AC Fixed / engine power low w/ AC On

[Flash66]

Hi Guys,

I finally got my AC system 100% with a new compressor, thorough flush, vac and recharge. (Thanks NightFlyer and DaveDMCMW!) Noticed with the AC on, in first gear my car could barely make it up the slight step into my garage bay without it struggling. Turn the AC off and power seems fine again. It's almost like trying to start off in 3rd gear with the AC on. The fuel system has just been redone, completely clean, new Hervey style long neck pump, tuna can W/ new screen, new cap, plugs, wires, rotor and runs good, no idle hunt. Was sputtering a bit cold after sitting for a month while I'm doing my restoration but smoothed out after warming up. Again it only seems to be struggling with the AC running. I do have the charcoal canister removed due to my engine bay restoration, but have the vac ports plugged. Any ideas? Thanks in advance!

[NightFlyer]

What transmission does your car have?

[Flash66]

Manual 83 5spd

[NightFlyer]

That's really weird.

Does it only happen when the engine is cold, or warm (regular running temp) as well? Also, where does your car idle at (RPM) both with the A/C on and off?

Can you try it with the A/C engaged, but the cabin blower/fan off (on 0), and see if you get the same results or something different?

[Flash66]

I'll have to recheck the RPM off but noticed 900 with AC on. The engine was warm and noticed after running for a good hour charging the AC and adjusting the LPS. Drove the car from my house to my shop about 500' away and noticed the loss of power. Come to think of it, it was idling a bit rough but not hunting.

[NightFlyer]

I'll have to recheck the RPM off but noticed 900 with AC on. The engine was warm and noticed after running for a good hour charging the AC and adjusting the LPS. Drove the car from my house to my shop about 500' away and noticed the loss of power. Come to think of it, it was idling a bit rough but not hunting.

Check the idle again (A/C both off and on) and get back to us - a video would be great if you have that capability :)

[Bitsyncmaster]

I would think the AC would only take a few HP when running. I would not think you could even notice it unless your comparing the power at idle speed.

Maybe it a low voltage issue.

[Flash66]

Will do! I just remembered that while refurbishing my entire engine compartment I remember knocking the plastic cap off of the mixture screw and it went straight to another dimension. Lost forever. I'm wondering if that vacuum leak could be bad enough to cause such a power loss. Got to figure out a good replacement for this and try again! If no luck I'll post a video. Thanks for the support fellas!

[Flash66]

Thanks Dave, that's another thing that crossed my mind. My batt is on its last leg and jumped it off to charge the AC. Plus I'm still running the ducey and my voltages are always around 12 at best. Never any higher.

[NightFlyer]

Thanks Dave, that's another thing that crossed my mind. My batt is on its last leg and jumped it off to charge the AC. Plus I'm still running the ducey and my voltages are always around 12 at best. Never any higher.

Electrical power issue was one of my guesses as well, but didn't want to mention anything until we had a better understanding of the symptoms here.

I'm still running the Ducey as well, and while under regular throttle, I'm usually pegged right at 13, sometimes a little more, and sometimes a little less. When in bumper-to-bumper slow moving traffic, such as I was during the Woodward Dream Cruise this last weekend, I usually sit around 11, sometimes a little more, and sometimes a little less, in which case I rev the engine a little just to get the alternator output voltage up.

[Flash66]

I would think the AC would only take a few HP when running. I would not think you could even notice it unless your comparing the power at idle speed.

Maybe it a low voltage issue.

Dropped $200 on a Optima yellow top battery and plugged up that mixture adjustment. Seems much better now. Oh and my engine spun over like a turbine! Thanks Bitsyncmaster! 30215

[hmcelraft]

Manual 83 5spd

What's an 83 doing with a Ducellier alternator?

[NightFlyer]

What's an 83 doing with a Ducellier alternator?

Good catch - I never looked at his VIN. :)

[NightFlyer]

Dropped $200 on a Optima yellow top battery

Ughh - Optima. :vomit_2:

For my opinions/thoughts about Optima, if you're curious/ or are so inclined, see the following:

http://dmctalk.org/showthread.php?7511-Better-Battery-Option%28s%29-Than-Optima

[Flash66]

What's an 83 doing with a Ducellier alternator?

That's true, it should be the Motorola then. Doesn't seem to be any better than the Ducellier as it seems pretty weak.

[hmcelraft]

Well, both of those alternators work close to their limits. If the battery is low to start with they can hardly keep up with demand AND recharge the battery. A fully charged battery is really needed with those two alternators in order to keep it charged when driving. If you drive infrequently you need to keep the battery charge maintained or at least disconnect the battery when it is not in use (assuming it isn't more than a month or two). A later technology alternator with more output - like 110 amps or more is good insurance. Maintaining the higher volts really makes things work much better. I like the Optima battery. I am on my second Red-Top - the first one lasted me 8 years. I have used one of Hervey's alternators all during that time - a 130 I think. I haven't had to put a charger or tender on the car yet. I use a marine 1000amp cut-off switch mounted on the battery cover to use when I put the car away. In the winter I usually get it fired up at least once a month(ish). During the good weather (or better weather) months I usually drive the car frequently.

[David T]

Well, both of those alternators work close to their limits. If the battery is low to start with they can hardly keep up with demand AND recharge the battery. A fully charged battery is really needed with those two alternators in order to keep it charged when driving. If you drive infrequently you need to keep the battery charge maintained or at least disconnect the battery when it is not in use (assuming it isn't more than a month or two). A later technology alternator with more output - like 110 amps or more is good insurance. Maintaining the higher volts really makes things work much better. I like the Optima battery. I am on my second Red-Top - the first one lasted me 8 years. I have used one of Hervey's alternators all during that time - a 130 I think. I haven't had to put a charger or tender on the car yet. I use a marine 1000amp cut-off switch mounted on the battery cover to use when I put the car away. In the winter I usually get it fired up at least once a month(ish). During the good weather (or better weather) months I usually drive the car frequently.

At idle under a big load it is all about the battery. At idle RPM's (below 1,000 RPM's) it really doesn't matter what alternator you have, they can't put out enough to cover the demand on the electrical system so the battery supplies what is needed. An old, weak, or undercharged battery can't do that so when the voltage drops below a certain level the ignition ECU calls it quits and the motor stops. Very similar to the other thread where the window switches kill an aftermarket radio. Digital stuff can't tolerate operating on low volts. As for the Optima's, they are expensive and troublesome. They have a "spotty" service record. Some last a long time and too many it seems die prematurely. A good Lead-Acid standard duty battery like an Interstate or Die-Hard is good enough and if taken care of can last 5 years or more. NEVER let a battery drain ALL the way down, freeze, or get hot while charging. If you are not using the car charge the battery for 1 day once a month and install a battery master switch.

[Ron]

I just remembered that while refurbishing my entire engine compartment I remember knocking the plastic cap off of the mixture screw and it went straight to another dimension. Lost forever. I'm wondering if that vacuum leak could be bad enough to cause such a power loss. Ya need to address this for sure.