RWD - Speedometer problem- fixed!

Volvo RWD 700 Forum

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Speedometer problem- fixed! 700 1990

My wife has been bugging me to get after her speedometer failure in her 1990 745T. This car spent most of last year apart in the yard as it received a new engine. A good running 1993 940T engine and AW71 went into it without much fuss, but did take me about 4x as long as I envisioned.

Anyway, in the last month the speedometer went from "fine" to "occasional" to "All over the place" to "sittin' at Zero".

I suspected all of the issues were at the rear axle and my friends at the dealership agreed that's the place to start.

Got underneath today and found it's pretty hard to unplug the connector at the speed sensor in the rear axle- the panhard rod is in the way. Right, directly, perfectly in the way. So, with the rear wheels on ramps, I removed the bolt for the panhard rod to the axle (17mm + 1/2 in breaker bar). It came right off and pulled the rod down and out of the way.

Now I could see the connector, pretty well covered in grime and old undercoating. It plugs right into the top of the sensor on the back cover of the differential. I could immediately see the problem- one wire broken clean off, and the other missing insulation for about an inch.

I managed to squeeze the lock tab and wiggle out the plug. Tough to get out and tight for space there. Probably a lot more space on a lift, with the rear axle hanging. Also noticed the tab which used to hold this wiring harness has rusted completely off the axle. As well, the bracket for the e-brake cable has gone away... the pin, the triangle, the end of the bracket- all gone.

Well it was clear there was no real way to fix the connector. The copper was rotten and 1 wire broken right off in a connector pin. I cut back a few inches in the harness, found out the wiring is twisted (for noise reduction?) and noted which color wire went to which pin.

I am lucky enough to have a great parts car, a 94 940 NA wagon with a bad motor. A little looking under the hood yielded a similar plug along side the master cylinder. 2 pin female plug. I clipped it off, matched up the wires, spliced them to the 90's harness, and wrapped the new section with electrical tape.

I placed the new harness over the top of the e-brake cables to keep it from hanging down. I swung the panhard rod back into place, bolted it up, and went to work on the next project... while I was under there I realized she badly needed a front muffler, and the axle pipe end of the old muffler broke off in my hand. *Sigh* as a neighbor commented today, there's always something...

The test drive showed a perfectly working speedometer by the way.

--Rob Bareiss, New London, CT
~ 92 244 M47 modified ~ 89 244GLT Turbo Conversion ~ 90 745T Auto ~ And a VW Bus~


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New 2 Speedometer problem- fixed! [700][1990]
posted by  Aye Roll  on Tue Mar 27 15:46 CST 2012 >

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