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Electrical: Engine Starting, Charging
had no battery problems for 5 years now.
Cautions:
Don't trust your volt meter in the instrument panel ! Always check voltage at the
alternator & battery. If that alternator is weak you'll notice a drop in fuel economy
because the fuel system tends to go rich as a battery dies. I replace around 40
voltage regulators in a year, and maybe 2 alternators. Be careful of chain repair
operations, gas stations and tow-truck operators: Pep boys technician : "I'll do a
quick battery test." Technician disconnects battery with ignition on and engine at
high idle . Result: INSTANT $865.00 DAMAGE, blowing five relays, radio and other
electrical equip. NEVER disconnect battery with engine running!
Alternator Wiring is Failing. [Editor's Note: See the section on Baked Wiring
Harnesses in Electrical: Circuits, Relays for more information.] One quick thing to
check is the ground wire that goes from the alternator to the engine block. That
broke on me, resulting in my running off the battery with the same symptoms you
have. It was not until I pulled the alternator that I saw the broken wire. Would
have saved a lot of time to check that first. I have been through this on so many
cars that whenever it happens, and the battery proves to hold a charge, I
automatically yank the alternator and head straight for the local rebuilder. I
couldn't tell for sure at first which alternator I had-turned out to be Bosch internal.
I don't remember how much to rebuild, but it was considerably under $100.
[Symptom: idiot lights all go on; also, oil pressure gauge is erratic:] Having all the
idiot lights go on at once is not as strange as it might seem. This will happen if the
small wire leading to the back of the alternator is grounded. It will also happen if
the alternator is not generating any current. When this wire is at ground potential,
it is the same condition as before you start the car - hence the idiot lights are on
so you can check they are not burned out. The wires for the alternator and also the
o/p sender go around the front of the engine under the main crank pulley. (If you
get under the front you will see what I mean.) Dripping crank seals often get oil all
over these wires. Not to mention it is hot by the alternator. Flaky insulation may be
at work. If you really want, you can reroute these wires around the right side of
the car instead and splice into the harness at the firewall.
Alternator Interchange. [Randy Starkie] My experience is that there are three
different alternators used on the 7/9 series cars. The older ones use the Bosch with
the regulator and brush assembly that is also used in the 240's.The two 1994
944Ts we have use the newer Bosch (Denso type) marked as made in Great
Britain- part number 9130275 (shown as superseded by 8111115).The 1992 745
has a small 100 amp Denso alternator part number 3544119 (shown as
superseded by 8251744).The question (finally) is do these units interchange? Is the
mounting hardware similiar enough that if I were to get one of the small 100 amp
Denso and its mounting hardware could I install it on amy of the cars mentioned?
[John Sargent] They all interchange. The later alternators use a larger stud on the
output terminal, and you'll have to carefully ream out the lug on the earlier cars, or
replace the lug. The small Nippondenso unit is supposed to have better voltage
regulation.
file:///C|/Users/Steve/Documents/Volvo%20FAQ%20Updated/ElectricalStarting.html[01/13/14 10:02:47 PM]
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