Land Rover FFR Generator panel battery relay

Hi all,

I've been going through the 'all charged up' PDFs, which are EXCELLENT... whilst trying to diagnose a problem with my Land Rover's electrics, with a MK 4 generator panel, the transistorised one. There is the full 28.x volts all the way up to the battery relay, including on the big 'L' shaped piece of steel that forms the bulk of the relay.

The two charging contacts were found quite burnt, especially the vehicle battery one (hiding under the relay), but I have resolved this and some emery and a little adjustment.

The problem is the relay doesn't seem to fire properly, it is intermittent in closing the contacts for the vehicle battery, but also the radio battery wiring. Sometimes it is all fine for a while, but then I see the volt meter dropping away and then the relay contacts are wide open and I am doing at battery voltage. I can manually close it and it works fine, and stays closed for a good while, but it is in no way reliable like this(!)

Now, running through the All charged up PDF, I find one test on page 57 which talks of T1-T5 all reading 28.xV when the relay is closed. However looking at the diagram I can't see how this is the case.... so it has confused me The relay winding (T3) which is 100 Ohm wired in series with the 100 Ohm resistor should mean the voltage would be around 14V, using very simple electrical equations I do actually get 14.xV here, so it ties up with my theory, but not the bible on the subject, which makes me doubt myself Any thoughts?

Secondly, when I do get this 14.xV on T3, it doesn't appear enough to energise the battery relay, however if I touch 28V to T3 the relay shuts smartly and the vehicles electrics are once again working properly.

Battery relay winding tests as 100 Ohm.

So I guess it boils down to whether the jury think the battery relay is dead, dying or there is another problem?

All help gratefully received, hope I have explained things properly

Many thanks,

Pete.

Pete I can't fault your logic. I'm afraid there is a problem with the circuit diagram :red:

I have never found an EMER with the Technical Description of the transistorised panel although the circuit diagram appears in the later Series III User Handbooks.

However there is what purports to be a Technical Description in FAESP 2320-D-100-302 Supplement Annex A. It is very brief & drifts between the transistorised & non-transistorised versions it describes the Test Points as I have depicted but gives very little guidance about their use. This is the circuit diagram which I have tried to translate into a more friendly format.

Therein lies the problem! I should checked against the wiring itself. If you look at the swamp resistor in your panel you will see one end goes to the diode trio & the other to C of PL2 & the choke.

It's taken a bit of time to get my head into this as much of it was written over 10 years ago. But sorry that diagram does need correcting, a revision is due soon as I have some bits & pieces to add but been saving them up.

So on a practical note when you rev the voltage from the generator output should match the vehicle battery voltage creating a balance so that the ignition light goes out. Do it do this completely? As the relay supply comes from the auxiliary diodes, not the main diodes these may be causing trouble. In fact they were upgraded twice on the Mk 3.

If you using are using a Gen No.10 Mk 2 or earlier then your auxiliary diodes are not rated high enough for the transistorised regulator & even an early Mk 3 may be failing. Can you post a picture of your heatsink assembly with the diodes?

Thanks very much Clive, so pleased you turned up to answer, and no need to apologise at all! Your documents are excellent in every way

I've got the panel out and the relay side of the panel disassembled at the moment, but I can confirm the charge lamp does indeed go out once the engine is running, and the voltage rises smartly to 28.x volts.

I'm now not so sure about the diagram being wrong however(!) So you may have been right all along Looking at the swamp resistor leads, they still have the rubber insulating boots on them, and clearly marked with 'T2' and 'T6', which in my mind matches the wiring diagram -would you agree?

This photo also seems to show that this is the case:

http://smg.photobucket.com/user/fv1620/media/Rover/Dsc00893a.jpg.html

I found this a little clearer than the one in the PDF, probably due to file size/compression by Adobe! Pretty sure you can see the two yellow wires going to T2 and T6 though...

If this is correct then it seems that the coil on the battery relay is designed to work at 14V, otherwise I can't see how it would ever work....?

It does seem that I may have a mismatched generator, which is hardly ideal, I have had this truck for many years and not noticed(!) It has charged reasonably reliably to date, and only ever caused problems when it has been left not running for a long period. The generator is plated as No.10 MK2, and I have a No. 9 MK4 panel.

Here's some photos:

A few years ago I did check out all the diodes as best I could, and they seemed to be OK, so would be surprised if anything had failed, but of course I would bow to your superior wisdom here!

One other thing you may notice, is the choke appears to be a bit darker than it should be, it measures as 0.6 Ohms, which I think is probably OK, even so I can't see it affecting the operation of the system too much, or...?

Hope the above makes sense and it not to scrappy, thanks for your help with this!

Cheers,

Pete.

Pete I'm not happy with the diagram around C & E & how it relates to the relay supply. I need to take that board out & look underneath to feel confident about what's happening, but as you know that is pain. Trouble is I'm pressed for time with impending house sale & all that follows from that.

I don't have a 90A system myself this has all been from fault finding on other people's systems. Although I do have a Mk 4 Panel to poke around with (& a spare regulator module)

Using a Gen Mk 2 is theoretically pushing your luck with the auxiliary diodes, they were originally rated to just supply the battery relay, but on the Gen Panel Mk 4 it also has to drive the regulator module as well. But if they failed or gave insufficient output on a set up intended for Mk 4 panel the charge warning light would come on. Whereas the earlier system the charge warning light is driven down by the output from the main diodes.

Thanks very much Clive, appreciate moving house is more of a priority than tinkering with a LR electrics, much less for someone else!

Seems I have been fortunate with the smaller diodes... this hasn't been changed out at any point to my knowledge, so wonder how the mismatch occurred.

The relay board underneath is really very simple:

The thick blue wire is the feed from the battery relay radio batteries output over to terminal T1, I guess it is designed this way due to space constraints around the relay. The metal plate on the bottom LH corner of the picture, with a large blob of solder on, connects the ground terminal for the relay coil, next to T3, to the case, for a good ground, this was checked and definitely making connection.

The board itself is 2-layer, but I can't see any tracks within it, and it makes no sense that there should be, given the diagrams.

Hope that helps a little?

Cheers,

Pete.

Well, to tie this one off in the end, I decided given I have mismatched units, that repairing it, only for it to fail potentially in the future due to overloading the low power diodes, would be somewhat foolish, and just be something to worry about too much in the future

SO.... A plan was hatched, it involved 2*24V 100A relays, and one 24V 10A relay, and a bit of surgery on the board....

I figured that if the low power diodes didn't like switching the later relay, that trying to switch 2 100A relays directly probably wouldn't be too sensible. So, I only use the low power output to switch the small, 20A relay, current draw on this is likely to be less than 100mA, so nothing to worry about in my book. The 'power in' to this relay is taken from the high power generator output, and the 'power out' feeds into the two 100A relays coils, the other terminals of which are of course grounded.

The 100A relays are fed by 2 bolted in bars (M6 studs), and the output goes to the jumper wire which leads to T1, and the vehicle batteries output, which both needed opening out a smidge, again to M6. The diode wires for these two terminals were re-crimped with suitable ring terminals and put in place.

There was however a problem, T6 is fed from T2, via a 100 Ohm resistor, as discussed above, and leaving it in circuit for the small relay would mean I ended up with exactly the same problem, the relay not firing! So... I cut the bent plate/diode mount into two, between the first and second diode, ground it thinner, and turned it around, then connected T2 to this new terminal with a simple jumper wire with two ring terminals on it, omitting the resistor. The resistor still went to the 'other' T6 terminal, so that circuit remains identical. The reason for this malarky is to ensure the polarity protection remains in place.

People may wonder why two 100A relays.... well firstly, that is how the BCK108 does it, there are two sets of contacts, and they are not joined unless the engine is running (charge light out). Otherwise you could flatten both the radio batteries and the vehicle batteries meaning you couldn't escape when being shot at! Also, you have to design it with the POTENTIAL for one of the circuits drawing all 90A from the generator, hence 2*100A relays, and not 2*50A.

I've attached a VERY rough sketch of what I did, modified from your diagram, Clive.

It was a tight fit with everything in there, I ended up removing the mounting tabs from the relays, then remove the case from the relays, bolt this through the board, and then refit the relay innards to the empty boxes.

This may be useful for someone else, I don't believe it a hack, if I had a photo I would post it, but someone buttoned it all up forgetting to take a photo(!) It certainly works, 28.3V at the dashboard, and the same at the radio battery terminals, around 2 seconds after starting.

Thanks for your help, feel free to steal the circuitry if you feel valuable.

Pete well done on giving it thought & evolving a plan that works for you. I quite understand your reasoning for the double relay. Bear in mind the original relay would only draw a few hundred mils, the main current drain is not the relay but the drive for the regulator module that earlier generators aren't intended to drive.

Although I'm fairly confident I have translated the original diagram correctly, I can't help but feel there is an error in the original. But I have not had time to work through it. I do have a Mk4 panel & want to power it up with my 0-30v 10A supply & see just what sort of voltage will work the relay at the same time measuring the current drawn to drive the regulator module.

My present preoccupation is final tweaking of a 5-year project on the Rover screened ignition system which will be a companion to ACU! Soon to be released on here

I've gone through the wiring at that end of the panel & it seems to be correct.

I applied an increasing voltage through F & W (SK1) & the relay consistently pulled at 19v & released on 15v.

Then I increased it to 28v & measured the voltage drop across the 100 ohm resistor as 14v which seems about right.

Maybe your pull-in problems were that the relay tension screw was set too deep?

PS So sorry it looks as if T3 should read 14v

I have just done some measurements to assess the current drawn through the auxiliary diodes.

To simulate the field winding I put a high wattage 15 ohm resistor across V & U.

To simulate the main generator output I applied 28.5v to X & W

To simulate the auxiliary diode output I applied 28.5v from another source to F & W.

The current drawn was 1.88A on HIGH & 0.15A on LOW

Without the resistor the current on HIGH fell to 0.15A. Changing it to 10 ohms drew 2.5A on HIGH

So a typical figure might be a 2A demand from the auxiliary diodes. This is shared of course between the three & these DD3026A Lucas diodes are rated 400PIV 2.5A.

So one would have though its not too much of a demand to fulfil. But we know that uprating the diodes was an issue perhaps it was a heat reliability issue that in everyday use isn't going to be a problem. Because I know of many installations that have used the earlier generator with the more demanding regulator, although I don't know how long they lasted.

Incidentally I have dissected a module & having removed the rubber encasement it was disappointing to see that at least one component lead had never been soldered correctly. Solder had been applied but it didn't flow to the component lead although it had been tinned.

Clive,

That is all excellent stuff, and does make sense. The current draw in HIGH from the aux diodes is quite surprising, but I guess this is fairly early electronics, so probably not a terribly efficient regulator. Are they Ge or Si do you know?

So, from both our experiments, it is clear there is an issue with the relay if it does not switch over with ~14.xV on T3, then something is up. I did wonder if my reay had been replaced by an earlier one, that took the full 28V, but it is clearly marked BCK108, which is correct for the age of the panel. I did play with the tension spring arrangement (though it appeared set as factory by the yellow paint), at one point setting it pretty loose, however the problem then was it did not have enough power to make the contacts come apart again, which is probably even worse I'm beginning to understand it may just be a relay failure, for some reason the coil is not up to producing enough magnetism to pull it closed, why, I do not know...

Modifying the circuit to produce 28V for the relay would be possible, but I would suggest just likely to kill the relay even quicker!

It is good that the diodes are likely to be OK in normal use with the later electronic panel, as you say it may be a 100% duty cycle charging 2 banks of batteries and running the radio in the Sahara where issues could occur -and perhaps not being switched down to 'LOW' in this environment!

I have the BCK108 on my desk if you wanted me to do any tests on it, or I can stick it in the post to you if it would help with your investigations.

Thanks again Clive, every day a school day

Cheers,

Pete.

Si I think Pete. The power transistor reads RCA 16236B but that doesn't make much sense. Here is a similar module

and here is a dry joint hidden from scrutiny, rather shoddy workmanship!

Maybe your module has something like that which would explain the earlier intermittentcy?

With your relay out maybe you could jiggle a few resistances in series to see if your pull in & drop out voltages are similar to what I was getting?

That sounds like a plan, I can only get 12.6, 25, 14.3V and 28.6V, I seriously doubt I have suitable resistors with a sufficient power rating lying around, I can only wish I had a variable voltage power supply!

I do know that at 18V it snaps shut, and 14.xV it is trying it's hardest, but not succeeding! The system appears reliable now, not had any failures from the voltage gauge I installed on the dash a few years back, to monitor just this sort of thing, been sitting happily at 28V, so I think the module itself is probably OK -the dissected one looks nasty! Must've been a Friday afternoon unit...

I take it you were able to measure the field diode current via the inline plug?

Cheers,

Pete.

I can only wish I had a variable voltage power supply!

Pete this is what I bought soley for automotive experimentation. It has been very useful, can be set to constant voltage or constant current.

http://www.ebay.co.uk/itm/NEW-REGULATED-DC-POWER-SUPPLY-WITH-VARIABLE-OUTPUT-0-30V-0-10A-MERCURY-650-682-/261737309857?pt=LH_DefaultDomain_3&hash=item3cf0c266a1

PS I used the in-line plug.