as I could into the wire bundle and no breaks...but also no volts or ohms for any LR wire. I feel like we are missing something...nothing electrical seems to work yet everything seems to be hooked up correctly. Ohm’d the barrel connector again. All the wires except LR started at 14 is then dropped to 0. LR had nothing.

The BW wire on the ignition had 0 volts when the engine wa running. This is a bigger gauge wire that goes to the starter. The other 3 wires had good volts.
 
The fuse panel is fed from two sources of power, One source is always on providing 12VDC, these are the unswitched positions of the fuse panel. The second source comes from the ignition switch and is only providing power when the key is in the on position, these are the switched positions of the fuse panel. If you have power to one side of the fuse panel you should have it on the other side, it just goes thru the fuse. There isn't any switches or other devices st the fuse panel.

Can you send me a pic of what the green side is?

I believe the BW wire will only have voltage when the ignition switch is in the start position. This goes to the starter solenoid.

Tell me what color wires you have at the ignition switch connector.

If you have a LR at the ignition switch it should have 12VDC when the ignition switch is in the on position. If it does then check that the LR has the same voltage at the fuse panel. This should feed 12VDC to the switched positions of the fuse panel. Then check all of the fuses that the LR from the ignition switch provides 12VDC to, there should be voltage on the output side as well, if not trouble shoot the fuses and the panel. The panels are known to fail as well. Once the fuse panel and the fuses check good continue down the LR wire, there has to be a disconnect some where. When you come to a connector inspect it thoroughly and clean it and make sure the contacts are clean and shiny. Call me if you need help.
 
Here are a couple of pictures (ignition switch included). In the pictures, the top of the picture is the top of the fuse panel. The black connector and white connector have the following volts with the ignition switch in the second detent which I think is ACC? The first detent is On and the third detent is Start?
Fuse 1 (from top) - GR - 11ish volts
Fuse 2 bigger GR - 0 volts
Fuse 3 RB - 11ish volts
Fuse 4 LR - 0 volts
Fuse 5 bigger LR - 0 volts
Fuse 6 GR - 11ish volts
Fuse 7 BY - 11ish volts
Fuse 8 R - 0 volts.

On the right side of the fuse panel (green side) all terminals have 11ish volts. All fuses are good.

With the key in the first detent (On)...the left side (black and white connector side):
Fuse 1 - 11ish volts
Fuse 2 - 0 volts
Fuse 3 11ish volts
All the rest are 0 volts

On the green side:
All have 11ish volts except the 2 bigger BY ...fuse 5 and 6
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FANTASTIC!!!! This is excellent information.

First, the ignition switch positions are ACC then ON or RUN then START.

The Green terminal is the supply side of the fuse panel. All of the power comes from this connector and goes to the fuse panel. It is great that you have voltage on all of the wires with the ignition switch in the ON position.

There seems to be a problem at the fuse panel as there are several fuses, 2, 4, 5, and 8 with 0 volts with the ignition switch in the ON position. Those need to be corrected first and all should have voltage before proceeding. Great work!!
 
Hi...this is good because patience is wearing thin! How do I get volts to those fuses? Is that a new fuse panel?
 
I would take the panel apart and see if anything is broken/missing. I think this is where most of your electrical gremlins are living. Post pics after you get it apart. The panel looks to be in good shape on the outside. Don't forget to disconnect the battery cables and you may want to put a charger on.
 
The PO had this kit (see picture) that looked like he ordered at some point. I'm wondering if I just try to install this one:

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That's all the further it comes apart. Clean the terminals and the fuse holders nice and shiny. Then put the fuses in and make sure there are 0 ohms, or close to 0 from supply side to load side terminals. Clean the contacts in the connectors as best you can and reassemble and do another ohm check between the connector terminals. If that all checks out put it back in and attach the battery and see what works.
 
I usually use a brass .223 bore or breach brush to clean the fuse contacts with and some salt and vinegar followed by a DI water rinse. A tooth brush may work as well. The flat terminals that the connectors go onto is easily done with a toothbrush. The terminals inside the connectors are a PITA.
 
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