1985 vmax main fuse keeps blowing. What should I check first?

[Hemingway506562]

I stopped for gas filled up and turned the key no power at all. I checked on other threads online and I checked one of the main fuses and it was blown. Took the other 30 Amp fuse and plugged it in and that one blew also. What should I check first?

 

[maleko89]

It can be the fuse holder, wiring to it, stator/connections, regulator/connections. Unplug the stator and r/r connections and retest to narrow it down.

 

[sdt354]

Pull all the fuses, put a good 30 amp main in the correct slot, then put each fuse in until it blows. If none blow, disconnect the red line to the regulator and see if that was the culprit.

 

[El Canadiense]

Try narrowing down which system is kicking it out by adding fuses until you have it. Also make sure battery connections/grounds are good and tight.

 

[MaxMidnight]

Pull all the fuses, put a good 30 amp main in the correct slot, then put each fuse in until it blows. If none blow, disconnect the red line to the regulator and see if that was the culprit.

Good advice but remember that if it still blows with all the fuses out the issue could be anywhere between the fuse holder to the live side of the r/r or to the ignition switch (red wire) and back to the secondary fuses (brown wire).
You would be looking for signs of chaffing and around the head stock is a good place to start but it could be anywhere along the loom.

 

[RempageR1]

The blue wires in the headlight unit have 12v directly from the main fuse. So also check those are not making contact with the frame/ground.

 

[02GF74]

Stupid question but did you make any changes or tinker with the bike?

 

[Hemingway506562]

Pull all the fuses, put a good 30 amp main in the correct slot, then put each fuse in until it blows. If none blow, disconnect the red line to the regulator and see if that was the culprit.

I pulled all the fuses then put one 30 Amp fuse in the main fuse box and it immediately blew . What does this mean?

 

[sdt354]

.
IIs the regulator unplugged?

 

[maleko89]

May want to disconnect key switch connector too. That and wires going from that to fuse box and blue wire for running lights are protected by main fuse.

 

[Hemingway506562]

No

 

[Hemingway506562]

The regulator was not unplugged.

 

[CaptainKyle]

The regulator was not unplugged.

Unplug it ! That is the problem a lot of the time with the main fuse.

 

[RempageR1]

I pulled all the fuses then put one 30 Amp fuse in the main fuse box and it immediately blew . What does this mean?

That you only have this left to check:



So indeed, disconnect the regulator and see what happens.

You didn't mention if the fuse only blows with the key turned on or also with the bike turned off. In the latter case, it`s literally just the rectifier left.

 

[Hemingway506562]

That you only have this left to check:

View attachment 80939

So indeed, disconnect the regulator and see what happens.

You didn't mention if the fuse only blows with the key turned on or also with the bike turned off. In the latter case, it`s literally just the rectifier left.

It was the regulator. I ordered a new one from ebay for 15 bucks and installed today. Everything works fine.

 

[Hemingway506562]

Unplug it ! That is the problem a lot of the time with the main fuse.

It was the regulator. I installed new one now everything works.

 

[sdt354]

It was the regulator. I ordered a new one from ebay for 15 bucks and installed today. Everything works fine.

I hope you have better luck with the cheap regulator than I did. They sent me replacements, but getting stuck was no fun.

 

[Hemingway506562]

I hope you have better luck with the cheap regulator than I did. They sent me replacements, but getting stuck was no fun.

I expect to get stuck on a 36 year old bike. I can't believe the oem regulator is 180 dollars.

 

[02GF74]

From what I've read about the cheap Chinese regulators, you may be better off getting a used part.

The regulator/rectifier is pretty standard across a variety of Japanese motorcycles, it's just a matter of finding an equivalent part, mostly based on cc, and number of phases on the generator, 3 for larger cc, 2 for smaller cc.

For example the rectifier failed on my Z1000, having already my made my own rectifier (6 power diodes) note that the 2 separate units. Both were successfully replaced with regulatior/rectifier from a GPZ 750, if memory serves me well, albeit with some wires extended/joined to allow use of the original connectors.

Units that could be used differed by having an extra wire, think that was an additional battery voltage sense.

... but the story is that there should be an equivalent for the Vmax.

....hmmm just looked at the Vmax regulator and it is 3 wire, so doesn't appear to have rectifier built in.... I need to check wiring diagram.

 

[Radioguylogs]

I went to Partzilla, and found the Yamaha part number.

I used the Google search engine to find an NOS OEM part on eBay for $20. It was advertized under "Virago".

Luck was a factor.