945 charge / earth / warning light prob

[Laird Scooby]

Originally Posted by taiwan740

Check the back of the dash - if the cable has come out then the alternator will not charge. Seriously, it's a total head****.

I had this before when I took the speedo and everything out to give it the hairdryer treatment - when I put it back in, a small cable managed to come out - this was for the battery light. This battery light leads to the D+ terminal on the alternator, and the alternator will not charge without it.

Totally **** and stupid design if you ask me. I took it to a few friends who couldn't spot the issue either, the alternator had continuity with everything, but refused to charge, replaced the alternator, still same thing. Turned out to be that bloody lead.

So yeah, if your battery light bulb is not working or not connected, then your alternator will NOT charge.

Use my test as outlined above and you would have found that before touching the alternator!

[bluebrickrick]

Message received and understood Gents, not sure if those little bulbs have a wattage on them Dave.

Will that also account for the other indicators being out too d'ya think ?

Assuming they are the same I'll change the ignition switch in case it is why the intermittent starter solenoid problem occurs - no way to simulate that one to order.

Cheers for the collective wisdom and moral support

Rick

Edit, just realised I mis read your jumper test - did it linking the alternator stud, not the dash panel wire, will try that first off tomorrow. Also said I'd removed and tested ignition switch when I should have added plug, switch still in situ.

[Laird Scooby]

Originally Posted by bluebrickrick

Message received and understood Gents, not sure if those little bulbs have a wattage on them Dave.

Will that also account for the other indicators being out too d'ya think ?

Assuming they are the same I'll change the ignition switch in case it is why the intermittent starter solenoid problem occurs - no way to simulate that one to order.

Cheers for the collective wisdom and moral support

Rick

Edit, just realised I mis read your jumper test - did it linking the alternator stud, not the dash panel wire, will try that first off tomorrow. Also said I'd removed and tested ignition switch when I should have added plug, switch still in situ.

If the other indicators are out Rick, that points to faulty brushes in the alternator. Volvo were quite clever and the thought has just crossed my mind why the bulb for the charge warning light is the same size/power as the others.

In addition to those warning lights going to their respective switches to bring them on they are linked by diodes to the alternator warning lamp wire so they all come on when the alternator isn't charging. That means there is more than enough current to excite the alternator and start it charging (takes 0.25A in the rotor to start the alternator charging) so if the others aren't on with the key in positoin 2 then there is a fault between the warning lights and the alternator.

Using my jumper wire trick on the warning lamp wire to earth will prove where the fault is - if the warning lights light up, the fault is in the alternator, probably the voltage reg/brushes.

[bluebrickrick]

I thought brushes or slip rings initially Dave but our 240 man from the RAC measured and tried numerous things (including application of the copper end of a Thor to the casing once he had jump started it with his battery pack) but the moment he hot wired the D+ the engine coughed and the driving lights brightened, a few revs to bring the battery up a bit and she ran home on mostly full beam with no problem, re started fine today (I didn't put the charger on overnight as I wanted to see if there was a leak, drain or battery problem)

I've been going through the small print and if the ignition bulb is a different wattage it is not separately specified, I think you are right and it is the same as the others, quite probably for the reasons you suggest.

I have what is laughingly known around the village as the 'Bogside Donkey' a Suffolk Punch mower engine and an old Lucas alternator, on a noce trolley made out of recycled mower wheels, gives me a useful portable 12v power pack for tractor or car starting, LV lighting and powering amateur radio gear (AKA G6IYY but not used it for a while) Went out with this contrivance without its usual small 12v battery so needed to flash it with something, I used a 6 volt lantern battery which worked a treat, subsequently experimented with how little I could get away with and found a half dead AAA cell would suffice to get it away, must remember not to leave connected of course I keep an old cycle dynamo with it now just in case.

At least I have a source of spare bulbs in the donor panel, will drop it in anyway to see if it's speedo is still alive, hopefully two hits in one, fingers x'ed, will let you know.................

[Laird Scooby]

Fingers crossed on the replacement instrument cluster Rick! With the RAC guy hotwiring a second warning lamp into the D+/field terminal of the alternator that proves the brushes etc in it and points towards the existing instrument cluster or wiring in between.

Hopefully it's the cluster and nothing more sinister/tricky to diagnose.

I remember you mentioning the "Bogside Donkey" some time back, in fact i looked into building something similar and in many ways the Suffolk Punch engine was ideal as a vertical engine. However at best it puts out about 3/4bhp from all the research i did on it which is only about 500W,

That's about 35A @ 14V maximum so enough to run some LV lighting or a jump start but not much else. However, for general use as an off-grid power supply, extremely useful.

By the way, a cycle dynamo actually produces ac current so not advisable to use it as an exciter power source for the alternator on the Donkey. Better to use a battery of some description.

[bluebrickrick]

Well, first off I performed the ''Laird Protocol' shunting the D+ lead, no lights resulted on ignition (well just the tank nearly empty and seatbelt ones) so I wrestled out the bezel and instrument panel and systematically checked all the warning light bulbs and holder contacts with the PCB, all clean but guess what the charge bulb was open circuit so heaving a huge sigh of relief replaced it with a working bulb and repeated the Laird protocol to exactly the same result as earlier

I would note for your amusement that my meter battery expired a couple of bulbs into the check so I got out another one, each bulb tested proved dead, as did the new ones, I then realised I had hooked my dead meter black lead onto the PCB while probing with the good meter red ! relocate dead meter to boot and repeat checks - Stupidity, the universes only infinite resource........

Checked the headers and plugs, all clean and no sign of loose wires, ran a lead from the D+ wire at alternator then checked for continuity to the plug at the back of the panel, found continuity to pin 3 from the left (or 2 if counting from 0 instead of 1) on the rh header, this measured onto the PCB as far as a cluster of 3 diodes, have forgotten what I once knew about testing diodes in circuit so more homework later, as a last effort before dark & cold drove me in I tightened up all the PCB screws just in case, mostly checking nothing much to tighten.

So it appears wire from panel header back to alternator intact, no sign of grounding, problem is in the panel

The donor unit is the same spec but having spent an unspecified time unused in a car with windows out I've decided to leave it on the radiator for another night of drying out then clean and resolder all available joints before trying it out.

Can't think of anything else and I'd really like to understand what has happened before swapping panels in case there is a fault on that too.

Rick. older, better informed but by no means wiser

[Laird Scooby]

Originally Posted by bluebrickrick

So it appears wire from panel header back to alternator intact, no sign of grounding, problem is in the panel

The donor unit is the same spec but having spent an unspecified time unused in a car with windows out I've decided to leave it on the radiator for another night of drying out then clean and resolder all available joints before trying it out.

Can't think of anything else and I'd really like to understand what has happened before swapping panels in case there is a fault on that too.

Rick. older, better informed but by no means wiser

The cluster of 3 diodes on the back of the panel Rick, you should find the cathodes are linked together and each anode goes back to the "earthy" side of a different warning light bulb. Have a look at Pg53 (by Doc Viewer #) of this and you'll see how they link up together :

http://www.myvolvolibrary.info/Tech_...ction-3-39.pdf

As such, they're not really "in circuit" so can be tested using the diode test function on your multimeter. On the diagram linked to above, there two lines that link the other warning lights and the alternator warning light are obviously connected in the wiring loom but i seem to recall from the diagram for mine (1988 760 so probably closer to an early 945) that the link of the two wires is on the instrument cluster.

Good call on giving the radiator a chance to dry the replacement cluster out then servicing the joints, i think you may have found the problem!

[bluebrickrick]

That helps Dave, I've been using the '94 Greenbook as closest to 1991 which helpfully doesn't appear to have an equivalent to the P53 diagram of the cluster which you've pointed me at in the '95 version - downloaded it again in case I'd accidentally cut or deleted the page but no missing printed page number in either copy ??

Puzzled but better informed of Bogside about ready for lights out

BTW diagram appears to show a fuse on the cluster 11/41 by A2 on the lhs - any ideas? I looked but didn't notice a fuse or anything blowable nor did I when I had the predecessor apart a few years back chasing speedo gloop damage..........

[Laird Scooby]

Originally Posted by bluebrickrick

That helps Dave, I've been using the '94 Greenbook as closest to 1991 which helpfully doesn't appear to have an equivalent to the P53 diagram of the cluster which you've pointed me at in the '95 version - downloaded it again in case I'd accidentally cut or deleted the page but no missing printed page number in either copy ??

Puzzled but better informed of Bogside about ready for lights out

BTW diagram appears to show a fuse on the cluster 11/41 by A2 on the lhs - any ideas? I looked but didn't notice a fuse or anything blowable nor did I when I had the predecessor apart a few years back chasing speedo gloop damage..........

For some reason Rick, the web version of the 94MY Greenbook seems to be not only missing those pages but is also out of the correct order.

The fuse is cunningly hidden on the PCB and has holes at each end as provision for a repair link to be fitted if it blows.



There it is at the top, on the left. A close up shows the witness marks where i tested the continuity of it :



Cunning fiends, these Japanese!

[bluebrickrick]

Truly, there is no limit to thy Lairdlyness oh Wise One

What is the point of giving a B fuse a B number, missing the page on which it is drawn and then not B marking it ???

Methinks the '94 Greenbook may well have been produced by a close relative of the Muppetts Swedish Chef (or it's a simple scanning oversight by the kind soul who put it at our disposal)

Will update later

Rick the grateful