Re: Alternator Upgrade, Digest #2813

[DeWitt Harrison <de@aztek-eng.com>]

At 05:19 AM 9/28/98 -0700, you wrote:
>DeWitt, again, another superior contribution to the much needed Type 44
survival guide.
Thanks not only for your research and tenacity but your willingness to share
the acquired expertise. 

Ah shucks.

>[ ... ]
>Questions for you: In addition to the passenger footwell splice, tag light
ground, and the intake manifold ground, are there other electrical
connections which have shown to have been problematic and unreliable?  I
don't recall seeing one in the Bentley, has anyone assembled a location
diagram of connections and grounds which we could put on our maintenance
schedule?

I'm not sure I would put electrical connections on a maintenance schedule.
Perhaps it's the sort of
thing to have on a list of things to do while you're in the general  area
for other reasons. Here are a
few items to keep an eye on.

I would clean up the battery negative terminal to chassis connection on
general principle, although
it lives a sheltered life and is probably OK.  I would consider renewing or
replacing the chassis frame
to engine block bonding strap located below the after run cooling blower /
ABS actuator area. It's
exposed to road salts and gets a lot of flexing. After everything is bright,
shiny and tight, spritz a
little battery terminal sealant over the joint to reduce corrosion. The
alternator harness is another
potential trouble spot. I would suggest periodically making some
prophylactic voltage measurements.
On my '88 5kcstq, the main alternator cable runs straight back to the
starter terminal where it is
spliced to the firewall cable. The forward battery access terminal also
joins this circuit at the starter
terminal. This means there are three crimped electrical terminal connections
and two terminal posts
(alternator and starter) in the charging path even before you get to the
dreaded passenger side,
firewall splice. The normal procedure for locating faulty connections is to
measure the voltage drop
across them while carrying a heavy electrical load. Admittedly, access to
test points is awkward on
the alternator harness. If the voltage drop between the alternator output
post and the battery access
post is small, say under 0.05 volts with the cooling fan maxed out, then
most of alternator harness
is good. Then check the drop from the battery access post to the passenger
side butt splice to
check the remaining crimp connection in the forward part of the harness.

>Also, I find that even in cool weather, where A/C is not required, city
driving often keeps the engine coolant temperatures high enough to require
the periodic high-speed cooling fan activation.  Although not a serious
problem, I have decided to install an auxiliary switch in a blank panel spot
to activate the low-speed fan function, same as when the A/C is on, to keep
the coolant temperatures lower and more stable during this kind of driving.
Do you, or anyone, know of a convenient electrical location to tap into this
circuit in the A/C system?

Operating the stage one relay by placing your switch in parallel with the
A/C On signal from the
A/C control head would give you the affect you are looking for. Convenient
location? I doubt it,
but checking the wiring diagram would tell you whether that signal surfaces
out from under the
dash somewhere. Personally, I'm too lazy to be a human thermal switch.

DeWitt Harrison
Boulder, CO
88 5kcstq