Chevrolet 10 Series 1970, Service Manual

Page: 405 / 671

ENGINE-ELECTRICAL 6Y-13
Figo 9c —In itia I F ie ld E x c ita tio n C ir c u it Tests
R esistan ce T e s t). A m m e te r m odels the in itial fie ld
excitation w ire to " A C C ” term in al is open.
5. Switch o ff - p o sitive diode shorted (See Diode T e s t).
Field Circuit Resistance W ire Checks
The resistan ce w ire is an in tegra l part o f the ignition
h arness. H ow ever, the resista n ce w ire is not solderable;
it must be spliced with a crim p -ty p e connector. It is
rated at 10 ohms, 6.25 watts minimum.
The check fo r an open r e s is to r o r fie ld excitation w ire
(connected to the ignition switch " A C C " term in a l) is as
fo llo w s:
1. Connect a test lamp fro m the w irin g harness con­
n ector term in al " 4 " to ground as shown in Figu re
9c (Step 1).
2. Turn the ignition sw itch to the " O N " position and
note test bulb.
a. T e s t lamp glow s - resistan ce is O.K.
b. T e s t lamp does not glow - the re s is to r is open
circu ited - note a lso that dash lamp does not
glow during this test because s e r ie s resistan ce
o f the 2 bulbs causes am perage to be too low.
Field Relay Checks and Adjustment
T o check fo r a faulty re la y proceed as follow s:
1. Connect a v o ltm e te r into the system at the regu lator
No. 2 term in al to ground (fig . 11c).
2. Operate the engine at fast idle (1500 to 2000 rpm )
and ob serve vo ltm e te r reading.
3. If vo ltm e te r shows z e r o voltage at regu la tor, check
circu it between No. 2 term inal on regu lator to " R "
term in al on D elcotron.
4. If voltage at regu la tor exceeds closin g voltage sp e c i­
fication and ligh t rem ain s on, regu lator fie ld re la y
is faulty (R e fe r to sp ecifica tion s). Check and adjust
regu lator as follow s:
Closing V o lta g e Adjustm ent
1. Make connections as shown in Figu re 11c using a
50 ohm v a ria b le r e s is to r .
NOTE: T h is g iv e s us a v a ria b le resistan ce in
s e r ie s fro m a hot lead to the re la y co il.
2. Turn re s is to r to " o p e n " position.
CHEVROLET TRUCK SERVICE MANUAL