Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

[outboardnut]

The little fuse, 5/8 inch, 20 amp on the v-4's all through the 70's.

I was think the voltage was up around 128 or so. I ordered a package of Buss fuses, the only ones I could find in 20 amps and the short length, BP/AGA-20 (whatever that means). Turned out they are only 32 volt, 20 amp.

Ok to sub?

 

[ezeke]

Re: Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

AGA-20 is correct.

 

[Texasmark]

Re: Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

The AGA or similar lettering refers to the dimensions of the fuse. Sometimes SB is added to signify slow blow, but usually you can look at the fusing element and if it is spring loaded, it is a slow blow.....question is, what is the blow rate?

The voltage rating is the voltage that the blown (slowly blown with a narrow gap) fuse will hold off once blown. For your system the 32v will do fine.

Obviously the amperage is the current at which the fuse opens the circuit, but that is subject to interpretation and all that has to do with heat, the rate of application thereof and the amount of heat sinking available.

Then there are slow blow, fast blow, extremely slow, extremely fast and all the other stuff to confuse you. Circuit breakers are worse yet as there may be half a dozen thermal curves for a given design.

So now that you are thoroughly confused, just get one that fits and has a single straight wire running the length (includes a flat tab with the center width reduced on 10A and larger), or a single wire that is sawtoothed, with the amperage number you want and you should be good to go.

On the newer ones (forget the name....senior moment), the ones with the colored plastic cover you have no choice. You get regular blow and that's it.

HTH

Mark

(I forgot more than I ever learned and it didn't take a lot of effort)

 

[outboardnut]

Re: Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

Ezeke and Mark, thanks for the answer.

Mark, I appreciate you taking the time to go on about the different types of fuses. Yes, you thoroughly corn-fused me for a moment. However you wrote enough to peak my curiosity!

I had taken notice of fuses filaments different ways before, and wondered, but never researched or looked into the why's until after reading your post. Hadn't heard of slow blow, etc....wound up googling it and was able to grasp the concepts. Interesting stuff, makes perfect sense to have different flavors of fuses, pretty crafty.
In the past whenever I had trouble with a fused circuit blowing constant I would sometimes just go up a fuse. Now that I am edumacated a little I will reach for a slow blow fuse first to see if it's just a spike causing it.

Thanks!

 

[Texasmark]

Re: Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

In the past whenever I had trouble with a fused circuit blowing constant I would sometimes just go up a fuse. Now that I am edumacated a little I will reach for a slow blow fuse first to see if it's just a spike causing it.

Thanks!

Not the right answer. As I said, the time to blow is very subjective so the circuit designer has to come up with an "average overload". The purpose of the fuse is to prevent damage to the equipment (including wiring) it is designed to protect. All this has to do with temperature in the equipment which is affected by current and environment.

As you picked-up-on, time delay fuses are designed to sustain an instantaneous surge, yet open the circuit for a continuous overload above the designed value. Designers factor in the surge curves of equipment which has a high starting current, or equipment that may experience a momentary fault from time to time when making the fusing decision.

Your idea to use a time delay fuse, rather than going up a size (in current) is a wise decision. Apparently you have been lucky in the past and your upsized fuses fell into the window known as "average overload". Course if your overcurrent mechanism is a 10x overload, a slight change in fusing value would have little consequence. Where you would notice a problem most would be a mild over current that persisted. However, there are some applications that require an immediate break....Audio amplifier circuits come to mind. They use like a 1/4 ampere fuse and want it to open with the slightest problem to protect the output drive components.....like if someone shorted out the speaker terminals.

Littlefuse is an OEM (that I can remember) and has about everything you could ask for in the way of circuit interrupters. Their components are readily available from numerous distributors. Their site should be a wealth of information for you as you may have already observed, by your comment.

Mark

 

[ezeke]

Re: Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

The OEM fuse is not a slow blow fuse. It's a Buss (Bussman) BP AGA-20 and that is a fast fuse.

The fuse is the correct one to protect the harness wiring so if you have any doubt, buy the OEM part from your BRP dealer - part # 0510884.

 

[jay_merrill]

Re: Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

One of the things that makes particpating in these forums a very positive experience, is the depth of knowledge present in their contributors. This is a very interesting discussion and I have learned a couple of things by reading it.

That said and while "workarounds" are sometimes the only option, when trying to keep an older motor going, my general view of things is that its better to use an OEM or equivalent part, if its available. I can think of a few exceptions to that philosophy, but in this case, why not make life simple? The fuse is readily available and if you install one, you won't have to worry about the situation.



???

 

[tashasdaddy]

Re: Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

i have ruined several items with slow blow fuses. it becomes a smoke test.

 

[Home Cookin']

Re: Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

i have blown a box of those fuses this fall and winter trying to chase a wiring ghost. I was wondering at one time if maybe my automotive store fuses were too "light" but I found an OEM my dad bought new with the motor in 1988. It blew.

Now at the age of the motor, like at my age, a blow is a blow, slow or no! And far more often in my engine....

PS knock wood I think we found it. Mechanic loaned me a control box for the ignition and tilt and bypassed mine, and no blows last weekend.

 

[Texasmark]

Re: Are 32 volt 20 amp fuses OK for v-4 johnnyrudes 70's?

Beins this is moving right along, I bought a new farm tractor a couple of years ago. It had a 30A modern day fuse (plastic top, parallel blades, fast blow....whatever the AGA or whatever number it is) to run the AC, blower, cig lighter (I don't use), and an aftermarket, but factory installed, air seat....like 18 wheelers use. The EE on the job must have been on coffee break when this wiring drawing went through for review. The seat had it's own air pump so it needed 12v to run that.

The wiring to the seat came from the side of the cab where the cig lighter was (as mentioned, 30 A fused) and the wiring (all of 16 AWG) went across the floor and up and under the seat. The seat shock absorbing mechanism was the air bladder and also a scissor system. In short, the scissor system (moving up and down with me) caused the 12v terminal to pull off the pressurization switch so it was just lying on the metal floor of the seat and started shorting out. It took quite awhile to find the problem because it was lying loose and any time the tractor moved, it caused it to bounce around and gave you very unreliable troubleshooting symptoms.

So I got the birdbrain idea to go to the auto parts store and buy a time delay circuit breaker of 30 amp that fit the socket for the fuse. I don't know what the time delay curve was, but it didn't take long for me to smell smoke and I burned up a wiring harness using that time delay device.

Obviously I finally located the smoking gun....easy when all the wiring to the short had melted insulation, and solved the problem. In doing so, I separated all the loads that had no business being on a 30 amp circuit and put them on fuses rated for their wire gauge and have had no problems since.

So be careful defeating, or changing fuses.

My 2c,

Mark