Is it possible to adjust a Ford alt's regulator?

[cgrey8]

I have a 97 Explorer V8 motor in my 89 Ranger. Ever since it's been running, I've noticed that my voltage isn't nearly as high as it used to be with the Ranger's alternator. Using my TwEECer (ECM tuner & datalogger), I can see that my voltage in the morning is in the mid to low 13s and when the engine warms up, the voltage drops to the high 12s. Because it is maintaining higher than the battery, I'm not experiencing any charging problems, but I'd still like it to charge at a higher voltage...closer to 14.4v so my stereo amp will run at max output.

I don't know if this is a product of using a different generation motor (and ultimately alternator) on my truck or if the problem is simply the alternator. I know when I worked at an auto shop that some alternators just won't put out as much voltage as others will, presumably because of regulator adjustments. If that's all it is, then I may be just a screwdriver turn away from getting the voltage output I'm looking for, but I thought I'd run it by the pros 1st before I went prodding with a screwdriver.

[awesomebill]

You can not adjust with a screwdriver. This is built into the int/voltage regulator. You could trick the 12 volt read wire with a resistor to make it read lower voltage and would cause the alternator to get the 14.5-15 volt you wish. You could also buy an aftermarket regulator from an alternator shop or even on line.

[cgrey8]

The aftermarket regulator sounds interesting. Would it replace the existing one or would it interface with the internal regulator and modulate voltage out to it in order to get the output voltage it is looking for?

The resistor idea sounds compelling too. Any recommendations on resistance (in ohms) and watt rating just to get me in the ballpark? Worst case scenario, I install a rhiostat to varry the resistance to get the output voltage I'm looking for.

[EthylCat]

I would do all of my voltage readings at the battery or the output terminal of the alternator, but most likely both. Don't rely on processed data if you do not have to. I assume since you have that scan tool you also have a simple voltmeter? The first step to any charging system diagnosis is to verify that you have a good battery( Read LOAD TEST!). If the battery voltage is below 12.4 volts at the begining of you diagnosis you won't get an accurate test result, charge it before doing the load test.Once that is established, perform a no-load test. This is simply the vehicle in park/neutral and all electrical loads off. Run the idle up to 1500-2000 and look at the voltage at the battery. It should be 13-15v. If it passes that test move on to a loaded test. Same running conditions except turn the blower on high and the high beams on to load the system. Recheck your voltage, it should be 12.5-14 volts or so. This checks the regulators ability to do its' job. If the voltage is lower than 12.5, find out which wire going to the alternator is the voltage sense wire from the battery and see if it is reading within .5v of what the battery is seeing. If ok, you may have a bad regulator. The last test is to perform an output check. Load the battery down until it reads 12.0v and check the amperage output. It should be within 80% of manufacturers spec. Engine running at high idle still. There are also voltage drop tests that you can do on the alternator charge output cable and ground circuits, and AC voltage output tests but you may not have to get that deep into it. Good Luck!

[cgrey8]

I haven't taken these measurements at the battery, but for the most part I can tell you the battery is around 12.1v with no load and the engine off. With the engine on and cold, the alternator raises voltage to around 13.3v. After the engine warms up, this drops to around 12.9-13.0v. If I load the system up by turning on my blower motor and all lights (I have about 600w worth of lights), the voltage does drop momentarily but returns to around 12.7. The regulator appears to be able to adjust and maintain the voltage it is targetting, it's target is just lower than I'd like.

I don't have a high-amp gauge and loader to test the output of the alternator with. When I worked at the auto center, I did. It was a nice setup with a loader dial good up to 1000amps, amp meter and volt meter all in one device. I could put the ampere pickup on the alternator's load wire and tell you exaclty how much current the alternator was putting out and the voltage at that load. Unfortunately that place closed shortly after I quit so I don't have any friendly connections otherwise I'd cash in a favor or two.

Based on what you just described, it sounds like my regulator is just internally adjusted low, but still within spec. If alternators weren't so dern expensive, I'd go get another one. But since it isn't causing any problems for me, it's just not giving me the voltage I'd like to see, I can't justify it. The resistor idea sounds much more appealing...and something relatively easy to implement.

[EthylCat]

I know that you have a lot of extra load on the system, but if you drive that thing around for a day or two with out running it all and the open circuit voltage on the battery before start up is still below 12.4v I would think that you had a bad battery that is not holding charge, or possibly too high of a parasitic draw with the key off drawing it down as it sits. To check for a draw, unhook the negative battery cable and install your voltmeter(set up to read amps) into the circuit to complete the path back to the battery. Make sure that you are fused to at least 10 amps in case there is a problem. Actually, in your case I would use a jumper wire to complete the circuit first and then hook up your meter parallel to the jumper to prevent all of your accessories from causing a momentary surge and blowing your fuse. Once your meter is hooked up, remove the jumper wire. For normal vehicles, the amp draw should be no more than 50mA (milli-amps/.050A). You might see a litttle more with your extra equipment though. I would not want to see any more than 100mA at the very most and even that may be too much. If it is higher than that you need to start pulling fuses until the drop becomes acceptable. That is the component/circuit that is bad or needs to be rewired. Keep me posted!

[cgrey8]

The battery is relatively new (less than 2 years old) and it wasn't the el Cheapo on the rack either. It cranks the truck fine and with the exception of some corrosion on the terminals, I've never had it not start the truck. Recently, the truck sat at the airport for 2.5 weeks. That was the longest the truck has sat without being turned over since I put it together and it fired right up. So I don't think there is a bad parasitic draw.

Note all the voltages I quoted are as they were logged by the ECM using my datalogger. Again, those were not voltages measured at the polls. I haven't done that test yet. That being said, it is possible the voltage at the polls would be a .1 or .2 higher. I'll go back and check the voltage at the polls and see if it is higher. I'll TRY to remind myself to do that tonight.

[EthylCat]

Do you have underdrive pulleys on that vehicle?

[cgrey8]

No, it's all stock Explorer motor with no underdrive pulleys or anything like that. The low-voltage I'm witnessing happens regardless of whether I'm at idle or at cruising RPMs. In fact, idle voltage seems quite stable, just lower than I'd really like it to be.

The V6 that came factory in the Ranger was very suceptable to low voltage at idle. With only the blower motor on, I could watch the meter move as I revved the engine. In fact, the alternator was barely big enough to run all my lights on the truck. Even while cruising, I could turn on all the lights and the voltage would be just about where the battery voltage is. With the blower running full blast, the voltage dipped below the battery which basically meant I was discharging the battery. But this alternator barely moves my voltage gauge unless I have it heavily loaded at idle. I guess that's the difference between my 89 Ranger's 40A alternator an the 97 Explorer's 130A alternator.

[BT Motorsports]

Contact http://www.alternatorparts.com, they should be able to help in your quest.

Paul

[cgrey8]

Thanks for the reference, but I finally figured out what the problem was a few weeks ago, a ground wire had corroded off. I had the ground between the battery and the engine block solid using a heavy gauge stereo amplifier wire along with the stock heavy gauge wire that runs from the battery down to the frame. But Ford also puts a pigtail on the battery negative that attaches to a ground lug on the body. That pigtail had come off so I had a huge groundloop that ran from the body to the frame to the engine and battery. After landing that pigtail back to the ground lug on the body, my alternator voltages have been up where they are supposed to be.

Just another example of bad grounds causing problems.

[BT Motorsports]

Thanks for the update! We should all try to make a habit of posting the solution we find so everyone can benefit.

Paul

[cgrey8]

That was my fault.

I usually do that for the other forums I frequent. But, I'm relatively new to Speedtalk, and once this thread went dead, I kinda forgot all about it until you posted an update.