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Discussion Starter · #1 ·
I have a replacement 8V turbo distributor (rebuilt one too!) that I already had in my bits collection (Bosch one ending in 003), along with a new hall-effect igntion amp module, a hall-effect ignition amp harness salvaged from a 1982 8V turbo car (which has a replacement hall-sensor cable made from high-qual microphone cable that I made myself a few years ago), and that should be about it for parts.

I haven't checked for sure yet, but it looks like the pinout on the 7-pin connector for the reluctor-style electronic ignition is very close to being identical to the pinout for the same connector when used with a hall-effect ignition amp module.

The transition between point (kettering), 1st-gen electronic (reluctor) and 2nd-gen (hall-effect) ignition systems seems to have varied with the target country that C900's were produced for, and some countries apparently didn't get all three versions during the time classic 900's were imported.

So I'm not sure if anyone in the US or Canada has ever dealt with points ignition (which my 83 900S had) on a classic 900, but fortunately I don't have any cars with that now. :cool:

Who else has converted an 8V car from reluctor style to hall-effect style ignition? The reluctor ignition amp boxes are hard to find and impossible to get new. I don't have a spare for the one in my car, yet the hall-effect modules are easy to get as new parts.

Craig.
 

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Discussion Starter · #3 ·
have you a pic of this reluctor, as might have one
It's a big square black box with aluminium mounting fingers on the LHS and RHS. About 3.5" x 4" square. Here's the one in my car at present (relocated since the engine oil cooler is now mounted where the ignition box originally sat):



flickr page

I've seen one Ebay listing for a used one and never ever come across a new one. I'm sure Saab was not the only car maker to have used the reluctor-style of electronic ignition.

Replacing the setup with hall-effect should be more robust though I'm open to comments on that aspect. :cool:

The hall effect ignition amp module will be mounted exactly where the reluctor ignition box is now (mounting hole spacing is close enough that it'll be a direct fit) as show on the pic. I'll use some washers under the side closest to the outside of the car since the cast aluminium backing of the hall module won't bend like the flat tabs on the reluctor box.

Craig.
 

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Discussion Starter · #4 ·
I was looking through my collection of spare distributors (amazing what I find!) and in the collection were two Bosch 0 237 026 003 distributors which are specified as being for 1982/3 8V turbo cars with APC. My 81 turbo has no APC so I'm just wanting to make sure that there isn't going to be any problem using the 003 version? The Genuine Saab exchange parts list specifies 0 237 026 004 for 8V turbo non-APC cars. Not sure what the difference is.

One of the -003's is actually a rebuilt unit that hasn't been fitted to a car since being rebuilt.


Craig.
 

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Discussion Starter · #5 ·
Moving along with this, I've worked out that the wiring connections for the reluctor module and the hall-effect module have the same colour coding except the reluctor connector is 6 pin while the hall connector is 7. That's ok as I have the salvaged hall module harness I pulled from the 82 turbo sedan I junked a couple of years ago complete with my home-made hall-sensor cable (made from high-quality dual-core screen microphone cable). The mic cable has it's signal wires insulated in blue and white respectively but that's already hooked up with the special connector to go to the -003 hall distributor I'm going to try out. The Saab spec for that cable (same for the reluctor setup) is small brown and green wires.

The only bit I haven't nutted out yet is that the reluctor module has a second blue wire (smaller than the one that goes to pin 1 of the coil) which, going on the Bentley schemtic, goes to something called an 'engine speed relay'. That is include the hashed section of the schematic that's designated as the lambda control circuitry, which my car doesn't have as it's got no oxygen sensor and no extra relay box.

My hunch is that the smaller blue wire goes nowhere and I can probably ignore it when I start moving wires over to the hall module connector though I might pull up the fuse/relay panel just to make sure it is going nowhere. The hall module uses the same green/white wire for +12 volt power, big blue wire going to pin 1 of the coil, black wire for the ground connection, brown and green wires for the sensor cable (blue and white in my custom-made mic cable setup). I can't figure out if the ingition module is fused anywhere but it looks like from about 1984 and up (when hall-effect completely replaced points and reluctor types) fuse 22 started to be used with the cars that have the blade fuse panels. So it may be a good idea to wire in a seperate fuseholder for the hall module seeing as the 81's didn't have a fuse on the feed to the reluctor module (unelss I'm mis-reading the schematic!).

The car does have one custom-mod which is a switch installed in the green/white +12v power wire to the ignition module that the previous owner obviously put in as a manual 'kill switch' for the ignition. The switch is well-hidden inside the car but of course it's a moot point in a 30+ year old Saab however I do use it to disable the ignition as if it's got no +12v volt power the ignition won't operate.

Craig.
 

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Discussion Starter · #6 ·
I think I have worked out the function of the extra relay and the ballast resistor as well. The extra relay is energised off the terminal 50 (cranking) circuit and it feeds power in between the 0.4 and 0.6 ohm individual resistors. The terminal 15 circuit (coming from a distribution block that itself goes back to terminal 15 on the ignition switch) hooks up to the other side of the 0.4 ohm resister and the number 15 wire to terminal 15 on the coil goes to the other side of the 0.6 ohm resistor.

What it seems to be doing is that the extra ignition relay energised off the terminal 50 circuit provides power to the coil during cranking and when the key is let go power direct (unfused!) from the terminal 15 circuit then powers the coil through the combined 1.0 ohm resistance.

What I'm looking to do is pull the extra relay out, and remove the resistor pack then join the wire from the terminal 15 circuit straight to the wire going to the coil.

Bit hesitant to do the actual wiring mods now since I need the car to drive to work tonight, but what the heck I might just go with it and see what happens! :cool: I've got pics of the reluctor connector and hall connector showing the wiring setup in each so if I am forced to put the reluctor system back to use I can without head-scratching about what wire goes where.

I still haven't solved the issue of the small blue wire off the reluctor connector going to a relay that doesn't exist, so for now I'll ignore it.

Craig.
 

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Discussion Starter · #7 · (Edited)
Ok she runs - sort of! No tach signal

Ok she runs - sort of... Until I let go of the key. And the culprit is.... No tach signal to keep the fuel pump relay engaged! Dead giveaway is the tach gauge doesn't move.

More tracing on the 1981 schemtic shows the second (small) blue wire coming off a seperate pin on the reluctor control module provides the tach signal to the fuel pump relay and the tacho gauge. In cars with hall-effect from the factory the tach signal to the tacho gauge and fuel pump relay comes directly from terminal 1 of the coil.

What I don't know is whether the fuel pump relay in my car (the larger silver can type with a terminal 50 connection from the adjacent socket) takes the same sort of signal as the later cars which have the tach signal straight off the coil (which goes into pin 1 of the hall-effect module).

Apart from that, I'm quite happy that it's going. I haven't done any timing checks (my timing gun is 3 hours and about 200 km south of here!) but I made a very careful mark on the valve cover with the indutive distributor still in place and lined up the hall distributor with that. I think I'll need to fiddle with the distributor a little though the weather has just come over stormy so I'm inside until it's safe again.

If worse comes to worse and I don't feel comfy hooking the coil direct to the small blue wire I can manually jumper the fuel pump to get to/from work. I have my fancy fuel pump switch box that I made quite a few years ago that I could deploy to save me having to open the engine bay and pull a small jumper wire though the small wire is probably the safer option.

When I powered up the car to do final voltage and continuity tests, I measured about 3.2 volts on the small blue wire so I don't know if that tells me anything on it's own. Both the large blue and small blue wires are marked as terminal 16 on the reluctor ignition box and also in the schematic. I don't know if the reluctor box lid can be removed but I might see if it can and look if the two terminals are actuall joined internally.

The hall-effect module I'm using btw is Bosch # 0 227 100 139 with a 7-pin connector. It is mounted to a Saab heatsink plate # 85 74 816 (might be 016). The distributor is the Bosch -003 type. I never could find the -004 type that is meant to be used with non-APC engines.

Craig.
 

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Craig, it is quite possible that the difference would be the vacuum capsule, since a unique feature of the turbo distributors of that vintage are the retard travel of the vacuum capsule. Replacement capsules no longer have this feature.
 

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Discussion Starter · #9 · (Edited)
Craig, it is quite possible that the difference would be the vacuum capsule, since a unique feature of the turbo distributors of that vintage are the retard travel of the vacuum capsule. Replacement capsules no longer have this feature.
You might be right. The -003 distributor is a rebuilt one with a turbo vacuum capsule but I didn't see a part number stamped on the capsule to do any cross-referencing with.

I drove the car to work last night with no problems however it does sound like the engine is slightly pinking so I didn't use the turbo much and will definitely check the timing when I in the same place as my timing gun.

Once I nutted out the wiring issues everything from the electrical side is working well. The main mods I had to do were:

- deal with the different pinout of the reluctor and hall modules and transfer wires as required from the 6 to the 7 pin harness,
- sort out the ballast resistor (it's now removed) and join two wires to give +12v to the coil off the terminal 15 circuit. The wire from the terminal 50 circuit is still there but I am not using it.
- remove the second ignition relay (standard 4 pin type) as it's no longer required and can now be a spare.
- sort out the tach signal wiring. Only thing I had to use was a genuine 3M scotchlock connector but when I get my soldering iron (it's where the timing gun is) I might change it to a proper soldered connection.
- make some new mounting holes for the hall-effect module and blank off the ones I'd made for the reluctor module.
- tidy up all the wiring with plenty of elec tape and some split loom tube.
- electrical checks for continuity and voltages in the right places.

I discovered amazingly that Bosch still makes an ignition module for reluctor systems but totally different to the one Saab used - no doubt a more modern version.

I am not sure if the reluctor or hall system is actually better but the hall system is much 'neater' in terms of needing less wiring and 'auxilliary' parts. And it's a good way for me to have learnt more about the car's wiring as the 81 schematics in the Bentley manual are not very clear in some areas so tracing things is 'fun'. :cool:

Dunno about fusing the power to the hall module but I think it needs one as a safety. Have some nice 4-fuse blade holders so one of them will do.

Craig.
 
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