Can someone with more electrical knowledge tell me where to go with this fuse sizing question?
Which fuse for 14 gauge wire on A/C? (1 Viewer)
- Thread starter knuckle47
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Can someone with more electrical knowledge tell me where to go with this fuse sizing question?
A quick search says 14g wire is good for 15a. (?)
It may be this one:
It's weird that the control panel doesn't appear in the listing except for just a second at the start of one of the videos.
There are pics of a very similar unit in this (2013) thread. If you google image search on the pic of the underdash unit from there it turns up quite a few hits around the internet. Seems to be a fairly popular unit.
It may be this one:
It's weird that the control panel doesn't appear in the listing except for just a second at the start of one of the videos.
There are pics of a very similar unit in this (2013) thread. If you google image search on the pic of the underdash unit from there it turns up quite a few hits around the internet. Seems to be a fairly popular unit.
To size the fuse correctly you will need to have the fuse curve, starting and running current of the load, published resistance of the wire, and length of the circuit. If you don't have that, it is guessing. I can confirm my 40 series OEM 12V evaporator fan pulls 6.2 Amps running on High. It pegs my 10A DC ammeter on starting but I guess it is pulling 15-18 amps during start. Find a fuse that can accommodate that and still protect your wire. Automotive wires, best I can tell are designed to provide < 3% voltage drop to the load, if it can do that it will withstand the heating from the load current (I2R losses). The fuse also has to protect for short circuit current and overload conditions. I have seen some "rule of thumb" charts on automotive wire sizing but nothing in a standard. I use the NEC methods for designing power cables for industrial applications.
Here is an example curve set for Littlefuse 3AG slow blow fuses. If you operate to the left of the line, the fuse should be ok and not open prematurely. The wire/cable thermal damage curve must be to the right of the line. You also have to consider all fuses don't fall on the line, there is a tolerance band on either side, some fuses will open earlier, and some will open later than the line.
If this fuse also powers the compressor clutch, you will need to add that as well (4-5A)?
Here is an example curve set for Littlefuse 3AG slow blow fuses. If you operate to the left of the line, the fuse should be ok and not open prematurely. The wire/cable thermal damage curve must be to the right of the line. You also have to consider all fuses don't fall on the line, there is a tolerance band on either side, some fuses will open earlier, and some will open later than the line.
If this fuse also powers the compressor clutch, you will need to add that as well (4-5A)?
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- #4
I was licensed in amateur radio in 1981. Used formulas for stuff like velocity factor and a ‘S’ load of others..not really Greek to me but …it’s Greek to me now. I’ll go with the 5A slo-blow and move on from there…thank you guys for the information. If we have heat as we did for the last few weeks, I’m gonna want to be sure it runs and can handle it
This is the wiring for an FJ55 AC system, pretty close to the FJ40 and other under dash type units.
KJ4BEB
KJ4BEB
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Fuses getting hot like that are usually caused by bad connections to the fuse, rather than the wrong fuse.
Check for corrosion and poorly crimped wires.
Measure the current its using with your meter and fit a fuse with a bit of head room.
I assume you must have a meter since you have a 40, right?
Check for corrosion and poorly crimped wires.
Measure the current its using with your meter and fit a fuse with a bit of head room.
I assume you must have a meter since you have a 40, right?
That Amoron one has an electric compressor 600W (assume total power draw) / 12 V is 50A.
Fuses are cheap, start with a 10A and see what happens. Then try a 15.
You could make a test lead, with a known fuse in series and dead short them. Waste a 5, 10, 15, ... until your unknown fuse blows. Ought to be able to get a good approximation of the value.
+1 for corrosion is more resistance ie heat.
Fuses are cheap, start with a 10A and see what happens. Then try a 15.
You could make a test lead, with a known fuse in series and dead short them. Waste a 5, 10, 15, ... until your unknown fuse blows. Ought to be able to get a good approximation of the value.
+1 for corrosion is more resistance ie heat.
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- #8
I have actually replaced that fuse holder for the one in the photo. I kinda thought the same thing. My biggest concern was just being able to replace the fuse that had the color indicator fallen off with one I can identify and just have extras should it be needed. My search has not been very helpful so far
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- #9
I am still looking for any schematic of this unit and the new “amazon” competitor seems to have this ….by the way, if you like receiving 5 texts a day TEMU is for you.
I ordered a few outdoor solar lights and I get way too many messages encouraging me to click for more discounts….on the other hand..they do have loads of stuff
www.temu.com
I ordered a few outdoor solar lights and I get way too many messages encouraging me to click for more discounts….on the other hand..they do have loads of stuff
Universal Underdash Ac Accessories | Temu Temu
on universal underdash ac accessories on Temu. on Temu to .
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- #10
So here’s the net result…. I plugged in a 5A spade lug fuse expecting it to NOT handle the startup load but… it works fine…let it run for 15-20 minutes…not issues. Placed a 7.5A and a 10A in the glove box since they were in my hand …also bought a load of the conventional glass fuses as the original fuse panel dictates..
Should be fully prepared for this chapter anyhow.
Should be fully prepared for this chapter anyhow.
