C900 Rotting Wiring Loom - Advice Needed

[TurboBudapest]

Hello Everyone,

I have a 1985 Saab 900 SPG with the typical mid 80s wiring loom rot. It is pretty bad in many places. Of course this is due to the failed experiment of Saab trying to be green by using soya in their wiring loom coating.

Question is, what is the best way to deal with this? Should I purchase the wiring loom from a later car? What are the pros and cons with this? Is there any particular model year which would suit better than others?

I have looked into having a new loom made by a local company, and the issue with this is that they cannot guarantee that the exact same color cable would be used in the replacement (the striped cable is of a particular problem from what I understand). This can lead to issues in trouble shooting electrical problems in the future.

I would prefer not to T5 the car. I know that the car would run better with T5, but at the moment I would like to keep this car tastefully original with limited upgrades.

Thoughts/advice please?

Thanks!

[TurboBudapest]

By the way, I have been doing a little research, and it seems that the 1986 wiring loom is the same as the 1985, but was made of better wiring and did not suffer from the dry rot issue. Can anyone confirm this?

Does anyone have a good wiring loom from a 1986 16V turbo tha they would be willing to sell me?

[Crazyswede]

The 86 is very close to the 85...such that it should work but there is no guarantee that the wires are any better. Many of the 86's suffered from the crumbling wire syndrome as well. Also keep in mind that the 86's are now almost 30 years old and live in a fairly harsh environment.

[TurboBudapest]

Thanks Crazyswede. So what should I do? Take out the loom and look at what's rotten, and just try to replace the rotten sections? Or should I try to have a completely new loom built? What do people normally do when faced with this issue? There must have been close to 150,000 Saab C900s with this issue built....

Thanks again!

[Crazyswede]

Thanks Crazyswede. So what should I do? Take out the loom and look at what's rotten, and just try to replace the rotten sections? Or should I try to have a completely new loom built? What do people normally do when faced with this issue? There must have been close to 150,000 Saab C900s with this issue built....

Thanks again!

I keep a fire extinguisher in the car and pray that every time I drive it wont be the time it bursts into flames

Unfortunately it is a lot of work to change out the harness system in the car. If you were to go that route I would look for the newest 900 turbo harness that you can find and swap the whole thing in. It may for some small changes to your car but gives you the best impact for your effort. You could also convert to T5 which would solve your efi and ignition harness worries and then you could just start rewiring one circuit at a time as needed for the body. Depends on whether this is a daily driver or going to become a restoration project.

[Jordan]

86 is different than 85 in several areas, but not anything that you could not probably adapt to.

[DeLorean]

If you don't want to re-wire the whole car or go the trionic route, you got to keep the 85 harness (there ARE differences in the harness between 85's and everything else). The starter wire, and the power, and where the 2 big plugs with the 6 wires in them are all run differently in 85's - they even go into the car on the opposite side of the engine bay - this is far from a "direct swap"

I have had luck with some cars removing and dissecting the harnesses and repairing the affected wires. Typically it's the light colored wires, and a whole bunch of the ends (some pigtails from later harnesses may be needed) - but even a pretty bad 85 harness can typically be fixed, only replacing maybe 10% of the wiring.

[Cark]

In my experience it's mostly just the wiring under the hood and exposed to the high temps that suffers from the faulty insulation. I haven't found any issues with any of the wiring elsewhere in the car. It should be said I haven't done a ton of digging around other than the engine bay either... Fortunately I haven't had reason to! As crazyswede jokes about a fire extinguisher, I was shocked my car never caught on fire when I saw just how bad the harness was!

[Geoff]

Between myself, my dad, and my brother we've owned 3 '85 turbos and an '85 8 valve non-turbo. The turbos were much worse than the non-turbo. I re-ran and spliced in a few wires but I also coated some of the wires with plasti-dip (using a small brush) and put them back into the harness. They now make liquid electrical tape so that could be another option. Plasti-dip and liquid electrical tape are ugly though so you want to only do it where it's hidden. You can do some color-coding since they're available in different colors (Plasti-dip at least).

I had two '86 900S cars, neither had any wiring rot problems. Just my experience though.

[DrewP]

I've got 2 '85 16V turbos and they both have had the harness issues, almost isolated to the Jetronic harness in the engine bay (which will come out all in one piece and you can open it up and repair that's damaged) and in the driver's door jam, where those large grey 6-pin connectors are. Those are a pain to get to, but not all that bad. Most other places in the car don't have nearly the issue that the wiring has where it's exposed to heat like others have said.

It's really not too bad of a repair job, can easily be done in a weekend to tackle the engine harness and the door connectors if yours are coming apart.

[TurboBudapest]

Thanks everyone - this has been incredibly helpful. So I suppose the consensus is (i) the damage should be isolated to the engine bay and the driver's door and (ii) best is to try to fix what is there rather than replace with a later model harness and (iii) the Jetronic harness can be removed and rebuilt if needed.

Drew - the cables on the driver's side going through the door jam are completely rotted - I can see it through the whole when the door is open, and just assumed that the rot was everywhere.

Thanks again to everyone!

[Jon1]

This photo is from an 85 spg

The owner abandoned the car at my place. It has been sandblasted and is going to be used to re-shell an 89 spg.
I have two 85 SPGs, an 85 turbo 4-door and two 86 SPGs, all have issues with the wiring.

[SwedeSport]

I found that the easiest way to replace the interior portion of the harness, is to take the whole dash beam off the car and swap the dash beam from the donor car.

Leave all the components attached and just swap em.

I believe the factory assembled the dash beam, including the wiring, then stuck it in the car as a sub assembly.

[Jon1]

I found that the easiest way to replace the interior portion of the harness, is to take the whole dash beam off the car and swap the dash beam from the donor car.

Jason, I have never found any bad wiring inside the car, just the engine bay and doors.

[SwedeSport]

I found that the easiest way to replace the interior portion of the harness, is to take the whole dash beam off the car and swap the dash beam from the donor car.

Jason, I have never found any bad wiring inside the car, just the engine bay and doors.

I parted one with the crumbling harness inside, It was mostly in the floor near the shifter. Probably from the exhaust heat, aka bad heat shield.