More electrical gremlins (1 Viewer)

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Yes , fuse block is not grounded. I keep forgetting. The transfer indicator switch is also on that circuit. Number 31 is the indicator.

Transfer.PNG
 
I had the gauge cluster out so I pulled out my fsm and looked up the section for testing the gauges....the resistance between the two studs ( with the Barrell connector plugged in and the key on )for the oil gauge was out of limits, book calls for 44 Ohm. The gauge sweeps but has been reading high the last couple times I've started up the truck. I checked the oil level and it's not overfull or anything
 
Since the heater fuse supplies the meter cluster, have you noticed any issues with the meters? If a sender or associated wiring was grounding, it would peg a meter and blow the fuse.

I did notice yesterday during my drive that the oil pressure guage was reading higher than it should. but it wasn't pegged all the way over. I got a copy of a 75 FSM and I did two of the three tests for the oil pressure gauge

1. With Key On, Engine Off and the Barrel connector plugged in I pulled the wire from the pressure sender and touched it to my LED test light (it says use a 3.4w bulb and I didnt have any) The test light lit up and the gauge needle moved up., I only did this for a few seconds. According to the FSM this is how it's supposed to work.

2. Since the cluster was out, I checked the resistance between the posts for the oil pressure gauge and it read anywhere from 45-80Ohm and would frequently go to OL. I tried this with key on and key offf.

So one test says it's good, while the other says too much resistance. I need to test the sender as well

At this point, if mine is actually bad, does it make any sense to try and find new Toyota gauges and try and repair mine? It looks like most if not all of it is NLA.
 
with a 3.4 W bulb you would be using 23 to 64 Ohms of resistance depending on the battery voltage. With the LED you wouldn't be anywhere near that. So I would not rely on your test as being valid.
 
Another long shot. A good fuse has NO voltage drop across it when NOT blown. (very small). As soon as it blows, 12 volts will be seen across it, as read by a meter. So, some clips on both sides of fuse will read 0 v. When you drive, observe when it blows and perhaps get a clue. Maybe it is nothing , maybe it is something.
 
Still slowly testing things out and making small improvements. The parking brake switch was completely shot and full of rust, so I have a new one in there and now the dash light works properly. I also ordered and received the FSM for my year and that has helped a bit.

Today, I disconnected the gauge cluster and went for a good drive, and no blown fuse at all. Beginning to wonder if the VR in either the fuel or oil gauge (cant remember right now which one has it) is acting up.
 
Changed a few more items out and happy to report no blown fuses on the test drive, even with the cluster plugged in. In the end, the closest thing I found to a smoking gun was the parking brake switch. On the last instance of it blowing the fuse I touched that switch and it was hot enough to burn my hand. I took it apart and it was full of rust powder. I replaced it and the warning light bulb in the dash so that all correctly works again.

Also cleaned the guage cluster pcb and replaced all of the screws and nuts for the guages since they were all really rusty. Last item I replaced was the ignition switch. It had some slop in it, but wasn't terrible.
 

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