'90 Alternator upgrade from CS130 to CS144 = Need to add Resistor?
Some advise please -
I'm replacing the CS-130 alternator in my 1990 Coupe with a CS-144 unit (using a unit list for a 1996 Olds Aurora Northstar Engine).
Everything I've read indicates that the two style alternators are plug and play - no conversion rewiring is required.
Everything seems to fit mechanically w/o any problems. Even has the same pulley. As expected, I needed to mill the upper flange fitting - removing 4mm so that it is narrow enough to fit into the existing bracket.
However, I'm still confused / concerned about the need to add a 35 ohm 1/2 watt resistor to the existing wiring harness or not...
Is the CS144 truly plug and play when replacing a CS130 - or do I need to add a resistor?
I measured the resistance from the disconnected positive battery cable (with the ignition on) to the "L" treminal on the disconnected alternator wiring harness - and measured 14 ohms. So there is some resistance, but less than half of the "recommended" (min) 35 ohms and nowhere close to the (max) of 350 ohms.
I'm not sure if the "battery icon" on the DIC is technically considered an idiot light - but I keep getting hung up on the fact that if I already had a CS130 installed in the vehicle, the CS144 should not require any additional wiring...
What have others that made the change experienced? Did you add a resistor?
From various web pages:
"L-Terminal: This terminal is connected to the “Low” side of the warning lamp, with the lamp’s “High” side being fed by the ignition circuit. Some regulators require a 35-ohm resistance inline with this circuit if no lamp is used otherwise alternator damage may ensue. Some applications have a resistor connected in parallel to the lamp in case the lamp bulb opens up and burns out. The resistor will be there to provide a path for current and voltage. Some vehicles supply a 5Vdc reference to this terminal from their ECU or Computer; other vehicles don’t, so be aware of the various models of regulators. Other regulators may be tested by application of a 50-Ohm pull-up resistor to connect the L-Terminal to the 12Vdc source, I believe that any resistance between 35 Ohms (5-Watt resistor) and 500 Ohms (1/2 Watt resistor) can be used safely."
"The resistors provide a "tickle" for the charging sensor. The alternator was designed for a car that has a "dummy" light, which provides resistance for that sensor. So, if your car has no dummy light, there is no resistance, so there has to be a resistor somewhere in the system to provide a load."
The switched 'light' (terminal 1 on SI or 'L' on CS), must have 12V switched power with between 35 and 350 ohm resistance (typically the light itself). If below 35 ohm, the CS units will fail.
So if the above is true - I don't know what the resistance requirements are for the CS-144 designed for an Olds Aurora - Maybe I should add a resistor to the circuit just to be sure that I'm over 50 ohms...
Last edited by Spinman; 08-11-2008 at 12:02 PM.
Reason: additional info
Everything I've read to date has suggested that any late model CS144 alternator should work - just match the same frame style, clock position and mounting flange positions. So I didn't give any thought to searching for CS144 from a specific vehicle.
I installed the CS144 (140 amps / for a '96 Olds Aurora) and my battery warning light never went out. Quickly turned it off, not wanting to damage anything.
Reinstalled the CS130 - and naturally, the light went out when the engine was running.
Out of curosity, I took the CS144 to the local parts store and had it tested - everything is A-OK.
While they were preparing to run the test, I noted that they employed different wiring harnesses to connect alternators to the test equiptment. The cable for a '96 Olds Aurora Alternator is different than the cable for a '90 Corvette. I have no idea what's different between the cables (resistance perhaps?).
I suppose I need an alternator expert or a Delco-Remy engineer, but I wonder if there is something different internally between the 2 units I have. Perhaps the Corvette CS130 has a different resistance internally than the Aurora CS144 - thus the "L" circuit is not turning off the charging idiot light and telling the alternator that it is ok to proceed...
As I mentioned earlier - various web pages indicate that the "L" circuit requires resistance in the range of 35 - 350 ohms - yet I'm only measuring 14 ohms.
I hate to install a resistor in the line until I know what's really happening (and don't know if I install it in series or parallel with the existing idiot light).
The CS144 alternator I installed is a 140 amp from a "96" ZR1 Corvette. The internals are obviously different between the Oldsmobile and Corvette alternators.
Just wondering why you didn't buy a CS144 alternator for a C4 Vette?
Trying to save a few bucks using spare parts on hand...
Here's what I just learned from an alternator vendor:
The '96 Corvette LT1 CS144 is compatible with the wiring in the '90 Vette. The problem with the Aurora alternator is that the regulator used in the alternator is not compatible. The 712 regulator used in the 321-1131 alternator has a 14.6 volt set point(through Thermistor). There is a thermistor used in circuit due to the location of the battery. If you replaced the 712 regulator in your Aurora alternator with a 411 regulator then it would be compatible with you '90 Vette.