On my 1985 F150 5.0 EFI I have a charging issue. I am serving as a great example of spending money needlessly, and that had I followed some simple testing prior to the spending of money, I'd have money for a case of my favorite brew. So here it is.

I purchased a new alternator about 1 1/2 years ago. The voltage regulator was also replaced. About 1 week ago, I noticed that it wasn't charging. So I did some head scratching and decided to pull the alternator. I wanted to check to see if all connections were tight. They were, so I then checked the continuity of each wire. All was good there as well. After reconnecting the wires I installed the alternator hoping for the best. Still, it wasn't charging. What do you think I did? Yup. I spent money on a new alternator.

The new alternator arrived and I installed it. Still no charge. So I kicked myself and then bought a new voltage regulator that should arrive in a few days.

I emailed my old buddy, Vinny. Vinny emailed Gary's Taj Mahal (I am no stranger to that extensive and very useful document but too often forget about it). I reviewed the section: Charge & Power Distribution - ???Gary's Garagemahal.

Vinny asked me to do a resistance check with the new alternator. The reading was .2, so all was good.

I then checked for voltage on the wire that has a fuse link that comes from the battery terminal on the alternator. That wire tested just fine. We then checked voltage on some other wires that come into a plug that connects to the regulator. There was not detectable voltage in two of ht wires. This pointed to the voltage regulator as the likely culprit. Hopefully, that will arrive soon and things will work just fine.

My point is for those on this board that do the same thing I have done way too many times. Do some due diligence before spending money.

Thanks to Vinny and Gary's Taj Mahal for getting me through this!

 

We've all been there, done that, and didn't get the drinks. I'm betting that the regulator will do the trick. But, there is more troubleshooting you may be able to do.

If you haven't, try this test from the factory shop manual. First, is a jumper that you'll have to make or use alligator clips. In the first test you are using the voltage coming from the wiring to power the field of the alternator. If that works then the alternator and wiring are good and the regulator is bad. If that doesn't work then go to the second test. If that works then the wiring is bad and the alternator is good.

 

Thanks, Gary! Those are very good tests that I will do tomorrow. Again, thanks for the Taj Mahal! I have referred to it many times; will need to remember it for everything I do with my Ford.

 

Welcome. Happy to help. Let us know how it works out.

 

I certainly will!! Thanks again!!!

 

Steve, Do you have an Ammeter Gauge or an Idiot Light in your Dash? showing you if you are charging or not ?

EDIT: I'd say Light......

 

I have an idiot light. Would prefer to see the actually amps being charged.

 

Actually, I think I prefer the light. The ammeter works, but if you lose the alternator during a time when you aren't running a large accessory load, like the headlights or the heater or AC you probably won't notice the slight discharge on the ammeter. That happened to me.

And, if you upgrade to a 3G you would have to eliminate the ammeter as the shunt that supports it isn't up to the output of the 3G. But, the idiot light Cluster doesn't support a tach, so I've considered modifying a cluster to have both a tach and idiot lights.

 

Interesting. I found some updated instrument clusters that come equipped with an entire array of gauges. The gauges sit in a made to fit panel. Not sure of the complications but have consider getting one if I eventually customize the truck. http://classicdash.com/product/ford-truck-1980-1986/

Yesterday, I attempted the tests you recommended for the charging system. My issue was that I was to certain where to connect my voltmeter. I ran the jumper to the correct ports on the voltage regulator plug, had the positive probe on the BAT connector of the alternator and the negative probe was on the negative ground on the battery. I read 12.23 volts, but suspected I wasn't performing the tests as I should have. So I gave up, not knowing exactly where to connect the probes.

I will appreciate your guidance here.

 

Interesting dash. Didn't look, but do they make a radio bezel to match?

On the testing, you should put your voltmeter on the battery. But, that should be the same voltage as the BAT connector of the alternator, so your test should be accurate. And, if you jumpered it as shown then you have a problem that isn't the regulator. When does your new regulator come in?

 

I looked to see if they make a matching radio bezel. Didn't see any.

To be clear, I had the plug to the regulator disconnected from the regulator. I connected a jumper wire to the A and F ports. I then took the positive voltmeter probe and connected to the Bat on the alternator and the negative probe was to the negative terminal on the battery. Ignition switch was in the off position.

The regulator arrives today.

 

The test you ran should put the alternator in full-output mode. You can see here, from Page 12 of the 1981 EVTM, that jumpering Terminal A, which should be straight from the battery, to F will put full voltage to the field of the alternator. So if doing that didn't get the voltage to go up significantly then something else is wrong.

Did you rev the engine up to at least 1200 RPM? If not maybe you have enough load on the system to absorb the output of the alternator at idle. If you did, then check Terminal A to ensure you have battery voltage there.

 

I just wanted to know what electrical drawing to look at. There are two available in 85', one with light and one with gauge. But then I remembered you said 4 wires to regulator +ground, light has 4 wires +ground, and gauge has 3 wires +ground .....

 

Yup - The drawing right above.

 

I didn't rev the engine. In fact, the key was off and negative terminal to the battery was disconnected.