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Electrical: Engine Starting, Charging
Failing Insulation. [Beth M.] I've had a hot no-crank no-start problem with my
1989 740 GL and had replaced all the usual suspects (RSR, FIR, crank angle/RPM
sensor) and the ignition switch, but still had the problem recurring. Testing showed
large intermittent voltage drops across the positive battery cable, so I decided to
replace the cable. This evening we pulled off the positive and negative cables and
slit the sheath binding the two together. Lo and behold, the insulation on both
cables was worn almost all the way through (to the point that the wiring was
showing in a few spots) and the positive cable had a large crack in the insulation at
the bend. The positive cable also showed signs of wearing through at the point
where the cable comes off the cross member under the A/C compressor. I had
initially intended to only pull the positive cable since it was showing signs of wear
and cracking at the crimps on either end, but now I've got to get a new negative
cable as well. These were most likely the original cables and the car currently has
325,000 miles on it.
I'm just glad that I found this out before I had a car fire.
[Editor's Notes:] See the 960 section for a detailed discussion of
connector repair
Loose Connector Nut. [Klaus Clark] If your positive connector is the same as
mine, there is a smaller wire piggybacked onto the connector. The nut that keeps
the smaller wire on is not the same nut that tightens the cable to the battery. What
feels like a nice snug terminal can have one loose nut. It caused an intermittent
stall during bumps or turns on my 740.
Replacement Harness. [Editor] You can buy a replacement battery wiring harness
from a dealer or from a custom maker such as
Car Battery Failure: Diagnostics.
Service and Diagnostic Tips:
[Motor Magazine, April 2002] The most basic battery services are simple inspection
and cleaning. Following are some fundamental steps:
If the battery has removable cell caps, check the electrolyte level. It should be
above the tops of the plates or at the split-ring indicator in each cell. If
electrolyte is low, add mineral-free drinking water or distilled water. Do not
overfill.
Check battery terminals, cable connectors and metal holddowns for acid
corrosion, and clean as necessary.
Check cables for broken or corroded wire strands, worn insulation and
defective connectors. Replace defective parts.
Look for cracks in the case and loose terminals. Replace a battery with these
defects.
Check the battery tray and holddown parts for looseness, corrosion or other
damage. Clean, tighten or replace parts as needed.
Inspect the battery case and cover for dirt, grease or electrolyte condensation,
and clean as necessary. You can clean a battery with a solution of baking soda
file:///C|/Users/Steve/Documents/Volvo%20FAQ%20Updated/ElectricalStarting.html[01/13/14 10:02:47 PM]
procedures.
battery cable
Custom Battery
Cables.
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