1979 C10 temp. gauge and alternator questions.

[Rangerman]

Temp gauge in the dash works good but where does it get its reading from?

Coming out of the intake, theres a wire that runs to a temp gauge that is zip tied onto one of the master cylinder lines?? No idea why its there, but its accurate also.

Fixing to replace the alternator with a 94 amp for a 85 camaro, on the back of the alternator theres the 8 gauge wire and another 16 or 18 gauge wire that goes directly to the battery, should the small jumper wire be there?

This is a nice truck but a D.A. owned it before me.

[hatzie]

Temp gauge sender is in the LH cylinder head.

Got a picture of the extra wire on that 12SI?

[Rangerman]

That yellow wire goes to the battery it's connected to the back of the alternator.

[hatzie]

That's the BAT stud. The output wire is supposed to be there.

Someone did some bubba wiring there. Is this yellow wire on your truck or the donor F-Body?

On the CK trucks the output wire is a red 12ga wire that runs from the BAT stud to a fusible link on the firewall J block for charging the battery.
The red wire on the plug terminal 2 goes to a fusible link on the starter. This is the sense wire that monitors the system voltage to regulate the output voltage.
The brown wire to terminal 1 is a resistance wire around 45-55ohms that goes to the ignition switch on gauge option trucks. On the low option trucks this same wire would have no resistance to the GEN lamp on the dash. This is the ignition/indicator lamp wire. This terminal is a ground till the regulator starts calling for charge then it becomes full system voltage to turn off the warning lamp.

[Rangerman]

This is my sons truck, don't understand f body donor?

[hatzie]

You were talking about using a 94A Delco 12SI from a 1985 Camaro... I assumed it was still in the donor chassis.
F-Body = Firebird-Camaro.

If you're buying a rebuilt alternator a CS130 will give you more amperage.

If you're having charge problems fixing the original alternator circuit is a good place to start.

[Rangerman]

Thanks for the help.
I was going to go to NAPA and get a rebuilt alternator, no problems just getting ready to put a new motor in and was going to go with dual fans on the new radiator. I'm sure this was the cheapest alt the po could use. I'll get the one you recommend.

So just leave the yellow wire where it is?

[hatzie]

This is a snippet of the 1979 wiring diagrams with the alternator and starter hookups.
GM called the alternator a generator in the earlier wiring diagrams. Don't know why.
The big fat wire at the starter is the 2AWG battery + lead.


Decoding the wire labels.
The wire label consists of 4 parts. Wire gauge, color, circuit#, and wire type. In 1979 the wiring diagrams used mm rather than AWG for gauge. There's a conversion table on page 1 of the 1979 wiring diagrams.

The charge wire on the alternator BAT terminal is labeled "3 RED-2C (SXL)"... "12AWG RED Circuit 2C SXL wire". The fusible link at the Junction Block is labeled "1 RED 2F THERMO HW" which means "16AWG RED Circuit 2F Fusible link wire".

Wiring diagrams etc are in the RTFM links in my signature...

[hatzie]

Originally Posted by Rangerman

Thanks for the help.
I was going to go to NAPA and get a rebuilt alternator, no problems just getting ready to put a new motor in and was going to go with dual fans on the new radiator. I'm sure this was the cheapest alt the po could use. I'll get the one you recommend.

So just leave the yellow wire where it is?

The yellow wire is likely not the right gauge with a PVC jacket. The wiring diagrams call for Type SXL (special purpose cross-linked polyethylene) automotive primary wire which is specifically made for use in engine compartments where higher heat resistance is required. PVC jacketed wire will deteriorate fairly quickly in the engine compartment.

I'm not sure what the PO (previous owners) were trying to fix... At a guess the red 12ga charge wire is damaged.
If the red wire from the alternator BAT terminal to the J block on the firewall is damaged I'd fix the red wire and ditch the PO "repair".

[Rangerman]

Damn, thanks again for all the great info.

Im book marking this page for reference, ill use the diagram and figure out what they did.