Alternator alternatives

herbie

herbie

Member
Hello All,

Currently getting 12v on one of those cigarette lighter voltage checkers and slow indicators, alternator is about 9 years old, battery is a year old. I’m guessing the alternator is at fault, belt is tight etc. is there a better alternator nowadays than the 18acr one?

many thanks.
 
9 years? The alternator should last at least that long. As @roverp480 says is the ign light working. Test across battery terminals with engine idling, you should see at least 13.7v, higher is better. If you see that at the battery with the engine running it’s time to check earth straps for tightness. Also check battery terminal clamps, also check the condition of the cable going into the battery clamps. I had the same problems of low starter speed, slow blinking etc and it was due to corrosion where the cable was clamped to the terminal clamp (if that makes sense?).

As to your other question, I switched to a Lucas A127 for a Defender this year after my old AC11 alt died on my 2000TC. It eliminated a lot of relays (external regulator etc) and upped amps from 11 to 45. For an ACR I would imagine it would be an even easier swap.
 
Thanks guys, funnily enough I did check the earth cable and it was fairly Ropey the braids unwinding and a little tatty. I shall replace that first and see what I have. I will have to check if the ign light is illuminating, I haven’t consciously noticed it!
 
There is probably another earth strap between engine and body somewhere that should also be checked. particularly if the battery is earthed to the body.
 
Had a quick look before work this morning, the ign bulb does not illuminate at all when the key is turned, checked the bulb and that is fine….would an issue with the alternator cause that?
 
Hi, With the ignition on but not running, one side of the bulb gets 12V and the other earths through the alternator. Does it?

Colin
 
Before condemning the alternator you need to check the warning light wiring is complete. Disconnect the plug to the alternator and with the ignition on, bridge the thin wire ( Brown/yellow) from the plug to earth. The light should illuminate ( Warning -don't touch the large brown wire to earth) . If it doesn't ,wiring needs repairing. If it does its likely there is a fault with the alternator
 
Well, the problem was the smaller of the three wires in the wiring clip. The spade terminal had pushed up in the block and was not making a good connection if any, now have 13.7 V!
Thank you everyone.
 
It's always a good feeling when what looks like a major problem is solved with an easy fix :cool:

Goods news Herbie
 
What would be the standard AMP output on a 3500s alternator?

My bearings have a slight rumble and i would probably like to replace it rather than dismantle and replace the bearings.
 
ampwhu said:
What would be the standard AMP output on a 3500s alternator?

My bearings have a slight rumble and i would probably like to replace it rather than dismantle and replace the bearings.
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The 18ACR is I think 45amp and the 11AC is definitely 35 amp. Most modern replacements are 75amp so if you don't want to upgrade your wiring, then look for a 45/50A one at most.
 
PeterZRH said:
Most modern replacements are 75amp so if you don't want to upgrade your wiring, then look for a 45/50A one at most.
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Not quite true, amperage is from draw, so if you were to increase draw by, say, putting in halogen lights or some high draw electrical accessories then you’d want to upgrade the wiring.
 
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sdibbers said:
Not quite true, amperage is from draw, so if you were to increase draw by, say, putting in halogen lights or some high draw electrical accessories then you’d want to upgrade the wiring.
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Well, if you ever had a heavily discharged battery then that would do it too. So you still need the capacity in the cabling. Halogen lights are more or less the same as fixed beams. What would load it would be my plan for electric steering.
 
PeterZRH said:
Well, if you ever had a heavily discharged battery then that would do it too. So you still need the capacity in the cabling. Halogen lights are more or less the same as fixed beams. What would load it would be my plan for electric steering.
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That’s true on the steering, but I would imagine that would be new wiring anyways. Draw on battery discharge could be replaced with a larger cable for sure.
 
sdibbers said:
That’s true on the steering, but I would imagine that would be new wiring anyways. Draw on battery discharge could be replaced with a larger cable for sure.
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The 11AC has one cable and the 18ACR variants have 2 connections in a double block connector - the so called Lucas/Bosch connector which also includes the exciter cable - in both cases these are 1/2" spades internally. I assume this is because either the limit of the spade connector is exceeded or it can be optional i.e. you can have a wiring loom for a single cable and then simply add an additional one for the higher output alternator. Technically it's a poor solution due to modes of failure. It's better the whole thing fail than one cable is lost and the whole output goes through one cable. The ford solution with a single loop terminal to a stud is superior.

I'm going to use what was the original alternator cable. Because when I upgraded to the A127, I didn't want to cut any original cable added 2 new runs of cable through the firewall to the post on the floor. The original is isolated at the moment. This means I can re-use the original alternator cable to power the PAS - if it is thick enough - this was in the back of my mind when doing this - yes I could spur it directly from the alternator but this isn't so easy to do neatly due to the connector. Cable ratings are of course usually given as continuous and in long lengths - typically 100ft or 1000ft as they are AWG - American wire gauge and they do everything in feet. It is perfectly acceptable to overload these quite considerably for very short periods on short cables as there is no issue with OVERALL heating and hence safety. What becomes a problem then potentially (every pun intended) is voltage drop. Hence lighting cables and screen heaters are heavier than expected as they are continuous loads and something like the PAS lighter than you might think as the load is "peaky" - 98% of the time the load is <10amps but can be 70-80 for short bursts.. A 6ft 10AWG wire for example which is typically rated at 30amps running overloaded to 60amps will dissipate less than 10W (it's an easy one to remember it's 1ohm per 1000ft) . So it might get warm to the touch after a minute or so say. When you hit that 60amps on say a 6ft cable (it'll be shorter) you get towards 0.4V drop which is more than 5% which we use as a guideline. Of course auto electric systems are not precise operating in the 12-14.4V range, so while the engine is running, this will still be more than 12V at the load. I'm guessing the steering in the original installation is no heavier than 8AWG which is rated for 55amps possible even as low as the 10AWG.
 
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