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Only missing the crimped batt terminal now Bob, all other bits here
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/ John -
That's brilliant THANKS
I have uprated all wire to at least 16 amp (thin wall) think that is twice the rating of original wiring?
Now as there were no relays on original Imp system , what benefits is there for fitting to original parts that didn't have them in the first place .
If l remember rightly , when l fitted fog lights ,horns, on previous car l fitted relays and thicker wires on those parts.
Not sure of what amount of relays l would need to fit to improve system as l'd rather have relay boxes that would take a couple more than l would use , just to air on side of caution.
spot \ fog lights, horn ,fuel pump, electronic fuel valve, uprated blower (bilge pump), rear fog lights , are the extra things that will go on , have seen that you've put relays on headlights, is that because they're higher wattage now ? in that case l'll have to add those to my above list,
Like the look of these
Assuming two of these would fit together in same way as fuse box would clip to one (makes sense to me that it should) what say you.
Questions Questions Questions ???
Like to get my head around most of what l'm tryng to achieve before l get there.
Bob
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Bob
Basics of relays
2A switch and need to switch 4A, use relay to use small load to switch big one.
The relay load on a switch is around 0.1A 0.2A but depends on relay
Second purpose is what I usually refer to is point of load.
Rather than switch say 5A by running a wire 3m to front to switch and back another 3M of which both runs depending on SCA have some kind of voltage drop, fit a relay at back, the drop makes a difference at higher current.
On electronic systems it can make a huge difference, not so much on an imp, it helps, but an exmple would be if the eletronics would stop working at 11V, of the cable run loses 0.5V or poorly wired 0.8V then minimum battery voltage static, no alternator running on cold start would need to be minimum 11.8V plus losses battery to ignition switch and back.
Relays dont drop out normally until about 8V, so a relay fitted with as short a run at back as poss batt to load, no losses, better margin.
It is the plague of modern cars.
For things on an imp though.
I fuse and relay always, spots, dip, main, heater fan, wiper and horn and put a relay in for switched ignition 12V simply as I always see the ignition switch and the spade connectors on the heavier wires as a common point of failure. The switch due to the high current and the connectors as they are crap to begin with and the mechnical constraints of fighting with heavy gauge wires to massage it into place always leaves the mechanical integrity of the connections in doubt for me, seen then heast so much to melt the insulation. Horrid.
Yes 4 blade N/O Type A relays are common.
It just takes a little bit of thought and planning on how to use them, especially as regards how the coil is energised.
They can also keep the wiring weight on clusters and controls much lighter and tidy as the heavy supply is never wired in, like say the horn.
The always on 12V supply goes to the contacts AND looped to one end of the coil at the relay. You then switch the other end of the coil to gnd to energise the relay. You only need to run the heavy supply to the relay, you can use say 1mm wire for relay control.
OR
You can control the relay by having one end of coil always to GN at the relay, and switch a supply to the coil seperately, more useful for items that should not be used with ignition off.
Loads of options Bob.
Like I said the rear relays on mine are pretty much a waste of time except point of load saving as they are LED, I think they switch 350mA or so, but unlike filament lamps which will work from 3-15V, leds will drop out usually at 10V
Yes, the headlights are one issue, spots same 55W each, 110/ is nominal 9+ A so a fair load,
Heated screen I measured at 17, they quote 20/25A fuse
John
/ JohnComment
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Reading contradictory information in various electrical suppliers documents , at the moment majority of cables through sills are 16.5 amps, my intention was for seperate loom at front and back .
My way of thinking (worrying) is 16.5amp cable to supply lights etc via relays good enough , considering l'm using same cable just to switch the relay? (at the moment)
My new thought is (tell me if l'm wrong) upgrade feed to lights etc via relays to 25 amp.
Two reasons , if l use different size cable it's easier to differentiate relay cable, when both are same colour, from relay switching cable, and secondly it's upgrading power cables (overkill)?
Rather be SAFE than SORRY cost of doing so is immaterial.
BobComment
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Bob
Ah yes, the great debate
Basically cable is rated at X amps, X volts based on X temp (usually ambient) and you have to derate based on temp. The Imp runs its wiring beside the heater hose and tends to be
What they dont mention is that it should also be derated when in a bundle.
I have done some lists and Mike started as well. but here goes.
This is VERY approximate and perhaps rounded up from memory
Heater blower motor is 5A
Horns are also about 5A
Side lights (front and rear and number plate x 2) based on 5 x 5W (2 front 3 rear) lamps is about 3A
DIP Beam about 4A per side so 8A total
Main Beam about 6A per side so 12A total
Spots, if they say 60W divide it by 12 and thats 5A per lamp, if they are 100W then that would be 9A per lamp.
Brake lights (2 x 21W) 4A
Each dash or indicator lamp is about 2W, so 0.2A
So to light the dash and say 4 external gauges thats 1A, use LED for all except ignition lamps will drop that to 0.1A or so.
Interior light is about 3W for standard festoon lamp, 0.1A for LED
Relay coils, every relay coil you switch is about 0.2A so no benefit.
Fog light (1 x 21W) 2A
Reverse lights (2 x 21W on Wipac kit) 4A
To be honest the standard imp harness is pretty well designed, except early ones which screwed up some wiring leaving things live that should not have been (no flash backs Dave Lane )
My reason for the relays at the back Bob was to reduce the loop, if I took power from back of car to front to a switch then front to back again for the lamp (say reverse) thats about a 5M round trip.
Now all just pulled from my head and rounded there or there abouts !!
no comments on state of my head please fellas however tempting
Cable loss on 1.5mm CSA would be about 0.7V
The 12V I started with is now 11.3 @ 25 Deg by time I run it through the harness and I have two wires running in a loom both carrying 4A.
Heat that to 60 deg its worse
Say using a 55W spotlight for reverse (classic look) at 5A thats 0.8V
Loss would be about 0.02 ohms per M
How does CSA influence that
Cable loss on 2.5mm CSA would be about 0.3V
The 12V I started with is now 11.7 @ 25 Deg by time I run it through the harness and I have two wires running in a loom both carrying 4A.
Heat that to 60 deg its worse
Say using a 55W spotlight for reverse (classic look) at 5A thats 0.4V
Loss would be about 0.01 ohms per M
So increase CSA is one way to go, physically though its harder to work with.
Second possibility is to reduce the loop.
Same again below but using a relay at back, only 1M loop
Cable loss on 1.5mm CSA would be about 0.1V
The 12V I started with is now 11.9 @ 25 Deg by time I run it through the harness and I have two wires running in a loom both carrying 4A.
Heat that to 60 deg its worse
Say using a 55W spotlight for reverse (classic look) at 5A thats 0.1V also (rounded)
Loss would be about 0.02 ohms per M
In this case upgrade to 2.5mm CSA, is it really worth it ?
Cable loss on 2.5mm CSA would be about <0.1V
The 12V I started with is now pretty much 12V @ 25 Deg by time I run it through the harness and I have two wires running in a loom both carrying 4A.
Heat that to 60 deg its worse
Say using a 55W spotlight for reverse (classic look) at 5A thats <0.1V also
Loss would be about 0.01 ohms per M
Using a relay here makes sense to me
- 1 wire in long harness instead of two
- The one wire is only relay control 0.2A so 1.5mm will do
- The wiring from fuse to relay and relay to lamps can also be 1.5 CSA.
- The lamp is supplied with a slightly higher voltage.
Just a word of warning on LED replacements, especially on hazard / indicators and side lights.
LED lamps have a drop out voltage and most tend to be around 9-10V so, imagine a dark country road and your stuck
Unlike filament lamps which will simply just get dimmer as the battery goes to zero, when the battery drops to 9-10V (or the led assemblies drop out voltage) your led lamps will just go off, no light.
I await the corrections
/ JohnComment
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Right THANKS for that , bit over my head but never mind .
Already have relays with headlights that came as set, now thinking ,spot lights, horn ,blower, fuel pump, wipers, ignition switch all on relays , so 6 in all to get, looking at 2off bank of 4 relay block .that way there's a couple spare if needed
Relay in rear for rear fog lights, and reverse lamp , how does that sound ?
BobComment
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Bob,
Back, I would do (or at least provision for)
Fog, Reverse,
? heated screen
The ignition, brake lights etc can just be via fuses off the switched 12V in engine bay.
Fuel pump needs some care, you will need a saftey cut out, basically a relay interlocked to a signal that shows the engine is running. In addition you should add an inertia utout in series with the pump. So either the inertia cutout will shut fuel pump off almost instantly or the pump cuts out when engine stops.
Up front
Wiper
Heater blower
Horn
If using halogen conversion, dip and main beam
? Heated screen ?
John
/ JohnComment
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Nicely timed input there Dave Not Child Support Agency then, Yes l looked it up
Thanks
Heated screen, No, yes hadn't got around to cut out yet.
I AM getting there , REALLY l am.
Relay for ejector seat?
BobComment
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Ejector seat and rocket launcher, relay is required yes.
/ JohnComment
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on way bob and a few extras
Hopefully my current lack of dexterity has not caused any issue.
/ JohnComment
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Oh goody ,more toys , THANKS
BobComment
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All good stuff there John, Most alternators run at 13.8 - 14.1 ? so even with cable loss will that leave all components running at 12 volts approx so all will work as should?Comment
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Mike
Its all there or there abouts, the wire loss is the only constant really
12/24V calcs in my head (as its a standard voltage for me) id you add in decimal places it gives me a headache
To be honest I enjoyed the maths a bit for a change, will likely be doing more while my practical abilities are limited./ JohnComment
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Can you open a can or BOTTLE?Comment
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