945 charge / earth / warning light prob

[Laird Scooby]

Originally Posted by bluebrickrick

That is a nice result for just pulling a fuse

the donor has an ABS block which I hadn't intended to remove but can do (assuming it and the trailer are still there!) just in case (and assuming compatible) or are you looking at the speedo sensor which I think I've read co feeds the ABS as there aren't the cogged sensor rings like the front hubs have, I feel your pain brother.

BTW Donor cluster is 1991, the one in it was 1990, noticed a minor difference, the 91 has three diodes behind the tacho, the other had pads for 3 but only the rh two installed - thankyou Swedish Cheff instructing Kamikaze circuit maker

It is indeed, assuming it has a Lambda sensor on it, the ones without don't store fault codes.

Very intriguing fault on mine. To explain it, first a bit of history. In 1988 on the 760, Volvo in their infinite wisdom decided on the back axle, they would fit a 96 tooth reluctor ring for the ABS and 48 tooth rings on the front wheels.

Because the speedo was set up for a 12 tooth ring on the back axle, they hda to fit a speedo converter which divided the frequency by 8, to give the right amoutn of pulses for the speedo.
Therefore for each turn of the wheels, the ABS ECU is expecting to see 96 pulses from the rear sensor and 48 pulses from the front sensors.

However, i had to replace the back axle last year and the replacement is from a later car (96MY i think) with 48 teeth on the reluctor ring so the first thing i noticed was the speedo was reading 30mph at 60mph real speed. The ABS warning light was also on.

I pulled the speedo converter apart, reverse-engineered it and changed the output from every 8th pulse it gave a pulse out to the speedo to every 4th pulse so the speedo now read correctly.
The ABS light was still on though because the ABS ECU was still expecting 96 pulses from the rear for each turn of the wheels and 48 from each of the fronts.

Doing some digging, it transpired that from about 1990 on, they moved to 48 tooth reluctor rings on the back axle. As such, the ABS ECU was changed so once i was able to work out what year ABS ECU i needed, i found one on ebay.

Hoping it would be a plug'n'play job it landed today so i plugged it in. Now, instead of waiting until it's done 200 yards to bring the ABS light on, it comes in within a few feet of moving off suggesting a duff sensor.

After searching intently on the inernet, i eventually uncovered a 1991 740 ABS diagram and it appears i need to move one wire in the connector plug to reconnect said sensor.

Then hopefully it will be all systems go! Weather, health, energy etc permitting tomorrow, i'll move that wire inside the plug and hope!

Thanks for the thought on the ABS block though, much appreciated! Just for fun, from 1992 on, Volvo switched to the Bosch ABS-2E system from the original, major wiring mods to fit an ECU from one of those which i already have as i bought one with the same sort of idea a few months back.

[bluebrickrick]

OK So today was a sliding back down a snake day ! Probably my fault as getting into the car to go shopping I joked with Mrs Bluebrick that I wondered if all would be as last night or if we would be playing spot todays interesting fault instead - well it was the latter

On the way back I stopped to pick up a neighbour about to walk back in the rain, put the headlights on restarting only for the dash to be back in darkness. On getting home I had the cluster out to have a look and just make sure the plugs were all home, ignition on, no warning lights either or charge when started. Made up an alternator shunt not relying on a croc clip so I knew I could get back to pick them up later and investigated the back of the cluster, ignition bulb working and good contact on PCB, then I noticed the fuse on the PCB had blown, ended up with a couple of small self tappers holding the thinnest fuse wire I could find and hey presto warning lights and charging back to normal and return trip with the shoppers uneventful, illuminating lights still firmly out and while I overlooked it initially I did eventually remember the dash dimmer, it wasn't on nil and moving it up and down had no effect. So what pulled enough current to blow the fuse link and why no lights, checked fuse 24 (IIRC) for rh dash lighting etc, radio and pipelighter socket live and fed elsewhere.

Beatings will continue until morale improves..........

PS I'm wondering if they are on the lights at the end of the tunnel circuit and if so, should I be worrying - last time it was just some ba$%ard with a torch and more work!

[Laird Scooby]

Originally Posted by bluebrickrick

OK So today was a sliding back down a snake day ! Probably my fault as getting into the car to go shopping I joked with Mrs Bluebrick that I wondered if all would be as last night or if we would be playing spot todays interesting fault instead - well it was the latter

On the way back I stopped to pick up a neighbour about to walk back in the rain, put the headlights on restarting only for the dash to be back in darkness. On getting home I had the cluster out to have a look and just make sure the plugs were all home, ignition on, no warning lights either or charge when started. Made up an alternator shunt not relying on a croc clip so I knew I could get back to pick them up later and investigated the back of the cluster, ignition bulb working and good contact on PCB, then I noticed the fuse on the PCB had blown, ended up with a couple of small self tappers holding the thinnest fuse wire I could find and hey presto warning lights and charging back to normal and return trip with the shoppers uneventful, illuminating lights still firmly out and while I overlooked it initially I did eventually remember the dash dimmer, it wasn't on nil and moving it up and down had no effect. So what pulled enough current to blow the fuse link and why no lights, checked fuse 24 (IIRC) for rh dash lighting etc, radio and pipelighter socket live and fed elsewhere.

Beatings will continue until morale improves..........

PS I'm wondering if they are on the lights at the end of the tunnel circuit and if so, should I be worrying - last time it was just some ba$%ard with a torch and more work!

Bit of a bummer all that Rick!

Which ignition/starter switch are you running on, the original or the replacement?

Thing is, there's nothing i can think of that pulls any current from the instrument cluster, all the warning lights are earth-switched so wouldn't even matter if one of the wries for those shorted to earth, it would just bring the warning light on.

It could simply be the fuse on the PCB has got old and fancied a break. Yes, that sounds facetious but it's serious, i've known many fuses that have given up the ghost simply through old age. Volvo obviously foresaw this but including the holes for the self-tappers and the implication that a new fusible link could be retro-fitted.

I've also had a head-cabbage day, swapped the wires in the ABS ECU plug, took it for a test drive and just as i was thinking i'd cracked it at the "magic distance" and gone past the point where the ABS light would normally have come on and nothing, just starting to feel smug and on comes the light.

I have a couple of theories, going to try and look at at least one of them tomorrow, weather etc permitting!

[bluebrickrick]

Another day tomorrow Dave, there will be a blindingly simple answer then we can get on with screwing something else up for a while

I'm happier with my more robustly wired get you home linkage tie wrapped to a nearby hose, just a spade to swap over, plus a spare battery in the footwell.

Let you know what Friday brings.

[aardvarkash10]

Took Moomin for a stroll to the beach for the weekend and on the way back...

Note the moonshine limp-home mode.

Beach was nice though.

[Laird Scooby]

Originally Posted by aardvarkash10

Took Moomin for a stroll to the beach for the weekend and on the way back...

Note the moonshine limp-home mode.

Beach was nice though.

Oops! Probably the same problem as Rick had, voltage reg/brushes worn.

[aardvarkash10]

pretty sure Dave, yes. But I'll hoick the alternator out and do bearings etc while its stripped - with my luck if I just drop a new reg and brushbox in, the drive end bearing would seize the next week!

[Laird Scooby]

Originally Posted by aardvarkash10

pretty sure Dave, yes. But I'll hoick the alternator out and do bearings etc while its stripped - with my luck if I just drop a new reg and brushbox in, the drive end bearing would seize the next week!

Sods Law exists globally Ash so a wise move!

[aardvarkash10]

turns out its slip rings, brushes and bearings. The regulator tests ok but I'll throw a new one at it anyway - its done nearly 1/4m kilometres after all...

Moomin back to the land of the correctly charged by end of weekend hopefully.

How are your electro-mechanical ministrations going Rick?

[Laird Scooby]

Par for the course on one of those Ash, almost precitable. Very occasonally the rectifier will fail but usually they're good to go another few years/decades.

Best i ever saw in an alternator was a Hitachi LR160 with stainless slip rings - they will never wear out but the brushes do.