I have a 2004 cat 304cr S/N NAD01704. While using machine for awhile the other day it died while digging with no power at all. I checked fuses and starter fuse had blown. I replaced the fuse,started the machine and it blew again after a minute or less of digging. I noticed if I let the machine sit and cool off it would operate for about 10 minutes or so then once warmed up it would blow the fuse and continue to quickly blow fuses until it cooled off again. I have corrosion on positive battery terminal. Took starter off to have it and the solenoid rebuilt thinking there could be an issue with the solenoid causing this issue. All wiring looks good from what I can tell. Not sure where a starter relay may be located on this machine if that could be another part that needs to be looked into. Not sure where to look for sure because it still starts no problem but the issue is definitely occurring consistently with the machine warming up then gets worse once warmed up.Any help would be appreciated. Thanks
Can you post more info like picture of fuse block and schematics if you have them.
The starter fuse is powered off of the main 60 amp relay, 177 orange wire. After it goes through the 30A starter fuse it turns to a 105 red wire that feeds main power to the Keyswitch. I would get a multimeter and as soon as it blows the fuse, test both sides of the fuse terminals for continuity to ground so you can determine which direction you need to focus on.
The pdf you have attached it to blurred to use. If you take a picture of the wiring schematic only and if it is clear to read you might post it. What you are saying does not make much sense as if you use your multi meter after the fuse has blow you would have battery voltage on one side and a short to ground on the key side. The short to ground you measure will be a combination of the fault current (if still there) to ground blowing the fuse and all the other items being powered from the keyswitch which will appear as a short to ground on your meter. You need to go down stream and start separating wires or start second guessing what items powered from that key switch might be the issue. Unless your cranking or using glow plugs there is normally no item that can produce a fault current to blow a 30A fuse so it is more likely a wire in the harness that has rubbed trough or getting pinched and shorting to ground. If all of the down stream items on the keyswitch are fused with smaller fuses then the issue is likely between the 30A fuse and keyswitch.
Thanks 007 I will look into that. So you don’t think there could be an issue with the starter solenoid causing this issue
Probably not If your machine is running and stops it is because of that blow fuse. Starter solenoid is only drawing power from the key switch when cranking. So is something the keyswitch sends power to when running or the lume between the fuse and keyswitch.
I am only going from what you said and not the schematic. You said the 30A fuse feeds the keyswitch correct??
007 Yes when that fuse blows there is zero power at the key switch. Also do you know if there is a starter relay anywhere that could be getting hot and causing this?
The schematic vaguely shows a starter relay on the starter solenoid but why are you so convinced the starter circuit has any thing to do with this. Its it because the fuse is labeled starter? If the starter circuit was the problem the fuse would blow when the keyswitch was turned to the cranking position.
Ok sounds good. You’ve got it from here.
Sorry ahart got mixed up, thought it was tm93 said what that fuse was feeding.
I agree the only thing that has me thinking it could be the starter or solenoid is how it consistently does it after the machine runs for like 10 minutes or so and then blows fuse then continues to blow quicker until it cools off. It just seems like maybe something could be heating up then causing the issue. I feel like if it was a rubbed wire it would do it more randomly or constantly instead of after it warms up it does it then gets worse until cooled off
Circuit isolation when the fuse blows is the only way you will ever find a short to ground in a circuit unless you happen to stumble on it by accident. Unless you have a thermal imaging camera to identify the “warm” component in your circuit that is causing the short, a multimeter is what I use. I have diagnosed many short to ground problems associated with the Keyswitch circuit by isolating parts of the circuit from other parts. If you want to remove all the key powered devices from the circuit, pull all the fuses that are powered off of the 112 wire, that is key power from your Keyswitch.
For example, the other day I had a D6T that blew the Keyswitch fuse while I was installing a blade push arm. After isolating the circuit I was able to find the main power relay was shorted internally due to the fuse panel being 1/3 full of water.
Thanks for the help. I’m no electric expert so sorry if I don’t follow you all the way. So you’re saying a way to isolate the issue is start testing it out while removing certain fuses to things until the problem potentially stops to leads me towards something to look into? Also are you aware of any relays on the machine that I should look into. All I have found so far is a box with a plug plugged into it by the hour meter
Are you able to view the schematic I attached?
Yes I just don’t have a lot of experience with reading schematics
Ok, screenshot any area of the schematic you have questions about and I’ll be more than happy to help you navigate it.
Ok thanks I’ll get back to you when I get to it
Ahart just out of curiosity do you think a badly corroded positive terminal could cause this issue
Corrosion is resistance to current flow so I would say yes, that could draw enough current to blow that fuse. Have you cleaned up the positive terminal and ran it?
Update: Ac compressor had been loose from broken mounting bolt. It just hung loosely and shook while running. I discovered the ac lines had been rubbing the harness for who knows how long, wore through the harness loom and had a couple of bare wires exposed in the harness that were rubbing those ac lines. Fixed harness and reinstalled. Hopefully this fixed it