Quote:
Originally Posted by CW4B
I also ohmed between the connections on the new ignition switch and compared it to the same measurements (OPEN/CLOSED) on the old ignition switch in two ways with the following anomolies (difference between the switches).
Bottom Line: Vettevet was correct, the old switch was shorting BATT to SOL while switch was in RUN. This caused the starter solenoid to stay energized after engine start, which caused the unpleasant screeching noise after start. Also, I believe, that the old ignition switch connector and purple SOL wire and the next door neighbor ACC wire overheated and melted when I inadvertently left the ignition switch in the run position too long when I was trouble shooting.
TEST: Ground (switch chassis) to G1stayed OPEN in the START position. Not cause of issue though and not a problem given that I don't have a temperature warning light in the dash.
TEST: BATT to SOL was CLOSED (connected) in the ACCESSORY and RUN positions, which is wrong. Should be no power to SOL during ACCESSORY or RUN ignition switch positions. This means that starter solenoid had power when ignition switch was in ACCESSORY, RUN and START positions and the circuit is neither designed to handle that much amperage continuously or keep the starter solenoid engaged all of the time, which caused the purple SOL wire to get scorching hot and melt the ignition switch connector and the adjacent brown and brown with white stripe accessory wires and of course the starter to stay engaged the whole while.
Sorry for the overly detailed explanation, but it helps me work things out. I don't want to burn up the new parts.
Speaking of being concerned about the new parts just getting burned up again, in a previous post, I documented the ohm measurements I took of the wires that go into the ignition switch. Was trying to determine if any of them were shorted to ground or to each other. Some of the measurements were lower than I expected, meaning I was expecting infinity or 0.L meter reading and instead saw readings of 125 ohm or 6K ohms. If anyone can take a look at the measurements I documented in the other post and let me know if i should be concerned, please do and thanks!
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I'm your Huckleberry.
CONDITIONS
Battery disconnected
Starter disconnected
Ignition Switch disconnected
KEY
SOL=Purple to starter S
Check
G2=2 brown wires for brake warn light
Check
IGN=Pink to power HEI
The pink wire runs to a tee and powers the Ignition, The key on fuse panel circuits, and from there to the dash cluster for power to the fuel and temp gauges.
ACC=1 brown + 1 brown with white stripe to accessory on fuse box.
The large 12 gauge brown wire is the accessory wire to the fuse panel but the smaller brown /white stripe wire is the alternator exciter wire that runs to the firewall block on the inside of the cab and from there on the other side it becomes the 16 gauge brown wire to the external voltage regulator. The smaller brown/white stripe is a special wire that incorporates a resistor valued at 10 ohms to match the 10 ohms for the light cluster. It was used by the factory to failsafe the alternator in case the idiot light bulb blew. They just kept it for the trucks that had the gauge dashes without the charging light.
BATT=Red wire to battery (not sure if this actually goes to battery)
This wire runs from the ignition switch to a tee with three other red wires that feed the fuse panel for key off power, the headlight switch, the horn relay, and the main one which goes through the firewall block to the main soldered junction with the alternator, battery, and regulator wires. Actually the flow is reversed from the battery and alternator soldered junction into the cab.so indirectly it goes to the battery
CHASSIS GROUND=not a wire but chassis ground
Check
MEASURES
Are these measures just on the key switch or the wires in the key switch plug.? If just the key switch to ground I don't think there should be any resistance between any terminals and ground with the key off.
CHASSIS GROUND-SOL=infinity
check
CHASSIS GROUND-G2=127 ohm
I'm pretty sure this won't hurt but when key is turned to SOL it should be near zero ohms to gnd. It grounds the brake warning light during start to check the bulb. The other green wires in my picture do the same thing but for the temperature light in the light dashes.
CHASSIS GROUND-IGN=122 ohm I would not like any reading here, this should not be any connection to ground with key on or off. If the harness plug was plugged into the key switch and the key was on, you might see some resistance to ground through the ignition coil.
CHASSIS GROUND-ACC=6K ohm
This is enough to prevent a short to ground but infinity would be better.
CHASSIS GROUND-BATT=7.6M ohm
same here, This is almost infinity
Are these on the harness plug wires or between the key switch terminals? I'm assuming it's between the key switch terminals.
SOL-ALL=infinity
With key off or not in start position, yes
G2-IGN=12 ohm
If this is the brake warning light terminal there should be infinity otherwise the ignition would be grounded and the battery and accessory wire would be grounded when the key was in run or start
G2-ACC=6K ohm
I am not comfortable with this even tho it's a lot of resistance I think it should be more. Check it with the key in SOL(start) you should get near zero ohms.
G2-BATT=infinity
Yes, the BATT wire is 12 volts hot all the time and should not be closed to G-2 with any resistance. Remember G-2 is connected to gnd when the key is in SOL
IGN-ACC=6K ohm That's enough to keep the battery from draining but it should be near zero with the key in run.
IGN-BATT=infinity
key off yes, key on near zero
ACC-BATT=infinity
Same
Should I be concerned about any of these readings?
I think I misread your post and you were talking about the wires in the ignition switch plug so I'll comment on them.
MEASURES
CHASSIS GROUND-SOL=infinity
Check
CHASSIS GROUND-G2=127 ohm
check
CHASSIS GROUND-IGN=122 ohm
I believe this reading is OK because you are reading the wiring resistance through the light to ground.
CHASSIS GROUND-ACC=6K ohm
This is OK as well because all the resistance to loads are switched, If the switches are off you have no path to ground. Try turning on the wiper switch, and the heater switch and then the turn signal switch and watch the resistance decrease.
CHASSIS GROUND-BATT=7.6M ohm
This is OK because 12 volts would not push through this much resistance unless it was in the milliohms scale.
SOL-ALL=infinity
no connection to any of the other wires but you might see some to ground, reading through the solenoid windings, I'd guess near 200 ohms
G2-IGN=12 ohm
This is about right, remember the pink wire feeds the cluster panel and posers the brake warning light so you're reading the light bulb resistance between the pink and brown G-2 wires wires
G2-ACC=6K ohm
Yeah no connection between the BW light and the accessory until the key switch is in run and then the light is not grounded unless the BW switch is grounded or the key is turned to SOL.
G2-BATT=infinity
Pretty much the same as G-2 to ACC.
IGN-ACC=6K ohm
Reading through the fuse panel and cluster feed circuits but not enough to hurt anything .
IGN-BATT=infinity
None here is good no battery drain unless the key is on or in ACC
ACC-BATT=infinity
Sameo sameo
Should I be concerned about any of these readings?
I don't think so but proceed with caution.
leave your battery disconnected until you have all the wiring connected and the key switch is off. Then test the battery for current flow by tapping the terminal to the negative post and look for any spark. or test for a key off drain. If you get less than 50 milliohms between the negative terminal and the negative battery cable, you don't have a short in the key off circuits. You will get more than that if you have any lights or switches turned on so be sure every thing is off.
With the key on and the negative battery cable disconnected, tap the cable on the battery and you will see some spark but not much if all the switches are off , and the doors are closed, radio is off etc.
You can't use the multimeter because it's amps reading is limited to 10 amps and you might exceed that and harm the meter.
Most everything else is fused so if any shorts to ground it will blow fuses.
That's about all I got!