Vacuum erratic when electric fans turn on

[RustyPile]

Originally Posted by forestb

All that I know is that I used the alternator as a 3 wire when I first bought it in 2009. I then started using it as a one wire around 4 years ago. When I was running it as a 3 wire I had removed the external regulator and put an adapter on on the plug that used to plug into the regulator that rerouted those wires.

I do understand that the voltmeters are not vary accurate. What is a DMV?

I had the battery checked today and it was still in good condition. I took the alternator to get tested but they could not figure out how to hook there Machene up to it. I did notice that when I reinstalled my battery that positive battery cable sparked a little when it touched the post. I have heard that this might mean that I have a ground problem. Also maybe I just need a new alternator sense mine is now 13 years old.

DVM = digital volt meter. What did you use to take those various voltage readings?

If the place that checked your alternator didn't know how, you went to the wrong place. Simply mount the alternator to the machine and hook up ONE WIRE. Spin up the machine and check the output under full load. You need to deal with somebody else..

I think I understand why M.A.D. suggested you stay with a one wire alternator. They aren't complicated to install... I don't like them for several reasons, but what really turns me off to them is the fact that you have to rev the engine so high to get them "excited".

What I'm about to tell you I mean it with absolutely no insult nor disrespect meant. You don't have enough experience or skills to handle electrical work. Reading wiring schematics/diagrams is number one when dealing with electrical problems. Knowing what and how to use the proper tools is also a requirement.

Neither a one wire nor three wire alternator requires an external regulator. So, if you had, or now have an external regulator hooked up, that's one of your problems. Just out of curiosity, what changes did you make to the alternator to switch it between 3 wire and one wire?? Did your battery have to be brought up to full charge before load testing it? If it came off the vehicle fully charged, your charging system is working.

Since I mostly build my own wiring harnesses, I can't truthfully recommend a plug-and-play charging harness.

[forestb]

I used a multimeter that I borrowed from a friend. It is old and beat up and I was not exactly sure what I should be setting it to. I bought a new one yesterday and will try it again today.

I agree that the guy didn’t know what he was doing. Just a kid pushing buttons.

Yes when I took the battery in to be tested it had only been charged by the vehicles charging system and I had not driven it for a day or 2

I agree that I don’t have the proper skills. I am definitely no electrician nor am I a mechanic. But as is common on this sight I as a straight forward question and then I a find myself in the deep end of troubleshooting.

No changes were made to the alternator when switching over that I know of. That was done when I had a mechanic install a painless performance wiring harness.

The original alternator that was in the truck when I bought it was a three wire that was connected to a little black box that I assumed was an external regulator. When that alternator went bad I wanted an internally registered alternator so I purchased the alternator that I have now. When installing that alternator I connected a rerouting plug to the plug that originally connected to the external regulator.

[forestb]

So I ran some tests with the new multimeter.
12.5 at battery with engine off
14.6 at battery with engine on
13.7 volts with radio, electric fans and ac turned on.
14.7 volts at alternator post engine on and radio fans and ac off.

I was not able to test the voltage at the distributor because I can’t seem to get a reading from it. Maybe I am doing it wrong. How should I go about testing the volts at the distributor? Which also brings me back to my original question of whether my fans coming on should cause my vainest to drop slightly and waver back and forth slightly.

It looks like my biggest problem was a faulty multimeter. Unless somehow I fixed something while removing and reinstalling alternator and battery.

[RustyPile]

Originally Posted by forestb

I used a multimeter that I borrowed from a friend. It is old and beat up and I was not exactly sure what I should be setting it to. I bought a new one yesterday and will try it again today.

I agree that the guy didn’t know what he was doing. Just a kid pushing buttons.

Yes when I took the battery in to be tested it had only been charged by the vehicles charging system and I had not driven it for a day or 2

I agree that I don’t have the proper skills. I am definitely no electrician nor am I a mechanic. But as is common on this sight I as a straight forward question and then I a find myself in the deep end of troubleshooting.

No changes were made to the alternator when switching over that I know of. That was done when I had a mechanic install a painless performance wiring harness.

The original alternator that was in the truck when I bought it was a three wire that was connected to a little black box that I assumed was an external regulator. When that alternator went bad I wanted an internally registered alternator so I purchased the alternator that I have now. When installing that alternator I connected a rerouting plug to the plug that originally connected to the external regulator.

So you still don't know if the alternator is good or bad. Let me guess. You took it to a "chain store", such as AutoZone, O'Reillys, etc..

I can tell you this with 100% certainty. A one wire alternator does not need nor have provisions for more than one wire. That excludes the circuit for the charge warning light. The referenced "one wire" connects to to the large output post on the rear of the alternator.. The other end of that wire joins the main power distribution wire and winds it's way back to the positive terminal of the battery. if you have a functioning charge light, there will be a second wire connected to one of the two side-by-side terminals on the alternator.

These same two wires are found on a three wire unit. A third wire, referred to as the "voltage sensing" wire is connected to the other side-by-side terminal.

If the voltage is below 13.5 when the engine is running, and everything electrical turned on, this indicates one or two (possibly more) problems.. #1 item to look at is the alternator output. Find someone knowledgeable and capable to check it for you.. If it checks ok, you need to look at the wiring. The charging circuit may be too light (wire gauge too small) to handle the higher demands. You also may have loose or corroded connections somewhere.. I suspect, your one wire alternator can't reach it's full capacity because of the way it's wired.. Those electric fans draw a minimum of 18 - 20 amps EACH. Even more at fan start up. Except for "turn on" signals, they need to be on circuits totally independent of the other wiring, complete with fuse links, relays, and circuit breakers. Faulty wiring is one of the major causes of vehicle fires. I seriously suggest you find a good automotive electrician and have him clear up this wiring mess.

[RustyPile]

Originally Posted by forestb

So I ran some tests with the new multimeter.
12.5 at battery with engine off
14.6 at battery with engine on
13.7 volts with radio, electric fans and ac turned on.
14.7 volts at alternator post engine on and radio fans and ac off.

I was not able to test the voltage at the distributor because I can’t seem to get a reading from it. Maybe I am doing it wrong. How should I go about testing the volts at the distributor? Which also brings me back to my original question of whether my fans coming on should cause my vainest to drop slightly and waver back and forth slightly.

It looks like my biggest problem was a faulty multimeter. Unless somehow I fixed something while removing and reinstalling alternator and battery.

Those readings are acceptable, but just barely.. I don't like the readings at the battery and alternator with the engine running.. 14.7 is about .5 volts too high, but that's indicative of a one wire alternator.. This could lead to boiling the electrolyte out of the battery and premature bulb failure With internal voltage sensing, it doesn't know what the voltage of the battery, and more important, upstream of the battery. Something else to consider. If you bought a cheap quality meter, it's accuracy could be questionable.

I haven't re-read this thread entirely, so I'll just ask. What distributor do you have? If an HEI, has the resistor wire been removed, or at least bypassed going to the distributor. It needs to be replaced with a 12 ga. non-resistor wire. If you have an HEI, voltage can be checked by inserting the end of a paperclip into the terminal labeled "BATT".. Clip the DVM lead to this paperclip. Ground the other DVM lead and take a reading.. With the engine running, it should be at or very near (within .1 volt) of the reading at the battery. FYI, the ignition module doesn't like to have more than 14.2 volts applied.

[forestb]

Originally Posted by RustyPile

So you still don't know if the alternator is good or bad. Let me guess. You took it to a "chain store", such as AutoZone, O'Reillys, etc..

I can tell you this with 100% certainty. A one wire alternator does not need nor have provisions for more than one wire. That excludes the circuit for the charge warning light. The referenced "one wire" connects to to the large output post on the rear of the alternator.. The other end of that wire joins the main power distribution wire and winds it's way back to the positive terminal of the battery. if you have a functioning charge light, there will be a second wire connected to one of the two side-by-side terminals on the alternator.

These same two wires are found on a three wire unit. A third wire, referred to as the "voltage sensing" wire is connected to the other side-by-side terminal.

If the voltage is below 13.5 when the engine is running, and everything electrical turned on, this indicates one or two (possibly more) problems.. #1 item to look at is the alternator output. Find someone knowledgeable and capable to check it for you.. If it checks ok, you need to look at the wiring. The charging circuit may be too light (wire gauge too small) to handle the higher demands. You also may have loose or corroded connections somewhere.. I suspect, your one wire alternator can't reach it's full capacity because of the way it's wired.. Those electric fans draw a minimum of 18 - 20 amps EACH. Even more at fan start up. Except for "turn on" signals, they need to be on circuits totally independent of the other wiring, complete with fuse links, relays, and circuit breakers. Faulty wiring is one of the major causes of vehicle fires. I seriously suggest you find a good automotive electrician and have him clear up this wiring mess.

Did you see the numbers in my last post before posting this? Or did you see the numbers and still feel that I have problems? Never mind just saw your lady post

[forestb]

So I’m using a multimeter and have it set to dvc 20 when testing the battery and alternator. When I internet the probe into the battery terminal on my hei distributor the number goes all over the place. From .02 up to over 12. Do I have it at the correct setting?

[forestb]

Here’s a photo of the multimeter settings.

[RustyPile]

Originally Posted by forestb

So I’m using a multimeter and have it set to dvc 20 when testing the battery and alternator. When I internet the probe into the battery terminal on my hei distributor the number goes all over the place. From .02 up to over 12. Do I have it at the correct setting?

You have the meter set correct. Your probe probably isn't making good contact with the distributor. You should see a steady reading that's the same or very near the same as the reading at the battery. Did you use a paper clip or small stiff wire like I suggested?

That wire connected to the output post on the alternator connects to the main power distribution wire. That wire goes EVERYWHERE, and has several factory splices. It brings power to the fuse box. It powers the ignition switch, headlight switch, and goes to the battery. When you turn on the ignition switch, power goes from there to the fuse box in addition to going to the distributor.. All these wires have to be of sufficient gauge to carry all that current. If there is a breakdown in the connections anywhere, there will be a voltage drop across that connection.

The point I'm making is you have to know how all this stuff works. You have to know how, where, and when to use that volt meter. The electrons (current) flowing through those wires is invisible, the volt meter is your eyes. There's no cut and dried solution to your problem, but there is a systematic approach to finding it.

A vacuum gauge is not used to track down electrical problems. I worked as a mechanic for over 30 years. Much of that time, I solved and repaired driveability issues. I never used a vacuum gauge for solving electrical issues. Plus, (and I say this at the risk of starting a fire storm) I hardly ever used one for solving other issues.

I'm thinking you have more than one problem causing the erratic engine run. If the battery was properly tested, your alternator is keeping the battery charged. But that's all it's doing. I think those high current demand radiator fans are wired in wrong. When they come on, even though the voltage at the battery is held to spec, the voltage to the distributor is somehow pulled down, causing the ignition module to "act up". That's just a supposition on my part, but that's the first place I'd look.. Get that meter substantially connected to the BATT terminal on the distributor and get an accurate reading.

There's a lot more material that needs to be discussed. Are you up for a phone conversation? If so, PM me your phone number and I'll give you a call.

[forestb]

When I was using the vacuum gauge it was so that I could adjust the mixture on my carburetor it had nothing to do with trying to find an electrical problem. I don’t known if this makes a difference but my lights fans and ac are all on relays. I was able to get the probe into the socket far enough but it still gave me varying readings on both the bat terminal and the other one. Maybe the probe wire is too close to a spark plug wire and reading that instead. I might send you my phone number at a later time. I am tired of thinking about it right now.

[RustyPile]

Originally Posted by forestb

When I was using the vacuum gauge it was so that I could adjust the mixture on my carburetor it had nothing to do with trying to find an electrical problem. I don’t known if this makes a difference but my lights fans and ac are all on relays. I was able to get the probe into the socket far enough but it still gave me varying readings on both the bat terminal and the other one. Maybe the probe wire is too close to a spark plug wire and reading that instead. I might send you my phone number at a later time. I am tired of thinking about it right now.

Here's a simple explanation about the vacuum reading.. Depending on the camshaft profile, the vacuum reading should be fairly steady. There's no magic number to shoot for. Regardless of what "they" say, the highest vacuum reading is not indicative of the proper set point for the idle mixture screws.. "Feel" and a tachometer are better indicators.

That's all well and good about the fan relays.. BUT, are they properly wired into the electrical system?? Apparently not. When you were able to get a reading with the old meter, you said there was a voltage drop at the distributor when the fans came on.

Most of the time when lights aren't bright enough, it's because the wiring and/or alternator isn't heavy enough to support the current demands.. Lights are very voltage sensitive and the first things that show the effects of low voltage.. I'm not a fan of putting factory installed lights on relays. That's just a Band-Aid to cover a problem. In my opinion, the only reason for putting lights on relays is because aftermarket lights place a heavier than normal load on the factory wiring..

I wouldn't assume anything about that distributor reading you're getting. Although what you say could be what's happening, I've never experienced that. But my meter is a high quality one. Regardless, you need to know what the voltage is with the system under full load. My #1 suspect is that you aren't getting a good contact between the terminal and the probe. While I'm on this subject. We don't need a reading on the "other terminal". That's the hookup point for a tachometer. Voltage readings there are meaningless. BTW, if you don't have a tachometer, get one.. I don't mean get one mounted inside the truck. You need one that can be temporarily connected to the engine and hung under the hood some place. To be used for diagnostic work.

Ok.. I understand this stuff can be exasperating. I'll shut up now and wait to hear from you..

[forestb]

I have h4 bulbs. That’s why they have relays. I will try again later to get a correct reading from the distributor and get back to you.

[cadillac_al]

This is why when I buy a vehicle I seem to end up putting it back to stock configuration. I never had a problem with GM alternators or GM clutch fans. My 76 GMC has the brightest spot lights in the driveway and they are just stock halogens.

[The Rocknrod]

Well I will tell you that I also run that alt on my truck. I ensured that I ran it as a 3 wire from the start. Also the sensing wire is run, like I said earlier as far away from it as possible near the battery. Also youll have to run a diode in the other wire. Doesnt miss a beat. I read and "understood" why I wired it as I did.

[forestb]

With the multimeter connected to the hei distributor and the wire not touching any spark plug wires the readings are still all over the place. Here’s a link to a video.

https://m.youtube.com/watch?v=bLyMFp...ature=youtu.be

[forestb]

That was with the fan off. The highest number it got to with the fan off is 14.28 and the highest with the fan on was 13.84. That is the highest of the changing numbers.

[RustyPile]

Originally Posted by forestb

With the multimeter connected to the hei distributor and the wire not touching any spark plug wires the readings are still all over the place. Here’s a link to a video.

https://m.youtube.com/watch?v=bLyMFp...ature=youtu.be

I wouldn't trust those readings as far as I can throw your truck.. Giving them the benefit of the doubt, you probably have a loose connection somewhere. You'll never get a decent engine run with those readings. But before I'd go digging around trying to find it, I'd use another meter of known good quality and check voltage again.

[forestb]

I am grounding the multimeter on the frame is that a good location? I will see if I can get my hands on a better multimeter.

[RustyPile]

Originally Posted by forestb

I am grounding the multimeter on the frame is that a good location? I will see if I can get my hands on a better multimeter.

If you have a good network of ground straps, the actual location where you ground the DVM is of no consequence. Just be sure you have a good bare metal connection. If the ground strap between the engine and body is a bare braid, clip the meter's negative to that.. When I said "loose connection", that includes the contact of the DVM leads to the truck.

I always use alligator clip adaptors that plug onto the DVM leads or alligator clips attached directly to the leads. I some time use a jumper to extend the length of the lead. I have a large assortment of various length and size jumpers -- all the way from 20 ga with small alligator clips to jumper cable size.. Some of my jumpers are 12 - 15 feet long. Back in the day when I was "gainfully employed", the majority of my jobs were electrical so I am well equipped with electrical tools.

[forestb]

Can you recommend a specific DVM?

[Getter-Done]

https://www.oreillyauto.com/detail/c...m0/w2972?pos=1

[RustyPile]

Originally Posted by forestb

Can you recommend a specific DVM?

I have an older version of this Craftsman. Mine came with a storage case. Not sure about this one. https://www.lowes.com/pd/CRAFTSMAN-A...ter/5000054921

I also have a 20 year old Fluke, the benchmark brand.

[EDIT]
I just remember. I built a new shop about 7 years ago and did the electrical wiring myself. I'd forget my meter when I'd go to work on the shop. I bought this Southwire meter and would leave it there when I'd finish for the day.

https://www.southwire.com/tools-equi...v/p/p-65031240
I like this one. It's easy to read/use. The probes fit in pockets on the rear for storage. It also has an auto power off feature so the battery doesn't run down if you forget to turn it off.

[RustyPile]

Originally Posted by forestb

Can you recommend a specific DVM?

Here's a link to those alligator clip adaptors I spoke of.
https://www.southwire.com/tools-equi...s/p/p-58292940

[cadillac_al]

Originally Posted by forestb

Can you recommend a specific DVM?

I bought this cheap one recently and it's the best one I ever had. It's idiot proof. I don't have to select the correct volt range or ohm range etc.

https://shop.advanceautoparts.com/p/...al+multi+meter

[The Rocknrod]

I'm glad I got a Fluke a couple years ago (as a present of course).