I have a 2008 cat 450E ser# EBL00xxx, was operating fine then hoe and stabilizer controls stopped working. After checking everything else I started pulling fuses, found a blown fuse, replaced it, everything works great for a min then blew the fuse again, rinse and repeat twice more. The fuse location is p20 which says it’s a 20 and controls the fuel pump that sound wrong to me and they had a 25 fuse in it that blew. Anyone have a similar issue or ideas besides filling every wire to see where a short it, or maybe the hydro lock switch? And trying to find a service man or electronic schematic is like trying to get my 2yo down for a nap. Thx
How so.? All you had to do was ask. Check your message inbox. P20 is specified as 20A on the schematic but it is for the Ride Control relay.
Thank you for the schematic my buddy can read that. Will see if he can figure this out. Thank you
Tell him to read all the notes, but especially the table showing the colour codes of the wires, before trying to interpret the schematic.
Ok so we checked the switches now I found that the fuse blows as soon as I turn the key on not start. Could this be a problem w the fuse block, the harness coming out of the block or a short somewhere down the line? Any help is appreciated thx
If you pull the ride control relay out, does the fuse still blow when you turn on the key.? If it does, unplug the 8-pin connector PL-C29 marked CONN 1 below. Does the fuse still blow at key on.?
I will give that a go when I get back to my machine. Thanks again
Pulled K7 relay turned key fuse blown pulled grey 8 pin connector turn key fuse good
OK. Reconnect the grey 8-pin plug. So now you are going to have to start following the 143-PL138 Brown wire on the schematic. That’s the one that carries key switch power through that circuit. Not far to the left of the image above on the schematic it arrives at a splice and goes in about 6 different directions from that point. You’ll have to trace each one of the 143 wires from the splice wherever it goes and unplug whatever is connected to it. Then try the key switch again. If the fuse blows you have a wiring problem somewhere. If it doesn’t blow then start reconnecting components until it does. The last one you connected is where your problem lies.
Super thanks again
If you follow the main highway H1 on the schematic and then H4 it will take you to the splice at Grid I-11 on Page 2.
Ok so printed off the schematic so we can actually read it. Followed it at and the p20 fuse controls three switches and turns out when I have the machine in 4WD that’s what blows the fuse. Long story short backhoe is out of the hole and everything works cept the 4x4 but I can tackle that another day. Thank you so much for all your help.