insulation to mush?

lmwatbullrun · #1 06-21-2010, 11:45 AM

so, having reasonably well retrieved myself from a silly mistake WRT oil gallery holes and bolts, I fire up the machine (1985 740 TD) and.....all of the warning lights are flickering.

Hmmm, sez I, old wiring. I've been mucking around with the alternator, I probably have a chafed wire or two down there; time for some liquid electrical tape!

An hour later, it is clear that the insulation on the old wires has turned to mush. Literally. Have never seen the like. ALL of them leading from the alternator and the sensor to the blower are mush, and naturally, they are conducting themselves in ways the Volvo engineers never envisioned, I'm sure. No decent engineer would do such a thing. Decorum forbids further description, as this is a public forum.

So, humor aside, does anyone sell new wiring harnesses? If I have this much trouble with the alternator wiring I am sure the rest are decomposing, too.

ngoma · #2 06-21-2010, 10:51 PM

This guy sells harnesses, don't know if he has the one you need:

http://www.davebarton.com/index.html

1985 is one of the years Volvo used substandard engine bay wiring (Bosch); the insulation quickly deteriorates when subject to heat. That is why you will find the insulation totally gone on the wires that run close to the engine, worse where the temp is highest.

If you know how to make corrosion-free crimp connections, it might be most cost-effective to refit those sections that have suffered and leave the rest.

lmwatbullrun · #3 06-22-2010, 01:46 AM

Thanks, Ngoma!

I emailed him and he's going to keep an eye out for me. He does not currently have a harness.

I agree that in the interim I am going to have to replace the wires that are bad. Does anyone have a source for the connectors? In particular, I need the turbo pressure sensor connector and the2 prong alternator connector. Does Volvo still stock just the connectors?

As regards making corrosion resistant connections, I have found that crimping followed by soldering, with a coating of liquid electrical tape topped with heat shrink tubing works reasonably well. Used that for many years for antenna and outdoor RF connections, with success. Is there a technique better than that? I am open to suggestions.

lmwatbullrun · #4 06-27-2010, 03:55 PM

Lucked out; my parts car collection did include a newer engine harness that is not made with bieeuw!degradeable insulation. Took several hours but I got it correctly installed. For reference to those who may have to do the same thing, the RED spade connector goes on the driver side of the stock Bosch alternator; the RED and WHITE spade connector goes on the passenger side. I mention this because the alternator on the car that had the good harness was already gone when I got the car, and the deterioration on the mushy harness was so advanced I could not find a decent piece of insulation to get a color.

Dave does seem to be a decent guy, and I have told him that I want another backup harness whenever he gets one in.

ngoma · #5 06-28-2010, 12:16 AM

Quote:

Originally Posted by lmwatbullrun

As regards making corrosion resistant connections, I have found that crimping followed by soldering, with a coating of liquid electrical tape topped with heat shrink tubing works reasonably well. Used that for many years for antenna and outdoor RF connections, with success. Is there a technique better than that? I am open to suggestions.

Plenty good. Only other thing I can think of is to do the work indoors; less possibility of moisture entering (and becoming trapped in) the connection during the process.