Alternator questions

I had this post all written and was checking it and hit the wrong button and my long-winded description vanished into electron heaven. So I will give a more abbreviated version this time.

I recently have had starting issues both after driving for a fair distance with the AC on and also after leaving the car sit for as short as a day. I have proven it is not the starter motor as a quick charge gets it going. Battery is large and new and it does not fit the pattern. I checked for amp drain while idle which I had 18 months ago when I bought the car and I do not have that problem now. I checked the charging and here is where the issue seems to be. I get about 12.8 V at idle and 13.6V at 2000 RPM or higher. When I bought the car I checked and had 13.6 at idle and 14+ at 1500 RPM or higher. So I suspect one or both alternators are weak or not functioning.

Here are my questions:
1. What is best procedure to check each alternator? Remove one belt? Remove all wires from one unit? I know it is possible to ruin a good alternator by pulling wires while motor is running but I think there should be a way to check each one with motor running.

2. Let's say I identify one bad alternator, what is the origin of these units? Are both identical? Does anyone know a shop to rebuild them in a timely manner in the Northeast US? Can they be bought outright at a reasonable price? If they are of common origin, I have a local shop that does good work and I will tell him it is from a Fiat to keep the cost down.

I look forward to some quick replies as I want to sort out this weekend because I have an F-club event the following weekend.
Ken

 

I have still not confirmed for sure one or both alternators have failed. In advance of the weekend, I did some price checking. Local F-dealer has one in stock new for $1092. Eurospares had a new for 415 Lb Sterling or 200 "good used". So I have fall back positions if replacement is required. Local dealer said units are Bosch and most people have them rebuilt. Other than the pulley I might try to find a match and buy a new Bosch and swap the pulley.

This weekend I will sort out the need.
Ken

 

I have tested system pretty thoroughly including with the top alternator removed. At idle I get ~13.5 V and it only goes to 13.8 V at 2000 RPM or higher. This is with no or low load. When I bought the car the same test gave 13.5V and 14.0V, so alternators appear a bit weak. I applied load, fans and A/C and voltage at battery is a bit lower, maybe 13.5 at 2000 RPM. I removed the top alternator and retested and the numbers are about 0.2 V lower. It appears as long as I do not run A/C lights and such with the car at idle for a long time, I should not run the battery down; that is just a stop gap measure. Both charging lights on the speed are out whenever the engine is running.

Having removed one alternator, I see that a rebuild is quite easy, since all of the components that usually fail are bolted on the outside of the alternator. My plan will be to find a good shop that rebuilds Bosch units and get him to test / rebuild the top one first. The lower one can be removed without too much hassle since a PO ground one side of the head of the bolt off to clear the steering component; I had it out when I replace the belts.
Ken

 

If the alternator is in the car, what is the best way to put a load on it? Is there a test box for that? IF so I think I can borrow one from my local parts place. I know I can turn on A/C, lights etc. and have ammeter in the power line from the alternator.

I will be calling local shops to see who has best story about testing and repairing Bosch alternators. I will likely leave it to them.
Ken

 

Mark
I think I am convinced that I am just not getting enough amps out of the two alternators. The battery is really dead when it will not spin the motor, with a quick charge the car starts fine.

I have a shop to check the alternator now, but it will be 2-3 weeks before I get it to him. I have a backup plan for upcoming trips!
Lem

 

I pulled the alternator and brought it to a garage I just found that does electrical work. He pulled unit apart and tested all of the components that he could test without having a bench to spin the unit. We concluded the easiest thing to do was to replace the voltage regulator / bushes unit. It is Bosch Part # 1-197-311-028 and cost only $48. It takes about 5 minutes to swap in the new unit; it is external and held in by two small bolts.

I retested same conditions of load and voltage (unable to measure amps) and it gives 0.4-0.6 V higher reading at the same load conditions. These readings are now the same as when I bought the car 2 years ago (almost my second anniversary).

So I think I have solve my problem. Over the winter I may just buy a second regulator unit and swap out the lower one. If I have enough space I may not even have to remove the alternator from the car!?
Ken