88 idi voltage problems

[troy]

I recently had my alternator rebuilt on my 88 f350 n/a idi, and my voltage gauge was still at 9v so I replaced the external regulator. This brought it up to about 13.7v at idle. When driving with the headlights on, the gauge drops slightly but once I turn the a/c on with the blower on Hi it drops to the red line on 8v even while going down the highway with the engine at 2000rpm.
Could this be bad batteries draining too fast for the alternator to charge them? Or something else?

 

[79jasper]

I would say time for a 3g swap.

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[icanfixall]

Your rebuilt alternator is failing. Take it back. The oem alternators are low output but they can handle the electrical load the oem systems put on them. All our batteries do is store enough amps the start the engine. We do not depend on a battery to drive our trucks or cars.

 

[BioFarmer93]

Swap in a 200A 3G, and you can run the whole island with it.. Before you do that though, take a weekend and go through the entire underhood electrical system- disconnect, inspect, clean, NO-ALOX, and reconnect all of the connections, including grounds. Unless you have been on-point recently with the electricals, I guarantee you'll get a couple of volts back due to lowered resistance.

 

[troy]

I took the alternator back and they said a diode had burnt out inside the alternator . i recently checked out the voltage after I upgraded the charge cable from the alternator to the battery to an 8 gauge cable ..its now 14.48v at idle and 13.36v with the fan on Hi the headlights and the wipers running. That should be sufficient enough but that's on a volt meter . on the dash it shows 8v and having all those things running makes the oil press and temp gauge go up for no reason... I don't really understand this

 

[troy]

Aside from that ..I would like to upgrade my alternator just to do it and not have to worry. Finding one on my part is a little tricky. I've searched for one before but no luck. The alternator I have now has the dual belt pully and the wires plug in on the top..when I search for H/O alternators I don't see one like mine ..would I have to order one with the same wiring harness and switch the pullies or have any of you had luck with this?

 

[BioFarmer93]

My 3G accepted the double pulley just fine.. I put the serpentine style pulley on the old one to take it back to the parts store fore the core return.

 

[troy]

My 3G accepted the double pulley just fine.. I put the serpentine style pulley on the old one to take it back to the parts store fore the core return.

Did you have to change the wiring due to an internal regulator?

 

[troy]

I also have read that large case 170 amp alternators can be taken off late 90s Taurus's . and will fit fine with a little wiring modification though .I was thinking of buying one from Napa and going from there

 

[BioFarmer93]

Did you have to change the wiring due to an internal regulator?

Yes, but it wasn't too bad. I kept the multi wire plug to the old regulator and just used one hole in it for the single wire (and I can't remember which one now) that had to stay. I think it was the "ON" wire from ignition, but not sure. After I verified that all worked as it should I just taped it up and called it good.

 

[BioFarmer93]

I also have read that large case 170 amp alternators can be taken off late 90s Taurus's . and will fit fine with a little wiring modification though .I was thinking of buying one from Napa and going from there

Yes they will, also being 3G's.. The wiring mods consist of eliminating most of the old voltage regulator wires and making a new, heavier charging cable to the battery or solenoid, depending who's method you like best.

 

[icanfixall]

Well so it was a bad diode..... Glad it was a simple R&R job. Nice to be able to watch the gauge and not worry.

 

[troy]

Well so it was a bad diode..... Glad it was a simple R&R job. Nice to be able to watch the gauge and not worry.

Yeah the voltage looks great on a multi meter but on the dash gauge it shows low voltage ..but then again all the gauges on my dash are screwy . the mph gauge bounces. And the rpm gauge doesn't come on until like 5 mins after a cold start . the fuel gauge goes way past full and turning on the headlights makes all the gauges move

 

[OldIron82]

I had almost the exact same problem. Bought a "new" rebuild. Junk out of the box. Took it back and got another new rebuild. This one charges, but it is slow to move the gauge. I still need to put a volt meter on the batteries and see exactly what is going on but for now the gauge never gets higher than 13 volts. I was always told 13.8 to 14.2. We all know how factory gauges can be.

 

[troy]

I had almost the exact same problem. Bought a "new" rebuild. Junk out of the box. Took it back and got another new rebuild. This one charges, but it is slow to move the gauge. I still need to put a volt meter on the batteries and see exactly what is going on but for now the gauge never gets higher than 13 volts. I was always told 13.8 to 14.2. We all know how factory gauges can be.

Yeah the factory gauges must be getting a little worn by now after 27 years ...I'm thinking of getting the 3 gauged pillar pod mount and putting an EGT, a voltage, and oil temp gauges up there