fv1609

Dan, once it is fully warmed it should read no more than 180 deg F. If it is increasing beyond that the sensor is failing or the connections to it increasing in resistance as something warms up. I think at room temperature the resistance of the sensor is something like 200 ohms. If it goes open circuit or the lead/plug fails then the meter reading will go to maximum. So start prodding around with an ohmeter esp when it is reading high. Those catches need freeing up with WD40 or if that doesn't work some heat from gas of some sort. It is just a sort of rectangular block of steel tensioned by a lever spring. They are quite cheap to buy if all else fails. There was a fake RUC flying Pig that did the rounds on ebay a few years ago. That is now owned by a member of the forum in Portsmouth. So intrigued by this one you have heard about. Sadly the term "ex-RUC" in Pigs is used with the same enthusiasm to describe some Land Rovers which are said to be "ex-SAS";)

Gosh & I thought this was the biggest smile you could manage! Well you at least you've had a shave & got a nice clean shirt. So so I'm sure she's very special, well done:-D

As others have said, burning of the contacts of the IR switch was an established problem. To address this there was an EMER issued in March 1982 to introduce a relay to cope with the high current switching. It also included an instruction for removing the switch altogether if the IR facility was not needed. It was to be done in such a way that it would be straight forward to install a relay & a new switch if operational requirements dictated the use of IR in the future. Paul selecting the IR to ON means it kills all other lighting circuits except to the headlights which will have been fitted with IR filters.

Yes many thanks to Paul & all his helpers. Paul you must be exhausted by now, you were on the go every time I saw you. Rosie I didn't knowingly see you but today heat & pollen took its toll & was mostly spent in the shade lying under the Wolf. So next year the 60 years of the Champ celebrations I believe.

Bring your wellies.!!

Humbering in the hedge

Great Dorset Steam Fair & I would say more than 10-15 years ago.

Same here in the second edition July 1982. part no 599443 There is also Parts, kit, shuttle valve 2530-99-824-3020 part no SP2863

I often find that if at first you don't succeed give up! Then come back to it the next day when there is less adrenaline flowing & you have had a chance to reflect on things. Very often when I am waking up I can see my way round problems that were such a challenge the day before. I would ditch that that digital meter. I even have an expensive militarised Fluke digital meter & despite all the fancy features I rarely use it because it is such a pain. I prefer an Avo 8 & 12. But this is perfectly adequate for most tests & is unambiguous in performance. http://www.maplin.co.uk/general-purpose-analoguemultimeter-25414

Before you do anything drastic to yourself(!) or the generator, I would abandon the multimeter & get an analogue meter. Even a new £5-£10 will be quite adequate. Maplin & others have these budget meters.

That's the problem with digital meters is that there is no way of off-setting the resistance in the leads & prods. At least with an analogue meter you can adjust it to zero ohms with the prods connected. The other problem is that it can just display gibberish when you are not measuring anything! But in these generator test the overwhelming problem is that the ohms range on a digital meter is useless for testing diodes & it will give very high readings. A silicon diode needs to be forward biased with about 0.7 volts before it will conduct & demonstrate the properties of a diode. An analogue meter will bias it sufficiently to test it but I'm afraid digitals are a waste of time for these sort of tests.

Is your multimeter digital or analogue? Sorry I don't understand where you are measuring Sorry I don't understand what you mean I am in the process of expanding & clarifying the generator tests for a new version of ACU4. The basis of these tests were from Field & Base Repair EMERs. The impression it gives is that the diodes can tested individually as it describes tests that appear to subject individual diodes in turn to scrutiny. The problem is that the stator windings are very low resistance in the order of 0.05 ohms this in effect joins the cathodes of all three low power diodes putting them in parallel with each other. So when you do tests to P, T & R you are just testing 3 parallel diodes & should get identical readings. A failure in one will give the impression of failure in them all. By moving between P,T & R you are testing the continuity of each of the 3 main stator windings & at the same time repeating the tests on the paralleled diodes. Despite what ACU4 says the only way of testing an individual diode of any of the 9 is to remove the section of the generator that houses the diodes & the large connector. Then unsolder the soldered terminal of one diode at a time. You will also need to remove the end cover plate so that when you assemble it again the carbon brushes can be aligned into place. So I'm sorry it is not as easy as EMERs & ACU4 first indicated. I have spent 8 hours so far on the new version, but a long way to go yet. The points you raise are not a nuisance but help in fashioning improvements. In fact all of ACU articles have been in response to trying to help people & the queries arising help focus my mind:)

Ah but a late 2A will have a 90-amp system. Pleased that you will be keeping the real thing behind your toast rack.

You'll never get fit now Paul riding around in that conveyance all day

Yes Wayne you are correct. The 40-amp alternator AC724/1 has no internal rectifier of any type & relies on the external selenium full wave rectifier. In the event of the selenium rectifier failing it would of course be possible to cook up an equivalent bridge rectifier using silicon diodes. They could be discretely mounted into the fins of the old rectifier preserving the look of a toastie. I feel a toastie with no rectifier behind the grill is a bit of a let down. The 90-amp alternators of course have integral silicon rectifiers.

Well the obsolete Maplin diode was 1N5408G, which was a glass version of 1N5408. This is still available at 29p however the maximum working voltage has dropped from 150 deg C to 125 deg C. Although it can withstand short term high temperature soldering, given the heat in the vicinity of engine, it would be best to have as high a temperature rating as possible. Moving to 6A diodes, the P600J is rated at a PIV of 600v & a maximum operating temperature of 150 deg C. The price rises to 99p but that is still good value. http://www.maplin.co.uk/6a-silicon-rectifiers-46413 Click on "Specifications" Although this is Hobson's choice having a diode rated to withstand a much higher current means it will not be struggling & overheat. These 6A diodes are rated at 600PIV whereas the original Lucas diodes were rated at 400PIV so there is an additional safety margin. It may seem curious that diodes with such a high PIV are used, but it has to be remembered that inductive loads (coils, motors, alternators etc) can produce high voltage transients & can destroy diodes if their PIV is too low.

I'm updating ACU, went to the Maplin site to check on the diodes to find "This product has been discontinued" Not very helpful so I'll start looking again.

Thank you for documenting that, although I heard a lot of what they said, I had forgotten much of it! Nice to have it tabulated & it might with time help displace some of the misconceptions that are churned out by certain "reference" sites.

Last year I had 4 emails from Paypal telling me that my account had been suspended. It sort of looked genuine but each gave a difference reason for the suspension & none of the reasons rang true. I didn't follow the links but logged into my account to find that it was suspended giving yet a further reason for the suspension & blaming me! Repeated emails were met with automated replies that bore no relation to my problem & the queries that I had raised with all these varied reasons. I rang them up to find that my foreign bank had unilaterally changed my sort code in their long drawn out assimilation of my British building society based account. It was appalling that my bank did not tell me & it is equally appalling that Paypal not only couldn't tell me the reason but chose to send multiple emails giving varied & spurious reasons for the suspension. It is regrettable that there was no tone of understanding or conciliation from the company or by the person that I contacted. They didn't seem to grasp that multiple emails out of the blue with spurious statements relating to the suspension would naturally be regarded as suspicious which is why declined to respond to these emails directly. A bit like the attitude the banks have if they phone you, I am expected to prove who I am if I phone them but they cannot grasp that if they phone me I want them to prove who they are. They make no effort become obstinate & off hand recording on my notes that I was uncooperative. What do they expect? Anyway better not start ranting about arrogance in the banking system as I'll be here all night.

The ISPL makes no reference to it being special with a left hand thread. So once the cotter pin is removed it should undo turning anti-clockwise.

You don't need a diode pack, you just need to replace the 3 small relatively low power diodes, which are actually rather insignificant in size. I see I have mislabelled the pic in ACU. When you look at the 3 diode packs each has 3 studs. The studs at each end of the trio are the high power diodes. They are functionally identical to each other although one in each trio is the reverse polarity of its partner. This is because they share a common heat sink so one has the cathode (-ve) on the stud & the other partner diode has the anode (+ve) on the stud. But the central stud of the 3 studs is not a diode it is the stud attached to the stator winding. So my picture is misleading & I need to correct it. The low power diodes have the cathode to the stud connecting each directly to the heat sink & each stator. The original low power diodes were Lucas DD3026A = CV8871, these are obsolete & were replaced by 5961-99-833-9958 = FV636048 which are used by a number of vehicle manufacturers. No doubt if I gave a list of part numbers one could spend a lot of time chasing distributors reluctant to deal with an individual customer & wanting to charge hefty prices, fancy handling charges to cover all the invoices a paper work. So I would forget that. There is nothing special about these diodes, the DD3026A is just a silicon diode rated at 1.5 amps able to withstand a PIV (Peak Inverse Voltage) of 400 volts. In order to dissipate heat in these early diodes they had to be bolted to a heatsink. Modern diodes are more robust looking in the Maplin catalogue there are diodes which look man enough AND THEY ARE ONLY 29p As long as they don't get hotter than 150 deg C they don't have a heatsink stud & can just be wired in. They are rated at 3A & 1000 PIV. http://www.maplin.co.uk/3a-glass-passivated-rectifiers-46407 http://www.maplin.co.uk/media/pdfs/Module%2046407.pdf

Sean I have seen regulator modules that have actually melted. But I think Mk 4 panels are electronically more robust than earlier versions. Most failures are due to factors external to the panel.

I can probably give you equivalents if only I could access my frozen PC. In the meantime are you absolutely certain that the diodes have failed by direct testing? Rather than just my suspicion that they have failed, you need to ensure the associated connectors & wiring are satisfactory before. Major generator surgery:-)

First check low power diodes are ok. Check if you have 24v + on F of SK1 with - on W. If no volts there follow tests in ACU4. Unusual to fail unless abused, sounds as if that happened with initial shorting. Make sure of an accurate diagnosis before doing anything!

Will be brief, having to use phone as have pc problems. Charge light is normally activated on it has to be neutralised to off by power from gen. On mk 4 this supply to neutralise the light comes from the low power diode trio in gen. Also supplies regulator module. You may have destroyed dioes. On mk 3 the trio supply the main relay winding unlike the mk 4. Note that neg supply is earthed inside mk 4, in mk 3 neg is only earthed at shunt box. Measure gen output + X -W on SK1.