265 Massey blowing a fuse

[jkk]

Hello, I am new here and this is my first post here. I just replaced the alternator and since then I am having a problem with a fuse that keeps blowing. There is a wire that comes off the starter solenoid (the big stud where the battery hooks to)that has a fuse in the line that goes on up to the amp gauge. When I start the engine the fuse is fine and when I idle the engine up the amp gauge will peg (to the charging side) and the fuse will blow. I have been checking for shorted wires and have had no luck in finding any. Could it be the amp gauge possibly or maybe the alternator? Help!

 

[bakerg]

If you didn't have the problem before and you changed the alternator and the problem started, I would look at the alternator or the connections to it first. Why was the alternator changed in the first place?

 

[jkk]

If you didn't have the problem before and you changed the alternator and the problem started, I would look at the alternator or the connections to it first. Why was the alternator changed in the first place?

The battery would not stay charged and kept going dead. Had the old alt. checked and it checked out bad. I am at a loss, thought it would be as simple as just changing out the alt. and that would be it.

 

[The kid]

The battery would not stay charged and kept going dead. Had the old alt. checked and it checked out bad. I am at a loss, thought it would be as simple as just changing out the alt. and that would be it.

Check your battery with a hydrometer to check your batteries health. Give it a good charge. Is this on a diesel? Basically the heavy red wire from the alternator would either go straight to the battery or the solenoid large wire post. #1 terminal would route thru the oil pressure switch. #2 terminal on a Delco 10SI is not needed for the internal sensing will activate the alternator charging when needed. The #1 terminal is to Ignition thru the OP switch. Be sure to put an inline fuse going from the alt to the solenoid and a #10 size wire. Fuse size can be 20 - 30 amp. FYI the #1 terminal if looking at the two blades is the left terminal. So sake of argument, remove the alternator and take it to your local parts store for a free test. A replacement 10SI will not break the bank.

 

[irvingj]

Does this system have a built-in regulator on the alternator? If not, is it possible that the replacement alternator has a significantly higher output (that the regulator can't handle)? Just a thought, as that happened to me on a '62 Plymouth Valiant quite a few years back. I learned the hard way to ensure the regulator matches the alternator....

 

[Harry in Ky]

There should be no fuse between alternator output terminal(through ammeter) and battery positive. That circuit is battery live, and needs to be capable of 30 to 80 amps, depending on alternator capacity and battery state of charge. The fused circuits should be between battery positive(whether from battery cable or ammeter) and any electrical load, like lights, gauges or anything else requiring fuse protection.

 

[jkk]

I have obtained an IT shop manual (MF-43) that covers the 255, 265, 275 wiring. I am sure (?) that the wiring is correct according to the layout in the manual, but anything is possible at this point. I am going to take the alt. to the shop tomorrow for testing. Maybe that might reveal a problem. I have spent some time unhooking wires trying to eliminate the problem without any results.

Here is the way the wires run:
1) from the bat. stud on the alt. to the left stud on the amp gauge marked L+
2) from that same point on the amp gauge to one side of the key sw.
3) from the other side of the key sw. to the neut. sw.
4) from the other side of the neut. sw. to the solenoid stud marked S
now back to the alt.
5) from the blade term marked #2 on the alt. to the right stud on the amp gauge marked B+
6) from that same stud on the amp gauge to the solenoid stud where the battery cable hooks to(this is where the fuse is that keeps blowing)
7) and from that stud on to the battery+

Thank for the input and your help is greatly appreciated!

 

[jkk]

OK, I took the alt. to the shop this morning to have it tested and it was doing the job it was made to do. The shop guy told me the new alt. put out around 65 amps compared to the old alt. that put out only around 32 amps or so. Here is what he wanted me to do. Tie 2 - 40 amp fuses parallel to each other in the line coming from the battery stud on the solenoid going to the amp gauge. I spliced the 2 -40 amp fuses parallel with each other and heat shrinked the splices. After doing so, I have run the tractor for a while idling and and at higher rpm's and everything functioned as it should. The fuses are holding and there is no heating up of the wires in the circuit. Well there's another one fixed. WOOHOO!
Thanks All!