I know there are several threads on this topic but I didn't find one specific to my problem. Maybe I didn't look hard enough?

My 1969 442 has a built engine from Mondello with a big hydraulic roller cam. It also has a manual trans and a conversion from a pulley cooling fan to dual electric cooling fans. The issue here is that when the engine is up to operating temp and I come to a stop light, the cooling fans kick on and the extra current draw on the alternator almost kills the motor. I'm assuming I have a stock alternator output.

I guess I could turn up the idle and call it a day but I would like to discover a better solution. A 100A alternator? Larger alternator pulley, etc.

Any suggestions?

Thanks,
-Martin

 

We need more info to be of real help. The amperage output of the existing alternator should be stamped in the casing e.g., 37A. The answer to decide what to do lies in the amp draw of the two fans, see if it is stamped in/on them and the alt output. Let us know and we can help more from there. What electrical options does the car have?

Good luck!!!

 

I highly recommend Powermaster. Made in USA and are tested. Have 150 Amp in my Olds since 2006. 150 Amps you can add a lot of accessory! Graph that came with it showed 107 amp at idle 134 amp at 1500.

2 Electric fans, elect fuel pump, 4 horns, elect water pump, powerful radio, Powermaster XS starter, aftermarket gauges, 4 high beams with two low beams switch, oil pressure switch to elect fuel pump, davies-craig digital gauge thermatic fan / EWP switch kit, Air/ Fuel meter. It adds up fast.

 

You can power my entire Ponderosa w/ that! Can you plug your car into your home main service panel during a power outage?

 

I did the same, but the Powermaster didn't last long. I had a local shop rebuild it for me and scaled it back just a bit. He told me it'd last longer if I did.

 

Must be the Chrome finish. Mine is Natural finish. https://www.summitracing.com/parts/pwm-47294/reviews 14 years with my right foot power adder.

Norrn, you know well 150 amp at 12 Volts is like 17 amp at 120 volt. Unless your Ponderosa is wired for 12 volts??

Old picture

 

Martin, the larger the alternator ampere rating, the more load it can put on the engine.

If your existing alternator nearly kills the engine at idle, putting on a higher-amp-rated one would put even more load on the engine and probably would kill it.

Ensuring your idle mixture is tuned correctly and possibly increasing idle speed will be required even if you put on a higher-amp alternator. You should do that now to solve the problem. No advantage in waiting.

 

It's actually a polished case, which has it's own issues.....

 

He said "I come to a stop light, the cooling fans kick on and the extra current draw on the alternator almost kills the motor." Sound to me the motors on the fan, draw a lot of amps.

 

I know. I just thought I'd pick an opportunity to be a smart-A$$. That is a Meaty Beaty Big and Bouncy alternator.

 

A alternator from a late 80s Cadillac with a 307 engine would be a big upgrade and a almost direct bolt in. The only modifications needed would be a upgraded charge wire from the alternator to the battery/horn relay, but that will need to be done no matter what alternator you install.

The next easy upgrade would be a CS series, it requires minor wiring changes. They are available up to 120 amps.

Then there are aftermarket alternators like power master.

 

If you upgrade to a higher amp alt. (Which in your situation I recommend). You will also have to increase the gauge of wire running from the alt to the horn relay. When i did mine I just added a second wire of the same gauge which basically doubles the amp carrying capacity, probably not exactly doubles it (this is a disclaimer for the engineers out there) but it will relieve the load on the factory wiring.

 

Wow, lots of responses. Thanks.

Answers to some of the questions:
1. Alternator is not original as it is chromed. I cannot find any stamping on it indicating the amps.
2. Accessories: air conditioning, convertible hydraulic pump (stock). No power windows or seats. Can't think of much else that would draw much current.
3. I have dual 12" cooling fans that have "12V 120W" on each. My calcs show 20A total. I have a variable speed controller running them.

To be clear, the only time idle is an issue is when the cooling fans kick on.

 

Maybe the best thing is to take it to autozone. Have them test the battery also. Do the headlights dim? Duralast have a limited-lifetime warranty.

If you are not going to add other electrical devices. You can get an 60 amp or more. If the fan are only 10 amp each.

You can check the amps going to the fans with a amprobe. If you have one or someone who does.

Duralast Gold New Alternator DLG7127M $90 New not rebuilt

• Part # DLG7127M
• SKU # 352098
• 63 amps
• Limited-lifetime warrant

RockAuto maybe cheaper. But if it bad to have to ship back.
Please let us know what you find!

 

The fans might draw only 20 amps running, but I bet it’s many times that during startup.

The advantage of the CS series is its common availability, and it puts out maximum current output just a little over idle.

Your current alternator might be rated at 60 amps, but that’s maximum output at elevated engine speed. The CS alternator I put on my Olds probably 20 years ago will put out 70-75 amps at idle, and maximum of 105 at maybe 1500 rpm.

Chances are good of being able to walk into any well stocked parts store and get a replacement CS alternator. That’s good if your 100 miles from home, your not likely to find a power master or one wire alternator without having to order one b

 

All good inputs. I think that VC455 made the good suggestion to look at the tuning of the carb first. I haven't touched it since I bought the car 2 years ago or so. The big cam does provide a very lumpy and tenuous idle but the carb idle circuit may need some attention. Seems like a good starting point. I'll look for threads on that topic.

Another note on the wiring of my car is that the previous owner did a lot of backyard engineering on the wiring especially in the alternator/regulator area. It's a mess. This may prompt me to do what I've been wanting to do and that is have the car rewired with one of those kits.

So much to do on that thing..... The good news is that the powertrain is pretty much done (except for a good tuning). The new Quick Performance Ford 9" rear end works great and the 4.11 gearing works well with the Tremec 6-speed.

 

Damm I don't know nothing about nothing but that's a busy engine bay, You go dude....