I will start of saying that I have an 85 vette, recently I found out the alternator was dead and after putting in a new one everything seemed to look fine. Voltmeters showed the battery holding at 13.4-7 with the accessories on and 12.4-7 with everything off, I believe that was the normal range. The dash is reading a totally different number, the dash is only reading it at 10.5-11.5v and as a result the car starts rough and sounds like its gonna die, again the voltmeter on the battery and alternator were giving totally different numbers. I went out on a drive to have an auto parts store test the charging system just to make sure it was reading right, the bumpy ride on the highway started to go in the other direction. The volt gauge started to drop, 10v.... 9v.... 8v....7.5v where the car died as soon as it came to an idle/stop. After towing it and putting it back in the driveway I tested the battery terminals again, initially I got a 6v reading and right away figured it was the battery now and all will be fine. After removing the battery I again tested the terminals and sure enough it was reading at a 10.6-11v. Obviously not normal but it doubled voltage from just removing it from the car. I'm gonna try replacing the battery leads and hope those work. Can someone tell me where the negative lead will go to? I believe the positive will go to the starter? (correct me if I'm wrong) and then the other question I had was the location of the engine ground. The alternator clip runs under the engine and I lose it so I have no idea how to remove it to double check it. I checked fuses all were well and I'm stuck with no clue right now.

With that said I'm hoping someone has had a similar problem or some other ways to test the charging system.

Also I have some mystery wires coming from the firewall under the master cylinder. I'd gladly try and take pics if someone has an idea what it is, there's a thick wire coming out of the firewall (perhaps a battery lead? if not thats how thick the wire is) and there's 3 small wires coming out with heat sink around what looks to be a little plug. I don't know, just noticed it when I was cleaning up a ground wire in the area.

But anyways I hope to get some ideas, thanks all
Jason

 

The dash voltmeter reads low if the alternator is not properly charging the battery. Your test voltmeter is reliable. Car batteries are considered discharged at 12.0 volts and below. 12.9 v and above, fully charged and linear in between. Engine running and cold, normal dash voltmeter reads 14.3 volts and 13.3 volts as the engine (and alternator) get up to operating temp. If the battery voltage is too low or too high, the red battery symbol light on the dash will light. You should have seen that when your voltage dropped rapidly. Your battery may be ok, but discharged and I recommend you charge it up overnight with a battery charger. It sounds like your new alternator may not be charging the battery. Engine running, your test voltmeter should read 14.7 volts at the alternator output terminal and the same at the battery terminals. There is a fusible link on the alternator output wire and if you read 14.7 v on the alternator and 12.x volts on the battery, the fusible link is blown and needs to be replaced.
The negative battery cable goes to the frame. below and to the right of the battery. The battery positive cable goes to the starter.

 

I'm not fluent with vehicles when it comes down to electrical, so excuse me if I seem slow :-P, what do you mean fusible link, and how can I remove the output cable to inspect everything, I'm still unsure where that goes (can't seem to find any info on how to remove that).

 

http://members.shaw.ca/agent86/Charging%20System.pdf

 

Fusible links are a splice in a wire with a short piece of wire smaller in diameter which acts like a fuse. It fuses (melts) if the current is excessive and breaks the circuit to save from starting a fire in the car.
What output cable are you talking about?

 

Fusible links are a splice in a wire with a short piece of wire smaller in diameter which acts like a fuse. It fuses (melts) if the current is excessive and breaks the circuit to save from starting a fire in the car.
What output cable are you talking about? It shouldn't yet be necessary for you to remove any wires/cables. Charge your battery up, put it back in the car, start the engine and measure the voltage on the output terminal on the alternator and on the battery just as I recommended. You first need to determine if your new alternator is ok.

 

The battery was reading 12.4-7v and the alternator was around 14.7v, mind you the dash was still giving the low voltage warning. If that means its the fusible link then where can I find that cable to replace it?

I also wanted to thank you for posting that, great file to have around!

 

A shorted diode in your original alternator could have caused the high current that blew the fusible link in the alternator output wire. Your new fusible link should not blow out as the new alternator is working and the battery is supplying normal current to the car right now. Disconnect the negative battery cable when you replace the fusible link on the alternator output wire. On 85's, the alternator output wire goes to the starter.

 

If you have a low battery, and you install a new alternator, the alternator will maybe over current the fusible link trying to bring the battery up to charged status while overheating the fusible link.
Then you change the link, and charge the battery prior to starting the car.

 

The voltage regulator in alternators have a current limit function and the
fusible link exceeds the current limit value.

 

Does anyone by chance have any sort of guide on how to take this wire off? I'm not sure where it runs through and how hard this would be to do myself.

 

Remove the negative battery cable. Cut the old fusible link out of the alternator output wire. Strip each alternator wire and also strip the fusible link wire(should be a short solid #12 wire). Put a piece of heat shrinkable tubing over the alternator wire and the best installation is to solder the fusible link wire to each alternator wire (you can also use an in-line crimp connector) and slide the heat shrinkable tubing over the spliced new fusible link and heat the tubing until it shrinks. Reconnect the negative battery cable. Done!
You can do that I am sure!

 

I feel a little dumb from all of this so sorry if this seems like a stupid question/concern.

I'm still not 100% which wire I should be doing this to, is this the wire that is going to the starter? Is the fusible link on the starter side? I spoke to a guy from NAPA and he said that the fusible link for this is going to be on the starter but probing around down there I'm just not 100% I have the right wire. I just don't wanna be the cause of a new problem :-P

But anyways thanks for the patience and responses and the time you spent making replies.

 

I think I'm gonna end up having to tow this somewhere but I removed the wires and the below is what I found, I am able to use regular crimp connectors for 2 of the wires but theres the one wire with 2 wires coming to it then going down to one solid wire, I can not find a connector small enough for that and even GM dealers have no idea what type of connector this is so finding a replacement to do the same job is out of the question. I got the same response from an electric auto shop. Jfb, as you can see one wire didn't even have a casing and the alternator fusible link is completely gone inside, since 2 were getting replaced we cut the third and will be replacing them all.

 

I don't have an 85 vette, so I can't identify those wires for you. BUT, the largest wire has to be the alternator output wire and I do know that 85's have the alternator output wire go to the starter motor on the same terminal that the large battery positive wire goes to. The alternator output wire should be connected to the positive battery terminal and it should have a fusible link in it. Your picture shows 3 wires with 3 fusible links and all 3 will have to be replaced for at least the reason that their wires were cut right up against the fusible link. You can buy an insulated crimpable connector at auto parts stores, or hardware stores used to connect two wires together, either a butt connection (both wires enter the crimpable conn), or an inline connection (each wire enters opposite ends of the crimpable connector). You will need 2 crimp connectors of the correct size for the wire size on each wire, a total of 6 crimp connectors. You will need 3 fusible links of the correct amp rating. You might consider seeing if the local Chev dealer has replacement fusible links for your 85, or the local auto parts stores. Cut the wires on the other side of the fusible links in your picture, strip the insulation, insert each wire into a crimp connector, insert the appropriate fusible link and crimp. Then use another crimp connector on the other wire of the replacement fusible link and strip the insulation on each of the 3 long wires remaining (these wires went to the fusible links, shown cut right at the fusible link in your pictures, and should be hanging near the starter motor). Insert each long wire into the crimp connector (that also has a fusible link wire) and crimp. That should complete the repair.
If you still have a question, ask away!

 

That arrangement is asking a lot of that ring terminal. That may not be original. I would suggest finding a way of separating the three wires. Perhaps put a ring terminal on each wire, or use some sort of junction block.

 

I have all of the connections but one on the car and they're good to go and I can't find any sort of crimp or clip that will go from 8 gauge to 12 gauge... anyone have some ideas for this? or a good place to look? checked all locale hardware and auto parts stores and nothing and 2 GM dealerships and both are still really unsure why that wire is "there".

Will it be ok if I just solder it together? I think I'm gonna have to just pull the wire out of the protective casing and just solder it.

 

Soldering the wires together is perfectly ok.

 

Ok, I replaced all 3 wires with fusible links and decided to solder them all together, heat sink, taped em up, started up just fine. The car idles at a flat 14v and sounds really strong, turned on all accessories and it went to about 13.7 and stayed at that for a while. After taping them back together and putting them back in the protective tubing I made a promise to myself to never work on electrical connections in my car :-P. Thank you Jfb for all the patience and help, I learned a few things about these cars and at the end of the day no matter how messy things feel and how stupid you feel its great to say I fixed my car myself!

 

Congratulations, you are now an experienced automobile mechanic! ............. and you probably learned some new cuss words too!