Suspected Regulator Fault within 18ACR

SydneyRoverP6B

Well-Known Member
Staff member
#1
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.
 

SydneyRoverP6B

Well-Known Member
Staff member
#2
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.jpg 20210814_085724.jpg 20210814_100033.jpg

Ron.
 

jp928

Active Member
#3
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.
 

Demetris

Well-Known Member
#4
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.
 

SydneyRoverP6B

Well-Known Member
Staff member
#5
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.
 

jp928

Active Member
#6
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.
 

SydneyRoverP6B

Well-Known Member
Staff member
#7
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.
 
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