Engine: 2.1 Carb B21A: 1983 Estate with electrical problem

[bay_dragon]

This problem started out as me thinking it was the generator so I re-furbished the 55 amp unit in the car. New brushes and re-conditioned copper pads on the rotor. I checked the diodes and did an output test. Works well until I put it in the car. The field winding is sitting at about 1 volt...for awhile. Then it jumps up to 14 or so and the battery starts charging. Along with this problem is the fact that the bottom three fuses in the fuse box have no voltage on them. They're not burnt out they just have no voltage across them to ground. Probably as a result of this, my dash has no power except for the battery charging indicator which lights when the field wire and the generator starts pumping out current. This looks more and more like one of those fatal wiring harness end of life events. My question is... is there a common feed for the bottom three fuses? They are indicated as F14 (Accessory and rear fog lamps) F15 (LH park and tail lamps) F16 (RH park and tail lamps, instrument and panel, light reminder). Going nuts in Volvo land.

[bay_dragon]

I'm going to now assume that this is a wiring problem and I have two questions for the list.
Is it possible to find the plug connectors for the wiring harness from an electrical supply? I don't see my harness listed on any parts suppliers.
Is it fairly easy to replace the ignition harness on these cars without to much trouble?

[Mike_Brace]

I think from meory that fuse 14 is fed from the dipped light circuit. Certainly on UK spec cars fog lights only work on dip beam. Fuses 15 & 16 have a common supply. If you look at the contacts on the fuse box the supply wires go onto the back set of contacts feeding the left hand side of the fuse.
If I remeber correctly fuses 15/16 are fed from the light switch splitting circuits at fuse box so could be a faulty switch - pop switch out and check for voltage in/voltage out.
The lack of dash lights may be an engine earth problem or there may be problems with the loom on the engine - they are known to be biodegrable! The engine loom has a multi-block connection on the bulkhead.
Hope this will get you started on sorting out.
You would find the wiring diagrams in the Green Book invaluable for this.

Mike

[bay_dragon]

Thanks Mike, it did help me get started. I have not been able to find an after market replacement for the engine harness so I've started replacement myself. So far so good. I've ohmed out the wire to the temperature sender, a yellow wire that goes to connection #2 on the plug. The very next wire I tried was the oil pressure sensor which I'm going to assume was a brown wire (tagged SB on the Haynes manual page 303). I traced it down to what I assume was the oil sensor on the front left hand side of the engine (beside the oil filter). The problem is that this sensor has two wires on it. The aforementioned brown wire that goes to the plug and a left hand connection that goes to where I do not know and looks like it might be a green wire? According to the wiring diagram the sensor goes through the idiot light and therefore is not a separate connection. Man these wires are in ROUGH shape making it hard to tell what original colour they were.

[bay_dragon]

Well I finished re-wiring my engine loom and found sadly that it did not fix my gauge problems. I had previously removed my instrument cluster and had checked things out with no luck. Well to make a long story short I eliminated everything up to the dash so was convinced the problem had to be there...I just couldn't detect it. After a long ohmmeter session on the bench I tracked the problem down to the power feed coming into the PCB through the small pin connection. There was NO visual indication that things were amiss however there was no connection from the top of the pin to the PCB. After re-flowing the solder I verified that this was the culprit. Very strangely, the ground connection that feeds my voltage stabilizer does not appear to go anywhere yet the gauges now work!