Voltage fluctuations

[Pentalab]

BBK, Steeda, Real Speed, and ASP UDPs cost around $250 while those from SR Performance cost a mere $157. I haven't heard of issues with any of them on the 05-10 GT.

Potential issue with any UDP is.... at idle, the alternator is spinning slower. Do folks really see any hp/tq gains with the use of a UDP ? Heck, ur water pump /alternator / AC and everything else will be spinning slower.

 

[Dino Dino Bambino]

Potential issue with any UDP is.... at idle, the alternator is spinning slower. Do folks really see any hp/tq gains with the use of a UDP ? Heck, ur water pump /alternator / AC and everything else will be spinning slower.

The UDPs do indeed slow down the accessories but there have been no reported issues with UDPs on a 4.6 3V. I've certainly have no issues on mine and my AC still blows cold on a 115*F day.
As for power gains, you're looking at roughly 9hp and 8lbft to the wheels so that's less than $30 per HP.

 

[DiMora]

If your running a cheap under drive pully set it will cause voltage issues

I do not have UDP's.

I fixed it - it was indeed the alternator going bad. I had a spare (actually I have two spares...one is the 8 rib off of Skwerl's old car)...but I used the 2008 spare I had laying around and ground the ears off and installed it.

It works great...idles at around 13.5 and is stable not only at idle but throughout RPM changes.

I might order that American Muscle rebuild kit and get the bad one back in good order in case this one goes bad. Or...bite the bullet and order an Innovators West Balancer and go 8 rib.

I would also need a Roush 8 rib blower pulley - any idea who sells those for a single-belt system Roush TVS R2300?

 

[DiMora]

Alright, the alternator I installed in post #23 on 9/5/2015 died this week. Battery is a nice Optima yellow-top beast (deep cycle capability) - so fortunately it did not harm my battery when it died. It was weird to watch the voltage drop off on my AeroForce interceptor as the battery lost voltage when the alternator died...first the traction control light turned on...then the ABS...then the battery idiot light...then I lost tach and speedo...then the car started to run rough and I pulled over. My wife brought me my Honda generator and my Optima battery charger - and I enjoyed some food at a local restaurant while it charged up, then I made it the last few miles home after my battery had a full charge.

So, deciding I'm tired of these crappy OEM Motorcraft 6G alternators, I installed a DOB bulletproof Denso unit I had bought a while back. That took some fabrication, as I ordered a rear Denso mount bracket from Roush that holds the rear end of the alternator to the supercharger's intake manifold...but the bracket did not match the orientation of the DOB alternator...or the OTHER DOB Denso alternator that I have (off of Skwerl's wrecked Bullitt), so I had to fabricate / weld up a modified bracket. Got that done, got it painted, installed...and I'm back in business.

However...here are my voltages read off my Aeroforce Interceptor (OBD-II plug):

Idling: 12.0-12.6
Cruising: 12.6-13.1

IAT's are around 127

Does that seem normal? (Voltage seems a bit low to me). Perhaps I should datalog voltages with my SCT....

Edit...I saw Bruce posted 13.3 is reasonable when it is hot out...I guess I'm close at 13.1 to that.

 

[Pentalab]

I'm reading 14.4 vdc on my aeroforce gauges, idle or cruise, or wot....... yet am reading 14.751 vdc with my calibrated Fluke 87 DVM.... with probes stuffed into the tops of the battery terminals. The aeroforce gauges ( all of em on A pillar) read .35 vdc low. I also used a megabuck HP lab style DVM on battery posts..and also got 14.748 vdc.

2 weeks ago, my 2011 Fusion would not start. Jump started the Fusion...and read 14.1 at idle... with fluke 87a with probes into battery posts.

Battery in mustang reads 12.5 with eng off overnight. New battery in Fusion reads 12.2 vdc... with eng off overnight.

The above readings were 2 weeks ago....and since I had the hood open on both cars , facing each other, and test gear out, took readings on both vehicles.

Try using a dvm, with probes into battery terminals. I suspect your aeroforce gauges may be receiving a correct reading, but a V drop is taking place some where in the wiring. Use the same dvm..and take readings in several places... like any 12 vdc aux jacks in cabin..... output of alternator etc.

While ur at it... switch DVM to read AC Volts....and then you can read any ac ripple. I'm seeing <20 millvolts....at idle. If u read sky high ac ripple, 1 or more diodes have shorted inside the alternator. (6 in total...since the alternator is 3 phase).

The fluke DVM's read AC.... and block the dc component since they use block caps in each test lead... internal to dvm. My B+K DVM does not have block caps, so it reads 14.75 vdc... when switched to AC V mode....so can't be used to read ac ripple.

 

[1950StangJump$]

Alright, the alternator I installed in post #23 on 9/5/2015 died this week. Battery is a nice Optima yellow-top beast (deep cycle capability) - so fortunately it did not harm my battery when it died. It was weird to watch the voltage drop off on my AeroForce interceptor as the battery lost voltage when the alternator died...first the traction control light turned on...then the ABS...then the battery idiot light...then I lost tach and speedo...then the car started to run rough and I pulled over. My wife brought me my Honda generator and my Optima battery charger - and I enjoyed some food at a local restaurant while it charged up, then I made it the last few miles home after my battery had a full charge.

So, deciding I'm tired of these crappy OEM Motorcraft 6G alternators, I installed a DOB bulletproof Denso unit I had bought a while back. That took some fabrication, as I ordered a rear Denso mount bracket from Roush that holds the rear end of the alternator to the supercharger's intake manifold...but the bracket did not match the orientation of the DOB alternator...or the OTHER DOB Denso alternator that I have (off of Skwerl's wrecked Bullitt), so I had to fabricate / weld up a modified bracket. Got that done, got it painted, installed...and I'm back in business.

However...here are my voltages read off my Aeroforce Interceptor (OBD-II plug):

Idling: 12.0-12.6
Cruising: 12.6-13.1

IAT's are around 127

Does that seem normal? (Voltage seems a bit low to me). Perhaps I should datalog voltages with my SCT....

Edit...I saw Bruce posted 13.3 is reasonable when it is hot out...I guess I'm close at 13.1 to that.

Sorry, just saw this. I also have the Aeroforce.

Because I have the KB, I couldn't do the DOB option (won't fit). So, I went with the 200 amp PA Performance alternator. I upgraded last summer because the stock alternator was fluctuating wildly, and because I put in a dual fan HE that allegedly pulls near 30 amps all by itself.

When first starting the car, the Aeroforce reads around 14.0. If it's cold outside, it might read 14.2 or 14.3. This reading is very temperature dependent.

As the car is driven, particularly in heat, it falls to the 13.7-13.9 range. Reading up on the subject, I think we are seeing resistance build in the wiring from heat that skews the computer measurement of the volts in some way especially through the OBD-II; I don't believe I am seeing actual system voltage drop . . . at least in any material way. I can be running the A/C, both HE fans, the IC pump (obviously), the radiator fan, blasting music, and have all lights on . . . the car doesn't show the slightest hiccup to indicate voltage concerns. The voltage reading just plain gets lower as under-hood temps climb; what I have sucking power doesn't seem to matter beyond the normal temporary drop in voltage readings when you first click an item on.

For what its worth, when I talked with DOB last summer, the guy swore the fluctuations were a characteristic of the 6G alternators, and his wouldn't do that. Well, sounds like it does (at least for you).

 

[DiMora]

I put a multi-meter on it. My Aeroforce appears to read .2 V low. I'm at 13.2-14.0 at idle if I probe my right front ground bolt and fuse box power points (my battery is in the trunk).

AC voltage is showing .8 mV so it looks like my diodes are fine.

Per Jason/DOB's recommendation, I'll be ditching my Optima yellow-top and trying an Interstate Battery to see if it performs better (Perhaps my Optima is crapping out on me and causing a voltage-suck)

 

[Juice]

Put the multimeter on the battery and compare readings to the OBD port output (what the PCM thinks the voltage should be.
This test will tell you if there is a voltage drop in the wiring.

I agree, seems a little low. I would be ok with 13 at idle and close to 14 running.

 

[DiMora]

Put the multimeter on the battery and compare readings to the OBD port output (what the PCM thinks the voltage should be.
This test will tell you if there is a voltage drop in the wiring.

I agree, seems a little low. I would be ok with 13 at idle and close to 14 running.

I did; it (AeroForce) reads .2V lower than actual voltage.

 

[Juice]

0.2 v difference is negligible for voltage drop for a trunk mounted battery.

 

[DiMora]

Another failure!

Either my DOB bulletproof Denso alternator died and Skwerl’s old alternator is no good, or my Optima died and killed the DOB, or I have bigger issues.

So far…I pulled the DOB bulletproof Denso and put in a brand-new Interstate MTZ-65 AGM beast. I installed Skwerl’s old alternator which I’ve never tried…and I have no alternator output. UGH!!!

I suppose Skwerl’s old alternator could be bad but the odds are not good.

I’m interested to see how my DOB alternator tests out.

I have checked the one 10A alternator fuse and all the wiring. Everything looks well connected.

More to follow.

 

[DieHarder]

Check your connections and grounds. Another test you can perform is to run another ground from the ground on the passenger strut tower and connect the other end to a mounting bolt on the alternator. I was having similar issues and extra ground solved the charging issue.

 

[DiMora]

Check your connections and grounds. Another test you can perform is to run another ground from the ground on the passenger strut tower and connect the other end to a mounting bolt on the alternator. I was having similar issues and extra ground solved the charging issue.

I am going to get the car on ramps and check the engine block ground. If it is good I will try your idea and report back what happens.

 

[DiMora]

Passenger side engine block ground checks good. Removed it, cleaned it up, and re-installed it with some dielectric grease to prevent any corrosion. It looked really good. I also tried using jumper cables to directly ground the alternator to the passenger side strut tower ground point. Voltage still 11.8. Put voltmeter right on alternator output bold...still 11.8.

Also checked both ends of alternator 3-wire harness and cleaned both plugs. Verified all three wires are good, cleaned both ends real good with CAIG electrical connector cleaner.

Double checked alternator fuse in under hood fuse box...replaced it to be sure it's not a bad fuse.

Checked trunk ground cable...it's rock solid (my battery is in my trunk) Checked all positive wires...particularily the alternator to (+) distribution block I run...all connections are good. Even if that cable was bad, I should have 13.4 volts or more at the alternator output.

So...either this alternator is bad - or I have bigger voltage control issues or a bad wire in a wiring harness...like perhaps in the wires in the car's main harness that connect to the alternator harness.

My next step is to get an alternator that I KNOW is good and see what happens. Might go buy a Denso from a 2010 while I wait for my DOB "bulletproof" to be diagnosed and returned to me if it needs repaired.

 

[DiMora]

Ordered a PA Performance upgraded alternator charge cable from AM last night (went with a GT500 length one)...I'm going to replace the existing one Roush provided that has the integrated fusible link in it just to eliminate a possibility that something is wrong there. The new one will be 4AWG - and it has an integrated 200 amp in-line fuse.

 

[Pentalab]

Ordered a PA Performance upgraded alternator charge cable from AM last night (went with a GT500 length one)...I'm going to replace the existing one Roush provided that has the integrated fusible link in it just to eliminate a possibility that something is wrong there. The new one will be 4AWG - and it has an integrated 200 amp in-line fuse.

If u measure just 11.8 vdc right across the alternator output, the problem is the alternator. When measuring the output of the alternator, you could also disconnect the positive of the battery terminal. You could also measure any V drop across any fuse, or fusible link.

I measure 14.75 Vdc directly across my battery terminals, using a calibrated fluke 87 dvm. My aeroforce gaugeS however, only read 14.4 vdc.

Unless 4 ga wire has some sky high insulation temp rating, it won't handle 200 amps CCS.

 

[DieHarder]

Regarding the grounds try connecting both ends of the battery cable to two different grounds on the alternator and body. The clips are going to give you a semi-decent ground. My fix involved using an additional 4 gauge wire w/eyelets soldered on both ends that I bolted to the strut tower at one end and the other to a mounting bolt on the alternator.

Since your cable length is much longer than normal (+8 ft) I'd be concerned with the voltage drop (if only .2v that's obviously not the problem). You should see something north of 13.5v output if your alternator and grounds are good. I think I currently run around 13.7v with my DOB. Not great, but does the job.

Another issue that crops up now and then are the cables themselves and especially the fusible link suffering from corrosion. Would be worth your while to check connectivity of all major cables end-to-end (should see less than 1/10 ohm for all grounds) and no more than .1-.2v drop on any power cable except in your case those longer cables are likely going to drop more voltage.

The only place I'd trust to tell me if my alternator was good is an alternator shop. Everyone else is only guessing. Every auto store alternator tester said my DOB was bad. The Alternator shop said it was good. Guess what, it was good. My problem was bad grounds.

If the alternator checks good and symptoms persist might be worthwhile to take it in for a systems check to ensure the PCM control signals are working properly. Though in my case they still didn't figure out that my grounds were floating (due to corrosion). Finally figured it out myself. Cleaned every ground I could find/get to and added a new one. Problem solved.

 

[DieHarder]

Correction....Regarding the grounds try connecting both ends of the battery cable (meant battery jumper cables) to two different grounds on the alternator and body. The clips are going to give you a semi-decent ground. My fix involved using an additional 4 gauge wire w/eyelets soldered on both ends that I bolted to the strut tower at one end and the other to a mounting bolt on the alternator.

Since your cable length is much longer than normal (+8 ft) I'd be concerned with the voltage drop (if only .2v that's obviously not the problem). You should see something north of 13.5v output if your alternator and grounds are good. I think I currently run around 13.7v with my DOB. Not great, but does the job.

Another issue that crops up now and then are the cables themselves and especially the fusible link suffering from corrosion. Would be worth your while to check connectivity of all major cables end-to-end (should see less than 1/10 ohm for all grounds) and no more than .1-.2v drop on any power cable except in your case those longer cables are likely going to drop more voltage.

The only place I'd trust to tell me if my alternator was good is an alternator shop. Everyone else is only guessing. Every auto store alternator tester said my DOB was bad. The Alternator shop said it was good. Guess what, it was good. My problem was bad grounds.

If the alternator checks good and symptoms persist might be worthwhile to take it in for a systems check to ensure the PCM control signals are working properly. Though in my case they still didn't figure out that my grounds were floating (due to corrosion). Finally figured it out myself. Cleaned every ground I could find/get to and added a new one. Problem solved.

 

[Juice]

Is your battery fully charged? 12.6v or better with cables disconnected, car off obviously. lol

If the battery is 50% or better discharged, but starts the car, measuring voltage is just pissing in the wind.

 

[DiMora]

If u measure just 11.8 vdc right across the alternator output, the problem is the alternator. When measuring the output of the alternator, you could also disconnect the positive of the battery terminal. You could also measure any V drop across any fuse, or fusible link.

I measure 14.75 Vdc directly across my battery terminals, using a calibrated fluke 87 dvm. My aeroforce gaugeS however, only read 14.4 vdc.

Unless 4 ga wire has some sky high insulation temp rating, it won't handle 200 amps CCS.

Trunk battery to power distribution block is 2 AWG. Alternator max output is 150 (2010 OEM Denso) or 160 (DOB) and will use the 4 AWG PA Performance alternator cable and in-line fuse.