1985 Southwind Alternator overcharging 15. 8 volts

[ken swick]

My 1985 Southwind 454 Chev engine is overcharging. Checked all grounds and they are clean and tight.
1. Is the volt regulator internal to the alternator? If not, where is it located?
2. Where is the battery isolator located and how do you test it?
3. There is a solenoid looking part attached to a bracket behind the alternator with a thick red battery wire and other thin ones. What is this item?
Any advise will be greatly appreciated ... love the old Southwind, but she does have issues ...

[Skip426]

Sorry your here with problems .
85 GM alternator , most likely internal regulator. But you would need a number off the alternator to confirm.
Every coach manufacturer mounts their electrical components differently, but tracing the heavy wire from the alternator should lead you to it.
Any chance you could post a picture of the part you're trying to ID.
Info on posting photos is in the " FAQ " drop box in the blue bar under your welcome message.
You dual battery isolator may look like the photo below; many manufacturers used these.

[Kurmudgeon]

Your alternator is most likely a Delco 12si, internally regulated. If it's rated output is greater than 94 amps, it would be a 15si or 27si. Have you tested output with a known accurate voltmeter? Dash gauges are not known for their accuracy.

If it is actually putting out too much voltage you have two options:
1) Easy and expensive is to replace the alternator.
2) A little more difficult and far cheaper is to replace the voltage regulator. If you have the mechanical skills to disassemble and reassemble the alternator, replacing the voltage regulator will cost you less than $20. Last one I bought was about $12. The 12si, 15si, and 27si all use the same regulator.

The "solenoid looking part" may be exactly that. A solenoid is nothing more than a relay, and they are commonly used as isolators in multi-battery installations. The blue thing that Skip426 posted is a solid state isolator. They both do the same thing. Here is an example:
Amazon.com: PAC PAC-80 80-Amp Relay Battery Isolator: Automotive

[whem2fish]

Open the drivers hood your isolator is right above the fuses you have 2 solidodes one is for the battery when in the dog house it will be on the right the one on the left lets you Guarneri all battery's

[ahicks]

The solenoid near the alternator has to do with the "hot start" issues involving the 454's.

If the starter is engaging it's working as designed.

The 15.8 volt reading was accomplished while connected to a battery? Where did you get that reading?

[ken swick]

Originally Posted by whem2fish

Open the drivers hood your isolator is right above the fuses you have 2 solidodes one is for the battery when in the dog house it will be on the right the one on the left lets you Guarneri all battery's

Yep ...found them. Thanks

[ken swick]

I took the reading at the start battery pos terminal. Bat was 12.34 prior to engine start up and 15.8 with engine running. Thanks

[ken swick]

Originally Posted by Kurmudgeon

Your alternator is most likely a Delco 12si, internally regulated. If it's rated output is greater than 94 amps, it would be a 15si or 27si. Have you tested output with a known accurate voltmeter? Dash gauges are not known for their accuracy.

If it is actually putting out too much voltage you have two options:
1) Easy and expensive is to replace the alternator.
2) A little more difficult and far cheaper is to replace the voltage regulator. If you have the mechanical skills to disassemble and reassemble the alternator, replacing the voltage regulator will cost you less than $20. Last one I bought was about $12. The 12si, 15si, and 27si all use the same regulator.

The "solenoid looking part" may be exactly that. A solenoid is nothing more than a relay, and they are commonly used as isolators in multi-battery installations. The blue thing that Skip426 posted is a solid state isolator. They both do the same thing. Here is an example:
Amazon.com: PAC PAC-80 80-Amp Relay Battery Isolator: Automotive

Thanks for your input. At this point it looks like a new alternator. There are times when the alternator works fine and then
it suddenly jumps to off scale high.

[38Chevy454]

Agree with Kurmudgeon, if you can just replace your internal voltage regulator, it is cheaper. It can take a bit of mechanical skill, here is a trick: use a toothpick/paperclip or similar to hold the brushes in place when you put it back together. Your alternator is internal VR, but it may be overvoltage due to bad ground connections. The alternator, and therefore the VR, has to have good reference voltage and grounds.

[Dr4Film]

Why not remove it and have the whole thing rebuilt with new internal parts including the voltage regulator. Probably between $100 - $200 to have a reputable rebuild shop do the task.

Dr4Film ----- Richard

[Kurmudgeon]

Originally Posted by Dr4Film

Why not remove it and have the whole thing rebuilt with new internal parts including the voltage regulator. Probably between $100 - $200 to have a reputable rebuild shop do the task.

If you don't have the necessary skills or tools to rebuild it yourself, that is probably the best option. Having it rebuilt by a local shop will probably net you a better quality job than buying an over-the-counter rebuilt that was likely done in China. Those can be a crap shoot. But they're fairly cheap. With shop labor rates these days over $100 an hour, a local rebuild ain't gonna be cheap. They'll hit you with a minimum 1 hour labor plus parts at full retail, which will probably be 3-4 times what you'll pay at the parts store.

But for a lot of us, myself included, a $200 rebuild is very hard to absorb, especially when a DIY rebuild will get you the same job for less than $20. After my post yesterday I checked current prices. A new regulator is still about $12, but a complete rebuild kit, with regulator, diode, bearings, and everything else needed, is less than $20. There aren't many parts in these things. And even a first timer should have it done in less than an hour.

And there's one more thing . . . the satisfaction of knowing you did it yourself. Priceless.

[Dr4Film]

Originally Posted by Kurmudgeon

If you don't have the necessary skills or tools to rebuild it yourself, that is probably the best option. Having it rebuilt by a local shop will probably net you a better quality job than buying an over-the-counter rebuilt that was likely done in China. Those can be a crap shoot. But they're fairly cheap. With shop labor rates these days over $100 an hour, a local rebuild ain't gonna be cheap. They'll hit you with a minimum 1 hour labor plus parts at full retail, which will probably be 3-4 times what you'll pay at the parts store.

But for a lot of us, myself included, a $200 rebuild is very hard to absorb, especially when a DIY rebuild will get you the same job for less than $20. After my post yesterday I checked current prices. A new regulator is still about $12, but a complete rebuild kit, with regulator, diode, bearings, and everything else needed, is less than $20. There aren't many parts in these things. And even a first timer should have it done in less than an hour.

And there's one more thing . . . the satisfaction of knowing you did it yourself. Priceless.

Jim,

I totally agree that if one has the skills to do the job it is an easy task. I done my share of them when younger. But now I choose to hand over that task among many others concerning engine work to those qualified to do it.

I have only been bitten once by the Cummins shop in Coburg Oregon who did over $450 worth of useless Blow-By tests on my engine only to tell me there was nothing wrong but yet when climbing the Siskiyou Pass on the way south I had oil all over the rear of my coach and trailer once again. The Cummins Shop in El Paso Texas solved the problem.

Dr4Film ----- Richard

[ken swick]

Originally Posted by Kurmudgeon

If you don't have the necessary skills or tools to rebuild it yourself, that is probably the best option. Having it rebuilt by a local shop will probably net you a better quality job than buying an over-the-counter rebuilt that was likely done in China. Those can be a crap shoot. But they're fairly cheap. With shop labor rates these days over $100 an hour, a local rebuild ain't gonna be cheap. They'll hit you with a minimum 1 hour labor plus parts at full retail, which will probably be 3-4 times what you'll pay at the parts store.

But for a lot of us, myself included, a $200 rebuild is very hard to absorb, especially when a DIY rebuild will get you the same job for less than $20. After my post yesterday I checked current prices. A new regulator is still about $12, but a complete rebuild kit, with regulator, diode, bearings, and everything else needed, is less than $20. There aren't many parts in these things. And even a first timer should have it done in less than an hour.

And there's one more thing . . . the satisfaction of knowing you did it yourself. Priceless.

I am just back from Orient Point Long Island. I will dive into the alternator tomorrow. I will take it off and then have it tested at Napa ... the test ought to lead me in the right direction. Since we want to get one more trip in this Fall, I think I will replace the alternator and keep the old one to tinker with. Thanks!!!

[Rvbuzz]

If the alternator tests fine on the bench tester then you have three possible problems.

1. Is the reference voltage. This is the larger of the two wires at the plug of the alternator. This should be that same as battery voltage. It tells the regulator how much to charge.

2. Is a high resistence between the alternator and battery. Starting at the battery when it is overcharging, check voltage at battery, isolator and alternator (battery terminal and reference wire). Note all voltages should be within .3 vdc.

3. battery may have lost it capacity for resistence. Have battery tested.

If there is a local alternator/starter rebuilder check with them to see what they charge for rebuilding. I owned a rebuilding company in the 80's and Delco 10 and 12 SI alternators were pretty cheap. Theses are very easy alternators to rebuild. All you need is common tools.