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For what its worth, looking at the fuse spec'd out in the TM is rated for 125VAC 
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I'm an idiot!!! - Fermont MEP-802A 5kW
- Thread starter 4x4nutz
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As a general rule an AC fuse can be used in a DC application as long as the DC voltage is < 50% of the AC voltage rating of the fuse.
The one spec'd out in the TM is O.K. to use up to 60 volts DC.
The one spec'd out in the TM is O.K. to use up to 60 volts DC.
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Did not know that. Thanks for the info.
loosegravel
Just a retired mechanic who's having fun!
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I wouldn’t want to use the self resetting circuit breaker that I mentioned earlier in an AC circuit without having it secured and encased. Something about having exposed terminals in an AC circuit doesn’t appeal to me
120 VAC hurts! 24 VDC doesn’t hurt at all
120 VAC hurts! 24 VDC doesn’t hurt at all- 557
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| Fuse Trade Size | 3AB |
| Current | 30 A |
| Voltage | 250V AC/125V DC |
| Breakthrough Current | 1,000 A @ 125 V AC 400 A @ 125 V DC |
Only downside is made in China. But we need to choose our battles sometimes...
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I can't seem to find a breakthrough amperage rating on the Eaton OEM one, but the alternate Ive bought before (BK/ABC-30-R) shows an interrupt rating of only 200A... so I think that McMaster fuse might not blow when you want.
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200A is the listed breakthrough current on that item:
| Current Rating: | 30 A | |
| Fuse Type: | Fast Blow | |
| Fuse Size / Group: | 3AG (6.3 mm x 32 mm) | |
| Voltage Rating AC: | 250 VAC | |
| Voltage Rating DC: | 125 VDC | |
| Interrupt Rating: | 200 A |
But the interrupt or breakthrough current is the maximum current the the fuse can interrupt.
Not my words here:
“Interrupt rating” is not the same as “ampere rating,” even though both these are dealing with current values.
When reading technical data about a particular fuse you will see symbols or rather abbreviations such as I.R. or IR which refer to “interrupt rating.” Other abbreviations could be A I.R., A IR, or kA I.R. which is “amperes interrupt rating” or “kilo amperes interrupt rating” respectively.
Given a particular rated voltage, this current rating refers to the maximum amount of instantaneous current that can be interrupted safely without explosion or damage to the fuse link carrier, such as the cartridge or tube. This interruption of current flow can occur in fault or short circuit conditions. This current rating has been approved through standardized tests.
Interrupt rating is also referred to as “breaking capacity.”
In other words the fuse from McMaster is a more highly rated fuse - thus the "3AB" rating vs "3AG".
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THANK YOU gentleman for helping me get me 802A going again. Runs great, just need to get that oil pressure gauge fixed or replaced. It worked fine until we had the battery arc issue. Is it possible it blew the gauge when the batteries arced?
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Entirely possible as the arc would have been on the DC circuit, which this gauge also is. There are testing methods in the TMs for the gauges to confirm if they are good or not.
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I will try to replace it first.
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Firing the Parts cannon can fix problems... but not always. You could always just download TM 9-6115-641-24 if you don't have it yet, and reference PDF Page 113 to know for certain (for no money out of pocket):
nextalcupfan
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Agreed, at this point you don't know if its the gauge, sending unit, or both.
Ray70
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You guys really go deep into fuse selection! many many time I just went to my assortment of glass tube car fuses and grabbed a $.25 30A 1/4 x 1 1/4 AGC fuse, install it and done!
On the oil gage situation I see someone already changed the oil pressure gage, I'd double check the wiring and check the resistance on the sender, that should give you the answer.
On the oil gage situation I see someone already changed the oil pressure gage, I'd double check the wiring and check the resistance on the sender, that should give you the answer.
loosegravel
Just a retired mechanic who's having fun!
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Pretty simple with a one wire sender. This works for any gauge. Ohm check the wire from the sender to the gauge. If that’s good, with the wire disconnected from the sender and the gauge supplied with power, the gauge should be pegged on the high side. With the wire disconnected from the sender and then grounded the gauge should be pegged on the low side.
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The gauge actually goes down when I apply power....what's up with that?
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Where is that sending unit for the oil pressure gauge located? The diagram on the inside of the door does not really show anything, and there's no photos on the TM.
loosegravel
Just a retired mechanic who's having fun!
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The oil pressure sending unit is located on same side of the engine as the fuel pumps. It’s remotely located right above the fuel filter.
loosegravel
Just a retired mechanic who's having fun!
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YOU....are the man!
loosegravel
Just a retired mechanic who's having fun!
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The two wire switch is for low oil pressure shut-down. It doesn’t affect the gauge. The bell shaped sender with one wire is what works the gauge. It’s basically a variable resistor that changes it’s “R” value when the pressure increases. If you disconnect that one wire and turn S1 on, the gauge should go high. If you ground that one wire and turn on S1, the gauge should go low. If that doesn’t work, then ohm check the wire from the gauge to the sender. If that’s good, then your gauge is not functioning.