Do I need a 61 amp alternator? - Page 3 - Chevelle Tech
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post #31 of 35 (permalink) Old Sep 2nd, 19, 1:33 PM
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Re: Do I need a 61 amp alternator?

Quote:
Originally Posted by Jim_66SS View Post
Just thinking Al, could there have been a design change where my harness was designed and used either before or after the design seen in the AIM or 66 Chassis service manual?
Anything is possible. But a design change should appear in the AIM or possibly a bulletin which we don't have.

When you look at the GM wiring harness design, you can see a progression from birth that follows through years and models. The 67 wiring harness may give hints in the progression from 66 to 67.

I do have various pictures of horn relay wiring pulled mostly from the net that help prove your assertion of a single wire in the front harness. My guess on this is that these were the cars without an amp gauge. I'll post some up in your other thread, maybe someone will have more info.


Section 3 in this link goes over the method to verify the wire gauge in stranded wire. It involves cutting the wire, measuring a strand and counting strands. A major PITB.

https://www.wikihow.com/Gauge-Wire

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post #32 of 35 (permalink) Old Sep 2nd, 19, 6:11 PM Thread Starter
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Re: Do I need a 61 amp alternator?

I may be wrong here; but when looking at old parts catalogs from october of 66, it looks like the 327 w special high per got one of two engine harnesses depending upon if it came with AC or Not.

One of two engine harness for the 396 depending upon if it came with AC. No mention of gauge package. Obviously there should be one used with the gauge package unless they expect you to do something there on your own.

And again the same case for the 6 cylinder. No mention of any other engine harness for the other V8 options. Odd unless they wanted you to replace with the 396 harness.

Note Jeff Helms has said those books are not always correct regarding factory parts.

Unless someone swiped a different harness into my car, then the 327 I took apart and my SS car used the same front engine harness with the exception of the ammeter wires

AIM says to use 6290304 for 396 engine. And 6290301 for all other V8 engines. These #'s are not mentioned in the parts book. Again no mention of whether or not it has the ammeter gauge and not mention of a special engine harness in the U16 gauge package although there is a diagrams for hooking up some wires at the horn relay, looks like 3 or 4 wires.


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post #33 of 35 (permalink) Old Sep 2nd, 19, 6:17 PM
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Re: Do I need a 61 amp alternator?

Post a picture of the diagrams in the AIM if you can.
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post #34 of 35 (permalink) Old Sep 2nd, 19, 6:51 PM Thread Starter
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Re: Do I need a 61 amp alternator?

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Originally Posted by DUTCH MAX HEADWORK View Post
Post a picture of the diagrams in the AIM if you can.
Sorry I was looking at the wrong diagrams, I was looking at engine harness.

I should have been looking at Generator/lighting harness.


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post #35 of 35 (permalink) Old Sep 3rd, 19, 3:04 AM
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Re: Do I need a 61 amp alternator?

Quote:
Originally Posted by Jim_66SS View Post
Well AL I found something interesting. I remembered I had the front wiring harness out of a Nov of 65 built 66 chevelle with AC from the factory, except it did not have the gauge package. It still have every original connector and the non-sticky tap, grommets, etc. One Red wire (thinking it is 10R) from junction box to the splice for the horn relay, regulator, alternator, and power to fuse panel. And one Red wire (thinking it is 10R) from the horn relay to the splice leading to the horn relay. And one wire (thinking it is 12R from the splice to the alternator Just like what is in my car, except my car looks like the Red wire from the splice to the alternator looks to have been replaced with the same size wire 10R as coming from the junction box to the splice. And I have the wires for the ammeter gauge and this harness does not have those wires.

Maybe the wiring changed sometime before or after when this car or my car was built and the printing of the diagram. My wiring looks suspiciously like the 67 chevelle wiring less a fusible link and a fuse down the line from the split of the 10R from the junction box.
One of your questions earlier was about the shunt. You won't find a physical device in your system that is a shunt. Your shunt is a circuit formed by the way the 10 GA wire that crosses the radiator between the 2 amp gauge wires connected at each end of that line. The reason your gauge shows a high charge with the fan on high is because you are pulling power past this shunt since your a/c is pulling off the battery terminal.

If your harness has the 10 gauge wire currently from the junction block to the horn relay, you're good to go with a 61 amp alt. The 10 ga charge line from the alt to 4way connector is fine. Moving your take-off point for the under-dash a/c relay to the horn relay would get your amp gauge functioning properly. If the only wire you have between the junction block is a 12ga, then you are underwired and at risk.

I did receive your a/c diagrams and you said you hooked it up per the 65 diagram which has a relay. It shows hooking into the starter solenoid and powering through the battery cable. This is not ok because the power to charge the battery and run the a/c will need to flow through the small wire between the batt and rad terminal. If you run that ac supply wire to the rad terminal, then you would be ok, but still have the high reading on your amp gauge.

I can only speculate on the following...The wire between the batt and rad term is intentionally left at a smaller gauge. It's the wire that will smoke and burn should you have a short in the wires to the horn relay. Since it's such a small ga wire, I would replace it with a 10 ga wire to equal the gauge of the wire to your horn relay. I would install a 14ga fusible link in that wire. This main 14 ga fuse link protects the alternator charging line, the wires across the radiator support and the power bussbar at the horn relay.

Hooking up your ac per the 66 instruction would open another chapter of grief. It pulls all power off the ignition circuit which is already tasked with headlight, ignition, and just about every other circuit in the cab. The only good news is your amp gauge would read correctly.

More, by hooking the ac to the 4way connector or horn relay bussbar, your alt sense wire reads from this point and will work to give you proper voltage to the a/c and rest of the system just like the factory had in mind.
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