Alternator November 27, 2016, 02:24:05 pm Naturally, while repairing my clearance lights, I left all the lights on for a couple of hours! By the time I noticed, the battery had gone dead. I recharged it all night. This morning the battery showed 12.6 volts, so I started the coach. I then noticed that the alternator was supplying 18.6 volts. I'm pretty sure that is a bad thing? My questions are: is that a bad thing? If so, would it mean the voltage regulator isn't working properly and I need to replace the alternator? And finally, if I need to replace the alternator, what voltage is required for my 1991 E350 econoline with the 460 CIA Ford engine? Thanks a ton. The output is what I need. I.e. 80, 100.? Brand matter?
Re: Alternator Reply #1 – November 27, 2016, 02:56:01 pm Now I'm finding out that there may be a chance that my 1991 460 ( 7.5L) E350 Econoline may have an external voltage regulator. Wonder what the odds are?
Re: Alternator Reply #2 – November 27, 2016, 07:52:23 pm Seeing that there are several different alternators available, you need to see what is presently installed. The regulator will be internal or external, depending on the alternator.Later in the 1990s, the alternators became regulated by the engine's computer (ECM).High alternator voltage is normally a regulator problem or a poor electrical connection that causes the regulator to "see" a lower than actual voltage .Charge voltage should be between 13.2 and 14.5 volts, depending on the battery charge level, the load and the alternators' temperature. 1 Likes
Re: Alternator Reply #3 – November 28, 2016, 03:51:55 am Quote from: dollinsdale - November 27, 2016, 02:24:05 pm I then noticed that the alternator was supplying 18.6 volts. I'm pretty sure that is a bad thing?Is that measured at the battery? If not, then check at the battery isolator. If the voltage measured at the alternator terminal is more than a volt higher than at the chassis battery terminal, then the isolator is bad.Steve
Re: Alternator Reply #4 – November 29, 2016, 09:49:56 am Question?Are you using a digital cigarette lighter volt meter thing from camping world? They Lie.I had one and left it plugged in while traveling because of a 1991 Ford Amp meter showed little movement. Unfortunately the little digital thing lacks temperature compensation and after a day of driving it was indicating 17- 18 volts. My digital voltmeter indicated 14.5 volts. That little jewel led me astray. The first time, I drove from Tahoe to San Jose with the Regulator disconnected. In the end it cost me an un-necessary battery and regulator change. The second time it happened I checked with a digital Multi-meter. that Digital cigarette lighter volt meter thing is NO MORE!FYI My 1991 E 250 Coachman 19RB with High current side terminal Autolite alternator has an External Regulator.Rodney1988 26MB 1 Likes
Re: Alternator Reply #5 – December 01, 2016, 08:54:32 pm As it turns out, my '91 460 ford does have an alternator with an external regulator. I replaced the original motor craft regulator with a new motor craft one and it worked. The bad news was that a four year old napa was done in before the regulator problem was uncovered. Total battery plus regulator @ $150. Could have been worse. 1 Likes
Re: Alternator Reply #6 – December 04, 2016, 11:03:26 pm Oops, spoke too soon. So far I've replaced the battery, the external regulator and the 100 amp alternator. I'm still getting a very low reading from the alternator of 11.0. If I remove the negative cable connection at the battery, while the engine is running, it immediately shuts off. I think this means that there is no voltage coming from the alternator and that the engine is running solely off of the battery. I'm out of ideas. Could it have anything to do with the battery isolator? Has anyone had a battery isolator fail? If so, what are the symptoms of a failed isolator? Any other suggestions of what could be wrong?Be well and happy holidays. Dale from Downey.
Re: Alternator Reply #7 – December 05, 2016, 10:56:21 am I see you did as my Late Grandfather did to check the old Brushed Generators! That is a strong indicator that there is no DC output from the Alternator or generator. it is most likely in the Alternator and potentially the Isolator.Caution Notice: In the process below keep all hands, body parts, tools, and wires out of the way of the engines moving parts.With a volt meter you could check the voltages at the three posts of the isolator, referenced to ground. Engine off, key off.1. First measure both battery voltages. 2. Then go to the battery isolator You should measure starting Battery voltage on one side. 3. You should measure Coach battery voltage on the other side. 4. You should measure the alternator voltage on the center post. If there is an smaller Auxiliary post it is to run the GMC Delco Alternators, Ignore it on Fords. 5. Engine off, the center (Alternator) post should be 0 dc volts to ground. 6. Engine running. the center alternator post voltage should be a 0.5 to a few dc volts higher than the battery voltages. If the Engine running DC voltage at the center alternator post is 0 it is likely the alternator/ regulator system has failed. With the engine off, key off, if the center post voltage equals a battery voltage a diode(or similar) is shorted in the battery isolator.The second check, the battery response to starting. while resting the battery should be fully charged at 12.5 volts. When starting the battery circuit should maintain a minimum of 9.5 volts while starting. Upon starting the battery voltage should climb to the range of 13.5volts (Delco) to 14.5 volts (old ford relay regulators). You should be able to measure a similar response on the center alternator terminal of the battery isolator.If it looks like the alternator has failed, you could also have an open between the Regulator and Alternator, or no battery voltage from the key to the regulator. A shorted Noise Capacitor at the regulator. 1 Likes
Re: Alternator Reply #8 – December 05, 2016, 12:50:34 pm rodneyhelfrich. Are you saying that the noise capacitor at the regulator could be the culprit? Mine had a corroded connection which I corrected.
Re: Alternator Reply #9 – December 06, 2016, 10:15:24 am It has been 30 years since I played studied the circuit and I do not remember where the cap is connected. It is a noise filter for the radio. Chances that the capacitor is the problem is near NIL. Un plug the capacitor and see if the issues go away. You will hear more noise in the AM/FM Radio, when the engine is running. I would bet on the alternator being the culprit. Check the voltages at the center post of the Battery isolator with the engine running. The center post should be the same as the B+ ouput on the alternator, according to the on-line schematics i am finding.I am sorry if I confused you in your trouble shooting of your charging problem. 1 Likes
Re: Alternator Reply #10 – December 09, 2016, 03:46:35 pm In the final analysis. It was a faulty regulator connector that caused the low reading. Of course, the connector was impossible to find because it is an obsolete part. However Ford was able to find me one that I was able to make work. Everything is fine now. Reading 14 at start up and charging fine. New alternator, regulator, battery and connector. Cost @ $250. Peace of mind: priceless. 3 Likes
Re: Alternator Reply #11 – December 10, 2016, 07:05:42 pm Dale said, "New alternator, regulator, battery and connector. Cost @ $250. Peace of mind: priceless."...and the fact that you have the knowledge, experience, & willingness to tackle the job in the first place. Thx for sharing your journey--I feel smarter just for having read it, even if I don't really know where I've been or how I got there. Lynne 1 Likes
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