Low voltage at idle with AC running

[ccallana]

Now that it is getting warm (mid 90s the last 2 days) - my new Griffiths AC is getting properly worked out - producing some nice cold air in the cabin.. love it!

I changed out my USB charger in the cigarette lighter spot with one that shows voltage. At speed on the freeway getting 13.5ish Volts - which seems to be ok..sometimes dropping below 13, but not often.

At idle, at a stop light - drops down around 12, sometimes even 11.8 or 11.9 -

I don't sit at idle for long of course - so I'm not draining battery to a point where I'd see problems I think...

So question is - long term, is this bad for the electrical system? Should I really be looking to update my alternator? (WOSP?) - or just a newer battery?

Any thoughts?

[blucille]

I’d think your 3.2’s factory alternator puts out enough amperage to cover the griffiths AC system. I’d check the chassis grounds, but it might be time for an alternator rebuild. No need for the WOSP unit. I run a 3.6 with the full Mr Ice package from Griff, never see voltage below 12.5 and a steady 14 when cruising. Truth of it is that, unless you spend more time idling than driving, your battery is going to be fine.

[porschedude996]

You might check the voltage with a high accuracy meter to verify you’re not chasing your tail. Also, you might make sure you idle is 950 rpm.

[Duc Hunter]

Almost all alternators do not put out much amperage (power0 at low RPM. I forget the numbers now, think I posted them in my long electric A/C thread……it’s something like a standard alternator in a car like the 3.2 will put out 25 amps at idle. Thats why headlights can dim slightly, interior lights etc. 12000-1500 RPM they are pretty good, and probably making max power by 2000 RPM. Some cars even run pulley that under drives the alternators for more HP. The Classic Retrofit alternator makes massively more power (amperage) at idle, and was specially designed to do so to support their A/C. I think it makes almost as much at idle (90amps or something) as the 3.2 ever makes. Even your Grifiths A/C draws a lot of current at idle, between the powerful blower fan, the condenser fan(s), etc. Also remember the A/C compressor does not work as well at idle. Even in my 2021 Jeep Wrangler, the air gets MUCH colder if I am at a stop light and rev the motor to say 1500 RPM. Good luck with your challenges.

[kuehl]

Ccallana is not running the high out put evaporator motor. And, the 2 added fender condensers with fans do not add enough amp draw to cause battery amp capacity issues. And, he has the variable fan speed controller which tends to lower overall amp consumption.

He could do battery and alternator tests just to check how they are holding up; better to be proactive then find yourself stranded.

Even the factory A/C draws a lot of current at idle; never mind when you turn on high beams.

Statistically, with Griffiths systems out on the road nearing the 30 year mark, now worries here.

[pavegeno]

I did this and it solved all of the same issues. Voltage sits high 13s to low 14s. I have full Griff’s with the dual Keuhl in the LR wheel well. Good luck.

https://www.classicretrofit.com/en-us/collections/upgraded-alternators/products/porsche-911-high-output-175a-alternator-kit-1984-1989

[ccallana]

Originally Posted by kuehl

Ccallana is not running the high out put evaporator motor. And, the 2 added fender condensers with fans do not add enough amp draw to cause battery amp capacity issues. And, he has the variable fan speed controller which tends to lower overall amp consumption.

He could do battery and alternator tests just to check how they are holding up; better to be proactive then find yourself stranded.

Even the factory A/C draws a lot of current at idle; never mind when you turn on high beams.

Statistically, with Griffiths systems out on the road nearing the 30 year mark, now worries here.

Thanks Griff! Correct - running the standard Evap fan motor -

Probably a good idea to get more accurate measurements than the $10 USB readout Battery is pretty old actually.

Thanks all for the comments and suggestions.

[GH85Carrera]

I have pretty much the full Griffith's upgrade. 4 condensers, all new hoses, hurricane blower, variable speed fan controller, and temp controller. I do have the OEM original front and rear condensers, and no need to upgrade them as I get 38 degree air on hurricane velocity, on a 107 degree day after driving for 10 hours.

My old alternator was rebuilt 25 years ago and I noticed it was starting to rattle and the bearings were going bad. I tried to have it rebuilt, but the only local guy I could find did not get something right, and now he seems to be out of business.

I bought a brand new Valeo alternator. Now it sits at 13 volts even at idle with the brakes on, and the AC blowing at max. Once off of idle, it goes to 13,5 volts.



I had my tachometer changed to add a voltage gauge where the stupid shift light was. This was years ago, as I have almost 199,000 miles now.

[PeteKz]

Same as Porshedude said: First check that your lighter/voltmeter is accurate. These are usually cheap Chinese crap and I've had several that were not accurate. There's only so much you can expect for just $10.

If the voltage is slightly low at idle with the compressor engaged, but comes up above 13.5 when you get above idle, dont' worry about it, that's normal, as others have suggested.