Ok, I have a voltmeter which I have used to test a few things (battery, alt., and a few switches). Now, my question is: How do I go about trying to track down a short or ground problem? Of course I have no idea where the problem is so I need somewhere to start. I am new at this electrical testing stuff so direct me in layman terms. I have a Haynes manual. I understand resistors, ohms etc. I have been reading about electricity to educate myself. Any assitance would be greatly appreciated, still trying to get back on the road.

Thanks in advance

Anastasia
86' 740 trubo silver wagon

I think the advice on cleaning and tightening grounds is right on. I'll try to get you started on learning to use your meter to check for shorts and grounds.

1. First, remember never to try to measure resistance (ohms) with the power on. This will damage the meter. To be safe, you can disconnect the positive battery cable.
2. Use the meter set to measure X1 resistance. You should have an instruction manual with the meter.
3. The resistance from the chassis to the wire going to the chassis should be close to zero ohms. In a car, the chassis is called the ground. I usually find that ground connections measure 1 or 2 ohms because the test leads themselves don't make perfect contact. If you measure higher resistance than this, remove the wire from the chassis, scrape the connecting area on both the wire and the chassis and reconnect the wire tightly. I use a little silicone grease such as Sylglide on the connection to prevent corrosion. There are numerous ground connections in the Volvo. I would start by finding these, testing them, and repairing any bad ones.
4. A short circuit means that there is little or no resistance between two wires which should not connect at all. For example, I just fixed a problem in my old pick up truck which happened when two wires, which were touching, got hot. The heat melted the rubber insulation and the copper conductors inside the wires touched very lightly. The resistance of this short circuit was about 9 ohms and it really messed up the ignition system. Separating the two wires and taping them fixed the short circuit. It took me a day to find that short. Finding a short circuit often means starting with a circuit which shows a short, opening the circuit in the middle to measure which half has the short and then splitting that half and testing, etc. until you locate the spot where the short has happened. Pretty laborious sometimes.
If your Volvo has the wiring harness which deteriorates with age, you may have some shorts inside the harness. The Turbo's heat may make this worse. If that is the case, you may need to replace the whole harness. Try looking in the 700'900 FAQ for help on this.
'Hope this is helpful, good luck!

What simptoms are you experiencing; blown fuses, intermittant funtions...?

No blown fuses or relays, Battery fine, alt. fine. but still have a charging problem somewhere or a short perhaps.
It all started out as a strange electrical problem. Stepped on breaks, radio cut out. Turned on lights, radio cut out, or just driving down the road with the ignition key in a dead spot (radio off) and my radio would make its beeping sound as though I had shut the car off. Replaced electricial part of ignition switch, and voltage regulator, taped up some wires, car ran great for two weeks. Let it sit for a week, now problem is worse. Car starts but accesories don't work.

I can drive it around and sometimes all of a sudden the volt gauge reads normal and everything starts working. Shut off car or just drive for awhile longer, and then I am back to square one again.

Sometimes, I get into my car and the open door beep comes on, overhead lights etc. a few hours later it sounds sick, yet a few hours later then its back to normal.

Hi,

You definitely have a ground problem. Loosen and retighten ground straping areas.

To start, I believe there should be a grounding area on left inside side panel,(will have ignition ECU grounded here) definitely one next to FI ECU on rt side panel. Remove instrument cluster(2 hidden screws behind pop off covers ) follow black wires from cluster.I think there is another ground area next to relay/fuse cluster area. Inside engine compartment- front left side near charcoal cannister, left headlight( this is a high failure area). Firewall ground strap to valve cover.


Measure resistance of ground from battery post to engine block. High resistance indicates corroded ground wire.(may be internal and not visable at ends)

Measure voltage across ground from alternator to block.

Good Luck , Joe

Thank you Joe! Going to work on it tomorrow! Checked two of those grounds already, but I will check them again!