Electrical Problem

rumrumm · October 09, 2006, 10:03:03 AM

I got my A/C charged and ready to go a month ago, so I was going to try it out on a one hour trip. So, I am cruising down the road, turn it on and am enjoying the cool air when all of a sudden the engine quit. I reached down, shut of the A/C, and the engine fired and started running again. About fifteen minutes later I try it again and the same thing happened. Obviously the pull of the A/C is too much. I run an electronic distributor, electric fuel pump and a SPAL 16 inch electric fan. The battery I am using is one of those small Odessey batteries mounted between the frame rails. Is the problem the alternator or the battery? My alternator is a 100 amp Powermaster, but the Voltmeter was reading 13.1 with the A/C on. All of the electrical stuff is run through relays. Help me understand how to fix this. Thanks.

enjenjo · October 09, 2006, 10:40:35 AM

Where are you getting the control power for the accessories? If you are tapping it off the ignition circuit, there may be enough voltage drop at the coil to cause the electronics to malfunction. You should have a seperate accessory circuit.

The other thing to check is engine ground. If the ignition is grouding through the AC compressor clutch, it can do this too.

Bruce Dorsi · October 09, 2006, 10:41:58 AM

Quote from: "rumrumm"Is the problem the alternator or the battery? My alternator is a 100 amp Powermaster, but the Voltmeter was reading 13.1 with the A/C on.

I don't have answers, Lynn, but I have questions!

Is it possible that an overdrive transmission has dropped the cruising rpms down to a level where the alternator is not producing its rated amp output?

Do you know the draw in amps of the components you are using? .....(You can temporarily install an ammeter in line at individual components, or at the individual circuits at the fuse block to check amp draws, to see what your total amp load is. ....This info is helpful to record and will aid in troubleshooting problems, years down the road.)

Are your wires able to carry the necessary currents? ......(It is possible to have adequate voltage, with inadequate amps, if resistance is too high.)

Some simple investigation, may avoid needlessly replacing components.

BFS57 · October 09, 2006, 01:06:48 PM

Hello;
I Can't and Can answer your problem! First, your alternator has to be putting out 14.2 volts! Next, have you run the alternator single wire or are you hooking up the internal regulator for voltage sensing?
If you don't have a clue what I am talking about go the the Mad Enterprises web site and do some reading.
My 57 Chevy has real electrical problems but soon I am doing a major re-wire and up grade using some of the things I have learned from the Mad website.
I have two cars that have given me electrical problems and I am slowly becoming a very knowledgable person when it comes to automotive electrical! I ain't no expert but not only am I acquiring the tools I need (have my own separate tool box for auto electric) and am filling my box with any and all supplies for any kind of electrical job.
If your car is fiberglass (like my Vicky)) grounding may seem good but I am now in the design mode to hook ground "leads" to the major ground strap and take these inside where I will use terminal strips to re do the grounds inside the car!
You have no idea how much a difference well grounded accessories perform unless you see for yourself.

Bruce

Leon · October 09, 2006, 02:33:46 PM

Even on a steel car it's important to make sure everything is properly grounded. I found that heavy straps from the frame to engine and also the body have eliminated gauge probems, and separate grounds to the front clip sheet metal keep the headlights operating properly.

rumrumm · October 09, 2006, 03:16:07 PM

I think everything is properly grounded but I will double check that as the grounding is the first place to look if you have problems. But I am wondering since it is a one-wire alternator, and since I am only running 2100 rpm in o.d., whether the alternator is making enough current. Isn't the electrical system running off the current made by the alternator in a situation like this?
I wonder if converting my one-wire alternator back to a three wire will produce more current so I won't have this problem. In case you are wondering, here are the specs on my battery: www.odysseybatteries.com/battery/pc680mjt.htm

Leon · October 09, 2006, 06:00:49 PM

I have a Powermaster and they rate the output at 2400 rpm whether it is hooked up as a one wire or 3 wire. But, that is alternator rpm and since most vehicles run about a 3:1 ratio, it should be putting that out at 800 engine rpm. At 2100 rpm in OD the alternator should be turning over 6000. The main difference in converting to 3 wire is not having to rev the engine to get the alt. to "kick in" when first starting, and the ability to remote sense to make up for voltage drops in various wiring situations. Powermaster said I should have between 13.6 and 14.6 volts when cruising so 13.1 may indicate something is low.

rumrumm · October 10, 2006, 08:52:58 AM

I think I may have found the answer. Here is a response from another website:

the PC680 is a 17 ampre-hour battery.

You have a relatively high amperage draw......
fuel pump.......possibly 6 amps
electric fan.... possibly 15 amps
compressor clutch.... 8 amps
blower motor ..on high...15 amps

these are just proximations. You can calculate the draws individually.

Now consider also that the Odessey and other starved electrolite batteries of that design, when in a discharged condition of about 40% or less might not function well using an alternator.

So you have inadaquate battery volume...now the alternator ,then, may or may not be able to pick up the battery. 14.7 to 15 volts is needed in a charging rate.

In addition..you should be running relays in the fan and AC circuit both.... which you say you have.

Short answer...relays and at least a 925 Odessey or bigger.

Dave · October 10, 2006, 05:58:45 PM

Quote from: "rumrumm"I think I may have found the answer. Here is a response from another website:

the PC680 is a 17 ampre-hour battery.

You have a relatively high amperage draw......
fuel pump.......possibly 6 amps
electric fan.... possibly 15 amps
compressor clutch.... 8 amps
blower motor ..on high...15 amps

these are just proximations. You can calculate the draws individually.

Now consider also that the Odessey and other starved electrolite batteries of that design, when in a discharged condition of about 40% or less might not function well using an alternator.

So you have inadaquate battery volume...now the alternator ,then, may or may not be able to pick up the battery. 14.7 to 15 volts is needed in a charging rate.

In addition..you should be running relays in the fan and AC circuit both.... which you say you have.

Short answer...relays and at least a 925 Odessey or bigger.

Lynn im sorry but ive got a real hard time believing that a 100 amp alt wont keep up? 100 amps is big amps even at 13.8-14 volts. Your battery is a storage device and holds 13.8 volts. Sure your using some amperage with all the junk running but thats what the alt is for and at 100 amps it should kick azz.
Id believe the alt is bad before any battery problems.
Oh ya i have been wrong before.....
Dave

rumrumm · October 11, 2006, 07:54:27 AM

Before I shell out money for a new battery, I am going to try another alternator. I have another never-been-out-of-the-box new 100 amp alternator, so I will switch them out this weekend and see if that makes any difference.

Dave · October 11, 2006, 12:17:55 PM

Quote from: "rumrumm"Before I shell out money for a new battery, I am going to try another alternator. I have another never-been-out-of-the-box new 100 amp alternator, so I will switch them out this weekend and see if that makes any difference.

hummmmmmm i went back and looked at the battery site and all i can say is wow! im supprised you can get it to start

looks like a motorcycle battery? why so small :?: ..yup id still try the new alt just for fun. i was thinking i had a power master on my coupe and they could be wired up single or 3 wire :?: I know mine can but id have to look at the brand again. I was going to change it to 3 wire cause i have a habbit of not reving it enuff when its warm and the dam thing doesnt go to charge mode.
dave :!:

Mikej · October 11, 2006, 05:26:52 PM

What your thinking is that as soon as you turn the A/C on your battery is going dead? What I would think is the A/C circuit is effecting the Ignition circuit. Going thru it to ground. Not heavy enough wire to your circuit panel. I think a one wire alternator needs the sense voltage to begin to charge ( rev up the engine) than its good till you shut it back off.

donsrods · October 11, 2006, 11:24:27 PM

I looked at that battery site, and have to ask if anyone knows anything about these. In the T modified I'm building there is very little room for a battery by the rear axle, and I can't put it anywhere else because the car is super low.

One of these would be ideal, but are they capable of cranking a sbc? I have no accessories in this car except for an electric fan and fuel pump. I would hate to design the battery box around this battery and then find out it is too small.

Not trying to hijack this thread, but felt my question might tie in with it. Thanks for any info anyone might have.

Don

rumrumm · October 12, 2006, 08:33:36 AM

I have had no problems with this battery until I tried to run the A/C. And I run electric fuel pump and an electric fan as well as a stereo (no amp). I am changing alternators this weekend to see if that makes any difference. I'll keep you posted regarding the nature of the problem when I find it.