Suspected Regulator Fault within 18ACR

SydneyRoverP6B

Well-Known Member
Staff member
I noted on Sunday last that my Rover's ammeter was wavering slightly about the null position whereas normally it is perfectly still. The voltmeter will normally read between 13.5 and 13.8 volts (0.5 volts less than the voltage across the battery) was reading 14 volts. The ignition warning light was behaving erroneously, either staying illuminated once the engine was running, then gradually fading out as the engine revs increased, or behaving normally to a point but then illuminating simultaneously with the headlights being switched on. In both scenarios, the ammeter showed no discharge, and the voltmeter remained on 14 volts or even higher. From my experience this behaviour is not symptomatic of brushes, nor is it typical of problems with the bridge rectifier. Instead to me they suggest the regulator is at fault. My plan is to replace the latter tomorrow, then following a test run I will report back with the findings. The existing and the replacement regulators are branded Cargo, which is a product originally manufactured by the Danish company Holger Christiansen. In 2008 the company was acquired by the Bosch Group, with the Cargo regulators now manufactured in China. My Rover still runs the original factory fitted alternator, albeit with different brushes, slip ring, bearings, and regulator. It has seen a total of over 407,000 miles (655,270km) of service running with regulators branded as Lucas, Ingram, and Cargo. Of these, the Cargo products have been clearly the most reliable.

Ron.
 
Well as it would transpire, the regulator was not the problem. Changing this made no difference, so I took the new one back out again. With the engine idling, voltage across the battery measured in the order of 14.3 V DC and 0.5mV AC. Changing the rectifier was next on the list, so this morning I removed the 47 year old original and fitted a Cargo item. Starting and road testing revealed that this had been the problem as functionality had returned to normal. A very pleasing outcome! The photos illustrate the old rectifier and the new one after fitting.20210814_085538.jpg20210814_085724.jpg20210814_100033.jpg

Ron.
 
Terrible life you are getting out of that alternator Ron! Soon it will be almost the old man's axe! Most encouraging for my 18ACR. All the Lucas smoke is still captive.
 
It's nice that you can still get reliable parts for these. The reason that i have thrown away a 16 ACR was the frequency that i had to replace regulators. As far i remember they were all genuine Lucas parts, or so it said on the tin.
 
Terrible life you are getting out of that alternator Ron! Soon it will be almost the old man's axe! Most encouraging for my 18ACR. All the Lucas smoke is still captive.

Haha so unreliable isn't it John :LOL: Good to hear that your 18ACR is holding captive all that Lucas smoke. It is always a good idea to carry a spare regulator and some brushes with you, especially when you take your Rover on holidays. If you need to change either, the longest time spent is removing the alternator from the engine, and then refitting it.

It's nice that you can still get reliable parts for these. The reason that i have thrown away a 16 ACR was the frequency that i had to replace regulators. As far i remember they were all genuine Lucas parts, or so it said on the tin.

It is indeed Demetris :) I am very pleased with the quality of the Cargo branded parts. I do agree, the Lucas regulators would typically only last a couple of years before they would play up and need replacing.

Ron.
 
Being a bit picky, isnt that part strictly the recifier, from AC to DC? Or is a regulator incorporated in it? These days I usually see initial charging as high as 14.7V, tapering down to 14.1V as the battery fills. Some alternators are now controlled by the car's ECU, rather than a built in regulator.
 
Being a bit picky, isnt that part strictly the recifier, from AC to DC? Or is a regulator incorporated in it? These days I usually see initial charging as high as 14.7V, tapering down to 14.1V as the battery fills. Some alternators are now controlled by the car's ECU, rather than a built in regulator.

Yes, the bridge rectifier consists of 9 diodes John that remove the negative half period of each sinusoidal wave. The waveform would I expect be smoothed by one of more capacitors which likely reside within the regulator. The rectifier and regulator are distinct items within the alternator. The regulator is the shiny rectangular box in the one of the photos. Its function is to maintain the output voltage between preset boundaries. The Cargo voltage regulators have two wires along with some of the Lucas and Ingram products, whilst those Lucas regulators that had a built in battery sensing function came equipped with four wires.

It is also my understanding that the UK market 18ACR alternators did not have air vents within the black plastic cover, whereas the Rovers for the Australian market all came with such due to the hotter climate within this country.

Ron.
 
Ron, hoping I can pick your brains on alternators! My 3500s has an 18ACR fitted, when running around 1500rpm, voltage across the battery 14.7/14.8v, doesn’t drop too much when lights, heater etc switched on. Battery showing 12.6 volts with engine off.
recently, the engine has begun to switch off if the rh indicator is used, or the brake lights go on, or the heater blower switched. I’ve checked fuses and earth connections and all seems ok. I’m now stumped and before I call an auto electrician, thought I would see if there are any other suggestions.
many thanks.
Scotty
 
Hi, With out treading on Ron's toes, those are all ignition controlled items so I would suspect the ignition switch connections or internals. If you're feeling brave dismantle,clean and inspect the contacts or better still replace the switch.

Colin
 
G'day, Scotty

I agree with Colin. The common denominator is the ignition switch. The switch is behind the barrel, and to be honest it is quite a fiddle to remove and refit.

Let's know how you go.

Ron
 
Thanks again Guys for your help. First step to get a new switch and go from there. I’m heading to UK in three weeks so will bring one back and have a crack. There may be a delay with any update!
cheers
 
Hi Guys, much-delayed update on replacing the ignition switch. Managed to get a 7 wire replacement from Wadhams after confirming the old one had 7 wires. However, it seems the other end of the connector only has 4 wires. I suspect I’ve ordered the wrong switch, but thought I would ask the brains trust before I order another. I’ve attached photos of the old switch, the ends of the Wadhams replacement switch and the existing receiving end of the connecting block.
You were right, replacing is less than easy and requires some new swear words. Thanks in advance for any guidance.
 

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Scotty, year and chassis no will help - seem to be a few variations in the switch. Which part no did you finish up with?
 
Hi - agree about the variations! It’s a 1974 3500S, chassis number 48200796C. The OE part number I bought was 586750. I’m thinking if I take the new switch back out again, I might be able to map the wires from the old switch, but the colours are not all the same. Might be easier just to order another one. Cheers.
 
My parts book says a 482 ...C chassis should use switch 586419. The 9 is unreadable in the 1977 book, but is visible in the early book. My car is also 74, 482.....D,
 
Many thanks for that, that’s a huge help. I think I’ll just order another one with the right part. Wadhams have that in stock too; someone in the local club here might be able to use the version I bought. Thanks again.
cheers
 
Being stubborn, I stripped the new switch back out and mapped the terminals against the old one. The colours on the new Wadhams one are actually very close to the original, you just have to peer very closely! So have taped up the leads not being used (copied from the old switch) and reinstalled, connecting the remaining leads to the existing connector block. Tested and seems ok so have rebuilt everything and now hoping for the best.

if it helps anyone else, to get the old switch out, I removed drivers glovebox, all the front switch panels, pulled out the switches and wiring and also removed the steering column. I managed to leave the steering wheel on the column. Once the old ignition switch connector block was split, the whole steering lock and switch assembly came out with the steering column. It’s then easy to swap the old and new switches over. It was a bit of a fiddle but it got me enough access to change things over.

Thanks again for all the help and guidance. Hopefully now a chance to drive it again after weeks off the road.
Cheers
 
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