battery gauge – what should it typcally read?

What should the volts gauge be assuming the battery and alternator are in good shape? Constant dead center? Mine was reading just under half way, would occasionally dip to four or three pips from empty but bounce back up again. It went so low as to prompt a warning light. The previous owner told me the alternator was new, battery old so I replaced the battery. The reading is more stable but it never goes higher than halfway and still occasionally dips to one or two pips below that (regardless of draw from lights, radio, windows etc). Is that normal?

Any pointers very much appreciated.

Ben

I Have 3 90s and all read in the center. Bill

That's for your reply Bill. It never fluctuates?

13.8 to 14.2 or so when running .

On 90 & 91 exactly halfway on the circular graph is nominal reading.

On 88 & 89 with a good alternator should be around 14.5-14.7 volts at idle and normal load as the setpoint on the alternator voltage regulator is generally around 14.6 volts. A marginal regulator or a heavy load will pull that number down. I just replaced a failed alternator on my nice 88, it now reads 14.7 on the nose at idle with no outside lights, cooling fans and blower motor on.

You may want to verify the new (likely a rebuilt) alternator is working right. Rebuilt alternators have one of the highest failure rates of any part I have purchased multiple times.

KDirk

Is the alternator a small frame (plug wires an fit underneath the alternator) or the large frame (won't). I used to replace a small frame about once a year but onlt rebuilt a large frame once. This the small is a CS130 and large a CS144.

Stock alternator for a Reatta is an early design cs144. Have that on all 4 of mine and a late design on the Deville. The CS130 is garbage IMO. Not nearly the service life of a CS144 and was done mostly for cost cutting (of course). The 144 can also be built out as a high output (200A) if desired by upgrading the rectifier and even more with a stator and rotor upgrade using an external bridge rectifier.

KDirk

Nice thing about a GM alternator is that if the ears are in the "wrong" place and won't fit all one has to do is remove the 4 long bolts and rotate the front to fit our cars. I took one off a Park Avenue, and rotated the head and installed. Works great...

Stock alternator for a Reatta is an early design cs144.

Correct but 25 years out almost anything could be there, they are interchangable. (why I asked about the plug wires)

True enough. The CS130 will fit but I don't suggest using one due to known shortcomings in the design.

KDirk

Just got back from Gibson's after pulling some parts for a friend. They just got another '90 Riv in so I tested and pulled both the IPC and the alternator. Mine had been making some front bearing noise and this one looked like brand new so I grabbed it. The IPC I grabbed because it was there and cheap and tested good.

After installing it in my Reatta and reconnecting the battery cables, I turned on the car and got a message in the odometer line. It was the photocell value. This was on the Black '89.

Isn't the '89 IPC different than the '90?

Yes but we were getting off track anyhow by talking about messages that "pop up" after connecting the battery cables. I can delete my message if it makes you feel better. Just let me know...