My Bronco (302-E4OD) shows to be putting out 15V on the dash ammeter. I just finished putting an engine in it and getting it back on the road.

I seem to remember that it should be showing about 13V in normal operation at highway speeds.

I have not checked all of the electrical grounds yet but I will get to that when I get it out of the shop where they are recharging the AC.

I plan to check for rust at ground straps - clean and re-attach, then check for rust spots on the voltage regulator connector - clean and re-attach.

What else am I missing? The battery is brand new and shows 12.6V with engine off. I haven't checked low idle or fast idle voltages yet but plan to do that too.

The battery cables are original and are clean but they have had a little corrosion on the bolts over the years. The mating surfaces are fresh and clean though. I'm not sure they fit the posts as tightly as a new one would. Possibly time to replace the cables?

I think the voltage regulator gets it's ground at one of the mount points so I will remove it and check to be sure it is clean, etc.

I don't think the 15V ammeter reading at 65 mph is a good thing and need to solve this before I go on vacation in this Bronco in a week.

Thanks in advance for your ideas.

 

I would start by replacing both battery cables especially if they are original hardware. Cables are cheap, get some good quality 2gauge or 1gauge cable. the alt may also be failing as it has an internal regulator. Its probably time for a 3g altenator upgrade so you dont burn up.

 

Verify that the gauge is giving you the correct reading by taking one yourself with a decent multi-meter. I have NEVER trusted the pseudo-voltage gauge in mine because it is NEVER accurate. How do I know? I just mentioned that.

 

Thanks for the info and sorry for the delayed reply. I have been searching posts on several forums all day to make sure I can get the right parts ordered.

I am looking at the 130A alternator from RJM Injection, a 1 7/8" pulley, an alternator harness, an alternator charge kit, and a headlight harness. I need to build battery cables so I have to look at how long they have to be, a big unknown for me right now. Any tips are appreciated especially if they help me order the right cables.

I've also been looking at the 170A alternator at Bronco Graveyard which claims to be a 1-wire set-up.

The questions that I have for anyone who is familiar with these products are:

What else would I need to order from RJM to end up with complete replacement of alternator and battery cables?

If I go with the Graveyard it claims to use the stock connectors, the 2G connectors in my case since that is what I am upgrading from. I don't see how this can be right. Has anyone used one of these?

I think from the description that the Graveyard alternator uses a 1 7/8 pulley too. One advantage of the Graveyard alternator (acc. to them) is that it is not necessary to modify the bracket to make the alternator fit. I have found that I will need to do a little modding if I use the alternator from RJM. I suspect that the Graveyard may not be right so if anyone has anything to add here I would appreciate the benefit of your experience with the product.

It has been mentioned that I may need a shorter than stock size serpentine belt if I use the smaller 1 7/8 pulley. Does anyone have any experience with this? Can you give a part number for the belt that I will need if I do need a different one?

Sorry but my brain is sluggish. I think I have been reading all day and now my brain is full.

Thanks to everyone for looking.

 

Thanks for the response. I already verified the voltage at the battery with my meter since, like you I have developed a distrust of dumb gauges especially in vehicles with over 270K miles on them. Everything eventually wears out so I expect the same fate for my dash instruments.

The meter shows 14.6V when the engine is running.

When I kill the engine after driving for 10 or 15 minutes the battery voltage is 13.7V. After overnight sitting it settles to 12.6V which seems to be about half a volt from a full charge I think.

The battery is new. It did sit for a while before I got around to the shift kit so maybe I need to charge it up to full charge before running again. Does any of this sound out of spec?

Thanks for the reply.

 

Skip that 170A alternator, with the stock belt you won't see any more amperage than 140, as it's stated in the RJM site (and throughly explained).

 

Thanks Encho, Kemicalburns, and Greystreak92. I've been all over the RJM site, FordFuelInjection, FullSizeBronco, FordTruckEnthusiast, etc. and have read everything I could find. There is a lot of great information out there and much of it is laid out so that a newbie can find an answer without too much trouble. Major props to all who have contributed.

I've put in an order from RJM for the 3G 160A alternator and other parts to upgrade my current stock 2G setup. I also added a few parts from other sources to make installation easier (hopefully) and give a more professional look to the end result. I can post pics of the upgrades and additional parts after I install if anyone is interested.

To illustrate how tired I was when making the original post I kept calling the alternator that I planned to buy from RJM a 130A alternator when I was really trying to compare RJM's 160A 3G with the Graveyard's 170A 3G upgrade. I just wasn't taking very good mental notes.

The output is only 10A different but the Graveyard write-up claims that there is no modification of the bracket necessary to use their 170A alternator on a 92 Bronco while the RJM write-up shows the need to remove a little from the stock bracket to install their 160A alternator.

I would obviously like to make this as simple as possible when I upgrade so modding the bracket is something I would tend to avoid but at the end of the day I decided that the Graveyard 3G alternator had to use the same case as the RJM alternator but with a different rectifier to produce 170A instead of 160A. Therefore I decided that I will need to mod the bracket no matter where I get the alternator and since RJM also offered the improved harness, etc. I went with them.

One thing to note here about RJM's site that others have also posted about. If you have a question and use their contact link to attempt to get an answer by email you are probably wasting your time but not much of theirs. I asked a couple of questions by their direct email, included a phone number and have so far not received a reply. In spite of this I did end up calling them directly before ordering to clarify what parts they had on hand, which parts I would need, etc. and got a live person who answered all my questions. After that I was able to finalize my order.

Not necessarily good customer service. If they are too busy to answer emails then they should remove the contact link from their site - trim the deadwood if you will - and just force the phone contact. Don't try to look like you're up to speed with the technology if you're really still stuck in 1985.

 

Your results seem to be within spec. A good alternator will put out 14.7 volts. Voltage over this may be a problem as the internal regulator shoul keep it from overcharginging the battery. Hope this helps.

 

Menesesjesse, I appreciate the information. After reading a lot of material I had come to the same conclusion that the reading over 14 volts was not a real problem. I decided to do the alternator upgrade now anyway since we are in the process of bringing the old Bronco up to speed on everything else. We're upgrading just about everything on it so maybe it can go another 270K miles.

It just made sense to get a new alternator, get rid of the old cables and set up a couple more power points to drive the gadgets that the kids will be taking for entertainment as we pass through some of the most beautiful scenery in the US. Oh well, at least one of us will be looking out the window all the time.

I am still chasing a potential short in the system. I may have to start a new thread for that one if I can't solve it soon. Thanks for your input. I appreciate it.