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Discussion Starter · #1 ·
Has Anyone ever replaced the diodes on a JD 2305?
Is there 6 or 7 diodes?
Is 4 of them blue and 3 black?
I'm having a starting problem and since the tractor is 15 almost 16 yrs. old, I thought I'd just replace all of them.
Had the same problem last year, dealer replaced the fuel solenoid shut off and a diode.
Worked fine up until now so, I thought I'd just replace them all.
 

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Has Anyone ever replaced the diodes on a JD 2305?
Is there 6 or 7 diodes?
Is 4 of them blue and 3 black?
I'm having a starting problem and since the tractor is 15 almost 16 yrs. old, I thought I'd just replace all of them.
Had the same problem last year, dealer replaced the fuel solenoid shut off and a diode.
Worked fine up until now so, I thought I'd just replace them all.
My 2305 developed the same starting problem a couple years back just before I traded it in (I think it might have been mad at me). After trying a lot of different things, I finally traced the problem down to being the infamous V4 diode problem. Replacing that diode solved the starting problem for me.

I believe there are 7 diodes in all, but of 2 different types (this is from memory). These are actually double diodes, thus have 3 connectors. My emergency flashers had sometimes not worked, and it turns out that was due to a diode problem as well (of the same type of diode). As I was diagnosing the problem, I removed and tested all 3 of the diodes of the same type as the V4, and found that one was dead (thus the starting problem), one was very weak (thus the flasher problem), and one was sound.

Just finding the V4 diode was difficult because it was way down deep and covered in lots of tape, but if your dealer has already replaced it once, presumably it won’t be too hard to find.

There are several good threads on this topic here on GTT, and also a link to a video of a guy replacing the V4 diode that I found very helpful.

Regarding replacement of the other 4 diodes of the other type, my suggestion would be to avoid fixing something that isn’t broken.
 

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Discussion Starter · #3 ·
Update,
I called John Deere today and ordered V4 diodes which is what I believe I need.
Here's the problem.
The parts guy at J.D. says it requires 4 diodes.
Now I have a downloaded service manual for my 2305. I looked at the schematic and could only find 3 V4 diodes.
So, those of you that are wise in these ways, is there 3 or 4 diodes and if there are 4, where in blue blazes is the 4th one?
 

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That is odd. JD Parts shows there are 4 but it only illustrates 3 of them.

785925
 
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WHEW!!! Parts diagram is REALLY screwed up! Diagram shows 3 #6 diodes, parts list says 4 required. These connect to #7, parts list says 1 required. Down lower, diagram shows 3 #36 diodes, parts list says 2 required...plus another 3 #7 connectors. Further down ANOTHER #7 connector.

Hopefully, a Tech Manual will have a schematic and have correct quantities shown. Bob
 
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The three you have circled have a connector (item #7) associated with them. There is a fourth #7. I wonder if that is where the fourth should be and just not shown for some reason?
Actually, I see (7) #7 connectors.
 

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WHEW!!! Parts diagram is REALLY screwed up! Diagram shows 3 #6 diodes, parts list says 4 required. These connect to #7, parts list says 1 required. Down lower, diagram shows 3 #36 diodes, parts list says 2 required...plus another 3 #7 connectors. Further down ANOTHER #7 connector.

Hopefully, a Tech Manual will have a schematic and have correct quantities shown. Bob
I see that. The #36 diodes are a different part number. All these simple diodes sure can wreak havoc with these tractors.
 

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When I replaced the V4 diode on my 2305 it was part # LVU804171 which cost $21.50 at the time. There are 3 diodes of this type on the tractor.
 

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Hmmm, and yet another discrepancy in the parts list!!! LVU804171 is listed as a V2 diode in the parts list! Bob
 

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I don’t think it is a discrepancy so much as a labeling or cross-referencing issue. From memory, the 7 diodes on the 2305 are labeled V1 through V7 on an electrical parts diagram somewhere (that I remember seeing but don’t have at the moment). The ”V4” diode is part # LVU804171, as are 2 others, probably the V2 diode as you found, and I vaguely recall that the 3rd one might be labeled V7 but I’m not totally sure of that.

Of the diodes of this type, one is involved with the fuel shutoff solenoid (and this failure of or problems with that diode cause intermittent or hard starting failures); another of these diodes is involved with the emergency flashers and turn signals; and I don’t recall what the 3rd one does.

One other note: I found that these diodes can “degrade” somehow, leaving them in a partially functional state. This will cause intermittent failures of the starting system, flashers, or the other thing. Most voltmeters have a diode testing function you can use to diagnose the health of each diode (once removed from their socket, which I found to be really difficult to do).

Also keep in mind that these are double diodes, i.e. each is composed of 2 diodes. I found that one of my double diodes had one good half and one degraded half, which further added to the odd behavior of my tractor.
 

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Thanks Stan for reposting. I found that video very useful when I had my V4 problem, so I’ll imagine that others will too.
 

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Discussion Starter · #14 ·
I watched that video, only shows 3 diodes.
When I go to pick up the diodes, I'm going to the service department and ask one of the mechanics if there is a 4th diode.
Otherwise, I'm only buying 3.
Thanks for all your help.
 

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There are only 3 diodes of this type (LVU804171) on the 2305. These diodes are notorious for failing. There are many threads here on GTT about this.

There are 4 other diodes of a different type. I have never heard about these causing any problems.
 
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