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US Equiv. to Lucas25A Fuse?
- Thread starter sammyb
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Sammy, you are better off using Lucas fuses if you are wired with British wires. That said, there is no really accurate conversion table for the fuses. A safe bet is cut the fuse size in half and use that number for an American fuse. They have different burn rates than Lucas fuses and a 25 amp American fuse could well torch your wires if there is a short or overload. The only purpose of a fuse is to protect your wires. Better safe than sorry. Order plenty of Lucas fuses in both sizes and keep them in the cubby.
Bill
Bill
Geo Hahn
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Here is an old post from elsewhere that I saved. Same answer as Bill's but with some explanation (and I agree about using Lucas fuses as they are also the right physical size).
==== quoting Odd H ====
A Lucas fuse is rated by what current it would blow at. Ordinary automotive fuses are rated by what current you can draw WITHOUT blowing them, or the maximum continuous current. They don't really specify at what current they'll blow...
Anyway, these old Lucas fuses of mine have both the Lucas "will blow at" rating, and the maximum continuous current rating, i.e. the normal rating labelled on them. [Or rather in them, because it is a small paper strip inside that carries this info. The more modern Lucas fuses have the info printed on the glass tube in an abbreviated form.]
So here's your equivalents:
Lucas 50 amp - continuous 25 amp
Lucas 35 amp - continuous 17 amp
Lucas 25 amp - continuous 12 amp
Lucas 20 amp - continuous 10 amp
Lucas 15 amp - continuous 8 amp
Lucas 10 amp - continuous 5 amp
Lucas 2 amp - continuous 1 amp
See the trend here? Each fuse is actually good for a continuous current that's roughly 50% of it's Lucas rating.
==== end quote ====
==== quoting Odd H ====
A Lucas fuse is rated by what current it would blow at. Ordinary automotive fuses are rated by what current you can draw WITHOUT blowing them, or the maximum continuous current. They don't really specify at what current they'll blow...
Anyway, these old Lucas fuses of mine have both the Lucas "will blow at" rating, and the maximum continuous current rating, i.e. the normal rating labelled on them. [Or rather in them, because it is a small paper strip inside that carries this info. The more modern Lucas fuses have the info printed on the glass tube in an abbreviated form.]
So here's your equivalents:
Lucas 50 amp - continuous 25 amp
Lucas 35 amp - continuous 17 amp
Lucas 25 amp - continuous 12 amp
Lucas 20 amp - continuous 10 amp
Lucas 15 amp - continuous 8 amp
Lucas 10 amp - continuous 5 amp
Lucas 2 amp - continuous 1 amp
See the trend here? Each fuse is actually good for a continuous current that's roughly 50% of it's Lucas rating.
==== end quote ====
I noticed the 25 is rated at 12 continuous on the paper.
Now all I have to do is figure out what is causing her to blow! I think there's a short in my fuel gauge, because it reads all over the map -- sometimes all full, sometimes all empty, and sometimes right on...In the past I've been able to push the guage and it would flicker to the right level.
Have you all ever heard of this happening?
Any way to test the gauge?
Now all I have to do is figure out what is causing her to blow! I think there's a short in my fuel gauge, because it reads all over the map -- sometimes all full, sometimes all empty, and sometimes right on...In the past I've been able to push the guage and it would flicker to the right level.
Have you all ever heard of this happening?
Any way to test the gauge?
dklawson
Yoda
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Visit www.britishwiring.com and specifically download the following page:
https://www.britishwiring.com/CAT20_21.PDF
You'll find the fuses you need. Buy extra for the glove box.
Smiths fuel gauges/senders fall into two basic groups, the early magnetic type which don't use the voltage stabilizer and the later bimetallic type that work with resistance heating and use the stabilizer. Generally the sending unit has at least one (green/black) wire. Sometime the sender has a second black wire going directly to chassis ground. It's a good idea to add a ground to the sender (or tank) regardless if you're experiencing problems with the gauge. To test a gauge or sender, disconnect the green/black wire at the sender and with the ignition on, ground the wire. On EARLY magnetic gauges, this makes the gauge read empty. On the more common later gauges (cars with voltage stabilizers) the gauge should read full. If this doesn't happen you have a gauge or wiring problem.
Since you're having shorting problems, you're likely going to have to dig carefully through the back of the dash and look for where the green/black wire connects to the back of the fuel gauge. Make sure the green/black wire isn't shorting out to ground somewhere on it's way to the tank. Also make sure that nothing is coming into contact with the solid green wire supplying either the fuel gauge or the voltage stabilizer (if fitted).
https://www.britishwiring.com/CAT20_21.PDF
You'll find the fuses you need. Buy extra for the glove box.
Smiths fuel gauges/senders fall into two basic groups, the early magnetic type which don't use the voltage stabilizer and the later bimetallic type that work with resistance heating and use the stabilizer. Generally the sending unit has at least one (green/black) wire. Sometime the sender has a second black wire going directly to chassis ground. It's a good idea to add a ground to the sender (or tank) regardless if you're experiencing problems with the gauge. To test a gauge or sender, disconnect the green/black wire at the sender and with the ignition on, ground the wire. On EARLY magnetic gauges, this makes the gauge read empty. On the more common later gauges (cars with voltage stabilizers) the gauge should read full. If this doesn't happen you have a gauge or wiring problem.
Since you're having shorting problems, you're likely going to have to dig carefully through the back of the dash and look for where the green/black wire connects to the back of the fuel gauge. Make sure the green/black wire isn't shorting out to ground somewhere on it's way to the tank. Also make sure that nothing is coming into contact with the solid green wire supplying either the fuel gauge or the voltage stabilizer (if fitted).
Sam-- I've just been thru problems with my turn signals and gas gauge. Saw no reason for the gauge to dysfunction and act strange either. Nothing was visible/touching, and it had recently worked. On a test trip to test my turn signals, I reached under the dash while waiting for a long traffic light and wiggled each fuel gage connection and bingo-- found the culprit. Later cleaned and reinstalled the connection on the back of the guage and no probs since. Also regarding the short--you might see if the wires/connectors on the bottom of the ignition switch are contacting the bottom of the frame for the center panel. I heard a loud snap/saw sparks when I was reinstalling mine. I added some additional insulation and pulled the ignition switch wires away more. Pete
Geo Hahn
Yoda
Offline
[ QUOTE ]
Now all I have to do is figure out what is causing her to blow! I think there's a short in my fuel gauge, because it reads all over the map -- sometimes all full, sometimes all empty, and sometimes right on...
[/ QUOTE ]
1. Here is the place with the scoop on the fuel gauge -- a very comprehensive site:
https://mgaguru.com/mgtech/electric/fg_01.htm
2. Re fuse length -- if you use a 20 amp BFE as a substitute for the Lucas 35 then yes, it will be longer. A 14 amp will be close to the correct amperage and I think is usually shorter than a 20. A 14 amp is plenty big enough for that 35a (Lucas) circuit on a TR3A unless you have added a *lot* of accessories (in which case you would probably fuse them separately).
3. First step in any electrical work is to disconnect the battery -- then no sparks.
Now all I have to do is figure out what is causing her to blow! I think there's a short in my fuel gauge, because it reads all over the map -- sometimes all full, sometimes all empty, and sometimes right on...
[/ QUOTE ]
1. Here is the place with the scoop on the fuel gauge -- a very comprehensive site:
https://mgaguru.com/mgtech/electric/fg_01.htm
2. Re fuse length -- if you use a 20 amp BFE as a substitute for the Lucas 35 then yes, it will be longer. A 14 amp will be close to the correct amperage and I think is usually shorter than a 20. A 14 amp is plenty big enough for that 35a (Lucas) circuit on a TR3A unless you have added a *lot* of accessories (in which case you would probably fuse them separately).
3. First step in any electrical work is to disconnect the battery -- then no sparks.
Hi Sammy,
Littlefuse makes the "GBC" series of fuses which have worked just fine in my TR7. As for the different rating systems, Im sure these are rated under the American system as Littlefuse in and American company.
Their produt offering is as follows;
GBC 5 (yellow)
GBC 8 (white)
GBC 16 (red)
GBC 25 (blue)
Their physical size is 6 x 25 mm
Littlefuse makes the "GBC" series of fuses which have worked just fine in my TR7. As for the different rating systems, Im sure these are rated under the American system as Littlefuse in and American company.
Their produt offering is as follows;
GBC 5 (yellow)
GBC 8 (white)
GBC 16 (red)
GBC 25 (blue)
Their physical size is 6 x 25 mm
I threw in a Carquest 10A fuse (figured I'd start on the safe side -- I also bought 15A,) and it's holding so far. I fiddled with the fuel gauge without taking it out, now it's reading FULL, although I think it should be a little under F. I guess I'll have to pull it and clean the contacts.
What makes me mad is that I bought I set of 5 10A fuses, and 3 of them had cracked/shattered glass. I guess all I need is one to work!
What makes me mad is that I bought I set of 5 10A fuses, and 3 of them had cracked/shattered glass. I guess all I need is one to work!
Geo Hahn
Yoda
Offline
[ QUOTE ]
...I fiddled with the fuel gauge without taking it out, now it's reading FULL, although I think it should be a little under F. I guess I'll have to pull it and clean the contacts...
[/ QUOTE ]
The TR3A fuel gauges are adjusted by loosening nuts on the back and sliding the 2 side magnets along their slanted slots... fiddly work best done with a set of test resistors or (in my case) with the sending unit on the bench too.
You can sort of test the sending unit by taking a long length of copper wire and bending one end into an 'ell'. With this you can either depress or lift the arm of the sender and observe the effect on the gauge (you can probably see the sender arm when you peer into the gas tank).
Of course, if you get no change on the gauge look for (as noted above) a broken connection.
...I fiddled with the fuel gauge without taking it out, now it's reading FULL, although I think it should be a little under F. I guess I'll have to pull it and clean the contacts...
[/ QUOTE ]
The TR3A fuel gauges are adjusted by loosening nuts on the back and sliding the 2 side magnets along their slanted slots... fiddly work best done with a set of test resistors or (in my case) with the sending unit on the bench too.
You can sort of test the sending unit by taking a long length of copper wire and bending one end into an 'ell'. With this you can either depress or lift the arm of the sender and observe the effect on the gauge (you can probably see the sender arm when you peer into the gas tank).
Of course, if you get no change on the gauge look for (as noted above) a broken connection.