240 General: 244 - Rev Counter

[Othen]

Hi again,

I'm working my way through lots of little jobs on my 1980 244, the next one on my list is to fix the rev counter.

I'm making sure the external connection is okay first, before I open up the instruments. I've traced what I think is the sender wire from the coil to a place just in front of the driver's side bulkhead. Could anyone tell me what this cylindrical item is:



The red wire from the coil seems to be connected with a orange wire at one end, and the green wire emerges at the other:



I'm guessing it might be a ballast resistor, but without knowing what it is I can't really test it.

Any ideas?

Alan

[Clan]

The Object is the ballast resistor for the coil It should be low ohm value up to 5 ohms perhaps , they are very robust and never go wrong ..

The Tachometer signal wire is Red & White and goes on the coil negative ( Marked 1 ) which will also have a white wire which goes down to the distributor for the contact points .

The coil + terminal will have a brown wire which goes to one side of the ballast resistor and carries on down to the starter ( Terminal 16 if i remember right )
The ignition power feed is the blue wire which goes from the other Ballast resistor terminal to a tag on the fuse box .

The red wire is not part of the volvo loom ... it is something added by someone else !

[Othen]

Originally Posted by Clan

The Object is the ballast resistor for the coil It should be low ohm value up to 5 ohms perhaps , they are very robust and never go wrong ..

The Tachometer signal wire is Red & White and goes on the coil negative ( Marked 1 ) which will also have a white wire which goes down to the distributor for the contact points .

The coil + terminal will have a brown wire which goes to one side of the ballast resistor and carries on down to the starter ( Terminal 16 if i remember right )
The ignition power feed is the blue wire which goes from the other Ballast resistor terminal to a tag on the fuse box .

The red wire is not part of the volvo loom ... it is something added by someone else !

Many thanks - that is really helpful.

I'm guessing the red wire was inserted when a PO changed the distributor to the solid state points type (I think this car would have had CB points when it was made), and changed the coil to an aftermarket one at the same time. I don't know why the red wire would have been required (but this car is 40 years old next month, so lots could have happened in the meantime).

Now I know what is what I can start to eliminate things and get the rev counter fixed.

Best wishes,

Alan

[Clan]

Originally Posted by Othen

Many thanks - that is really helpful.

I'm guessing the red wire was inserted when a PO changed the distributor to the solid state points type (I think this car would have had CB points when it was made), and changed the coil to an aftermarket one at the same time. I don't know why the red wire would have been required (but this car is 40 years old next month, so lots could have happened in the meantime).

Now I know what is what I can start to eliminate things and get the rev counter fixed.

Best wishes,

Alan

I would revert back to standard , the electronic ignition will be your downfall one dark wet night in the mddle of nowhere you don't need it .. The bosch points are faultless when you change them every 6000 mile service .. Get the right volvo coil too as that it very high out put .

[Othen]

Originally Posted by Clan

I would revert back to standard , the electronic ignition will be your downfall one dark wet night in the mddle of nowhere you don't need it .. The bosch points are faultless when you change them every 6000 mile service .. Get the right volvo coil too as that it very high out put .

Thank you, but unfortunately I don't have the original distributor, I'm fairly bound to make the current system work properly (it works fine now, it is just the rev counter that doesn't register).

Best wishes,

Alan

[Othen]

Originally Posted by Clan

The Object is the ballast resistor for the coil It should be low ohm value up to 5 ohms perhaps , they are very robust and never go wrong ..

The Tachometer signal wire is Red & White and goes on the coil negative ( Marked 1 ) which will also have a white wire which goes down to the distributor for the contact points .

The coil + terminal will have a brown wire which goes to one side of the ballast resistor and carries on down to the starter ( Terminal 16 if i remember right )
The ignition power feed is the blue wire which goes from the other Ballast resistor terminal to a tag on the fuse box .

The red wire is not part of the volvo loom ... it is something added by someone else !

Hi Clan,

I wonder whether a PO has fitted an electronic ignition system from a later model 240 - I'm pretty sure my 1980 car would have been fitted with CB points when it was new, but now the distributor looks like this:



... and inside:



... and the ignitor box looks like this:



Regarding the wiring, the red wire to the ballast resistor you spoke of seems to be a direct replacement for the brown wire you mentioned (no sign of it), it runs from one end of the resistor to the +ve side of the coil. As you may see, a black wire also connects to the +ve side and runs to the ignitor box.



The red/white wire (I'm guessing the signal sender for the tacho) is attached to the -ve terminal of the coil, as in your note above, but there is no white wire on that side of the coil (as there are no CB points).

I suspect this is the root of my rev counter not working: not receiving a signal from the CB points. I rather assume the electronic ignition is wired correctly, with the ignitor box connected to the +ve side of the coil, because the car runs fine. Assuming my idea that the system is from a later model of 240, I need a wiring diagram to work out how the signal gets to the tacho via the red/white wire.

Alan

[Othen]

... one of the issues with working on a 40 year old car is that lots of things may have been done to it over the past 40 years - some of them good things, some not so good.

The red/white wire I mentioned in the post above turned out not to be connected to the rev counter when I traced it, but to the ignitor box - which appears to be a later addition replacing the CB system. So, it appeared that there was no sender wire connecting the instrument to the -ve side of the coil, so I started looking around bulkhead and found what appeared to be a red/white wire, not connected to anything (wrapped in some electrician's earth tape):



It looked slightly promising, so I put a bullet connector on the end and ran a wire round to the -ve post of the coil:



It was a long shot but worth a go - unfortunately it has not breathed any life into my tacho. I decided that was enough for today and have retired to have a think about it, the explanations could be:

a. That the red/white wire I found is nor connected to the tacho, but is just another random wire.
b. That it is the correct wire, but there is some other fault further along the line.
c. That the rev counter is kaputt.

I think the only way I'm going to be able to find out is to open the instrument cluster and test for continuity, power and earth return, but that is for another day. The lack of a rev counter is a minor irritation that doesn't detract much from the Royal Barge's good points.

Any ideas?

[Clan]

Originally Posted by Othen

Hi Clan,

I wonder whether a PO has fitted an electronic ignition system from a later model 240 - I'm pretty sure my 1980 car would have been fitted with CB points when it was new, but now the distributor looks like this:



... and inside:



... and the ignitor box looks like this:



Regarding the wiring, the red wire to the ballast resistor you spoke of seems to be a direct replacement for the brown wire you mentioned (no sign of it), it runs from one end of the resistor to the +ve side of the coil. As you may see, a black wire also connects to the +ve side and runs to the ignitor box.



The red/white wire (I'm guessing the signal sender for the tacho) is attached to the -ve terminal of the coil, as in your note above, but there is no white wire on that side of the coil (as there are no CB points).

I suspect this is the root of my rev counter not working: not receiving a signal from the CB points. I rather assume the electronic ignition is wired correctly, with the ignitor box connected to the +ve side of the coil, because the car runs fine. Assuming my idea that the system is from a later model of 240, I need a wiring diagram to work out how the signal gets to the tacho via the red/white wire.

Alan

That distributor is from a volvo 360 GLT the timing advance will be wrong for your engine , I stick with my original recommendation scrap it , find the correct distributor and revert back to standard .. That cap is poor quality too , not up the volvo standard .. it all points to further breakdown and trouble in the future as it is ..

[Othen]

Originally Posted by Clan

That distributor is from a volvo 360 GLT the timing advance will be wrong for your engine , I stick with my original recommendation scrap it , find the correct distributor and revert back to standard .. That cap is poor quality too , not up the volvo standard .. it all points to further breakdown and trouble in the future as it is ..

Hi Clan,
Thank you for that. I'll have to think about reverting to a CB setup, I'm not worried about points per se (one of my older bikes still has a CB arrangement and it works fine), but I'm not sure it fits in with my aim for this car. It is 40 years old and has had a few things done to it over the decades - on the whole (apart from a few atrocities like the roof spoiler that had to go) its evolution is part of its charm.
Many thanks for the good advice about the rev counter sensor - I'm on the right track to solving that piece of the puzzle.
Best wishes,
Alan

[Othen]

To finish this one: it was an easy fix. The black wire connected to the back of the tacho was not connected to anything at the other end, just rolled up and taped over close to the coil. I put a female spade connector on, pushed it onto the coil -ve and it works fine now.



I have no idea why a PO might have disconnected it, and it must have been really irritating.

Alan