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Electrical connector ratings - working out
tims31 - 27/8/15 at 04:41 PM

I am looking at fitting AMP superseal waterproof connectors on the front of my car to connect up the headlamps and indicators etc but how do you work out what is the correct rated plug? They are rated at 14 amp and 20 amp connectors but how do you work out what the max power going through these would be ie. what is the standard rating for a headlight bulb plus indicators etc.

I just want to make sure I get the correct connectors for what I need.

Ta

Brook_lands - 27/8/15 at 04:59 PM

Add up the watts and divide by the voltage (12v)

55w headlight bulb takes 4.6 amps

Indicators are 21w and take 1.75 amps

Sidelights are usually 4 or 5w so about 0.5 amps

[Edited on 27/8/15 by Brook_lands]

gremlin1234 - 27/8/15 at 05:12 PM

the connectors should be at least the rating of the fuse for the circuit.
edit: you may also need more than one 'earth/chassis' connection

[Edited on 27/8/15 by gremlin1234]

Smoking Frog - 27/8/15 at 05:41 PM

Really depends on what bulbs are fitted, H4 headlight bulbs are 100/90 Watts (7.2A/6.5A) or 60/55 Watts (4.3A/4.0A). But a 14 amp connector would be OK for either (assuming a connector for each side).

Edited to say
amp = watt / volt

[Edited on 27/8/15 by Smoking Frog]

tims31 - 27/8/15 at 07:16 PM

Great, fantastic replies as always guys.

I can now at least sit down and work out to be on the safe side.

bi22le - 27/8/15 at 08:34 PM

If your getting close to the limit, split the earth as suggested.

The max rating will be across 1 pin. So if all of your lights are on at once then the pos supply will be split across all of the seperate pins, the single earth return will be the weak link.

tims31 - 27/8/15 at 10:01 PM

quote:
Originally posted by bi22le
If your getting close to the limit, split the earth as suggested.

The max rating will be across 1 pin. So if all of your lights are on at once then the pos supply will be split across all of the seperate pins, the single earth return will be the weak link.


Err, confused now I thought I had it, are you saying that the rating of say 14 amps is for one pin? I thought what people were saying is the rating for the whole plug so 7 amps for the headlight plus say 5 amps for the indicators is 12 amps, is it that the earth if combined for the two will be 12 amps and therefore close to the 14 limit for an individual pin? What your saying is that I can have each wire or pin up to 14amps so take care not to exceed 14 amp on the earth pin and split out to separate pins if necessary?

Sorry to be dumb on this but I want get it right, I know what damage can happen if I get it wrong.

Thanks

peter030371 - 28/8/15 at 06:58 AM

quote:
Originally posted by gremlin1234
the connectors should be at least the rating of the fuse for the circuit.
edit: you may also need more than one 'earth/chassis' connection

[Edited on 27/8/15 by gremlin1234]


To right! Work out your fuse ratings and then make sure your connectors and wires are rated higher than this ;-)

If your fuse is rated higher than your connectors or wire then if you get a fault the fuse won't blow in time to protect the loom which could melt or burn

Smoking Frog - 28/8/15 at 09:00 AM

quote:

What your saying is that I can have each wire or pin up to 14amps so take care not to exceed 14 amp on the earth pin and split out to separate pins if necessary?

Yes you've got it.

One other thing is that the headlight dipped and main beam are not normally on at the same time. So the earth cable could the same size as the main beam cable, obviously this may have to be larger if other things are sharing the same earth.

DJT - 28/8/15 at 02:51 PM

With the engine running, the battery voltage will be more like 14v than 12v. Might not make a big enough difference to your calculations to need to step up to the next size connector.

tims31 - 28/8/15 at 05:40 PM

Ok, at least I have confirmed that now so I could probably safely have the Dip beam, side light and Indicator going through one four way connector although I will double check once I know for certain the bulb ratings, I guess the six way connectors may be ok to connect up the main beam too so long as I used maybe two earths through the six way.

Thanks for all the help guys...