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Discussion Starter #1
I'm new with Alfa's. but been "playing" with car for 25 years and have never had this happen. Got my car to run after adding a new fuel pump and fuel relay. The Alternator light was on after it started so I installed a new alternator and battery. Just when I thought I was good to go ,I rev'ed the engine a little ( maybe to 2000 rmps My tach doesn't work) and the red light came on! If:confused::confused: I shut the car done and restart it the light is off. Then as soon as I rev the motor the light comes back? What could cause this?

Thanks for any help.
 

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Discussion Starter #3
My car is a 1986, Is the reg part of the alternator?

The car at the auto parts place told me the reg is built into the Alternator. All connections seem tight
 

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Need more info for sure on this. Also year of your car.

If yours has an internal voltage regulator...it is super common to see the red light on after start up or at least remain on until after the first revving. This is the VR kicking in and should shut the light off.

Now with yours kicking in after revving....and a new alternator already installed....makes me wonder if you have the right VR in the alternator you purchased. Also make sure the single green wire is connected and not corroded at the terminals.

Also check your fuses....

Best Regards,
John M
 

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Discussion Starter #5
I was able to confirm 14.4 volts But the light still comes

I just started my car after I hooked up a voltage gauge. I get 14.4 volts after I rev the motor and the Alt light still comes on?
 

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Could still be the brushes or regulator.

Does the voltage stay the same when you rev it and get the light to come on?

If it drops, then you're still prolly looking at brushes, connection, or possibly a loose belt.

The regulator isn't built in persay, at least not in the common sense where you have to actually crack things open to access it. It's mounted on the back of the alternator housing with two screws.
 

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Discussion Starter #7
The volts stay the same, Looks like 12.8 Then..

I rev the Motor and the Volts go to about 14.4. In fact it seems that the light comes on when the volts go up. At idle the volts are the same as when the gauge is hooked up without the car running. ( About 12.8) Do you know what those two relays do that are mounted on the passenge side of the engine bay near the windshield washer bottle? Thanks
 

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The relays are for your electric auxillary fan that sits in front of the radiator.

One turns the fan on when you turn on the AC, the other turns the fan on when the temp sensor located on the radiator fan shroud says things are getting too hot.

The AC one will turn the fan off with the key.
The temp sensor one will allow the fan to run after you shut down and walk away. (it'll stop automatically once the sensor signals it's cool enough)
 

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Sd455,

It can be a bit tedious to find the source of why the warning light comes, but make no mistake: something is not 100% right. Here is a thread that you may find useful: "Electrical Question.. Help"

Best regards,
 

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I rev the Motor and the Volts go to about 14.4. In fact it seems that the light comes on when the volts go up. At idle the volts are the same as when the gauge is hooked up without the car running. ( About 12.8)
That sounds odd.

Granted voltage may go up a little bit once the alternator reaches it's peak output RPM, but to go from 12.8 at idle to 14.4 while revving seems a bit much.

Voltage on a gauge at 3000rpm should be 13.7-14.7, and the lower value should be attainable with at least the high beam headlights turned on.
 

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When the alt light comes on, it means that there is a voltage potential across the bulb. Since the alt is outputting 14+ volts, it would appear that the alt is okay (although, as preveously mentioned, the green wire in the junction block may need cleaning). If so, then the the problem may lie in the switched power supply to the bulb. I'd start by cleaning fuse #8 followed by the connections at the junction block (left inner fender).
 

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Discussion Starter #12
Thanks for you help

I get this car back on the road even if i have to rebuild it one part at a time
 

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Does this mean anything ?

When I disconnect the neg to the battery after the car is running ( Just at idle without the alt light on ) the car stalls. Does that mean the battery needs to be hooked up for the car to run or does it mean just because I'm seeing 14 plus volts on my gauge doesn't mean the volts are finding there way back to the battery? Could the be?
 

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Please note that the ECU's, you have 2 (FI and Ignition) do not like for the battery to be connected/disconnected when the ignition switch is on!

This is plainly stated in the factory manual and the engine maintenance manual for the S3.

Best regards, Elio
 

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Discussion Starter #15
Thanks, So that simple test confirms the Alt is bad?

If so I can't understand why I'm reading 14 plus volts after I rev the car a little. I thought a bad alternator would either put on no volts or very little volts.
 

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Discussion Starter #16
Thanks Elio, I'm glad I had the switch turned to off

I heard that having an Alfa's and keeping it on the road is a labor of love.
 

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If so I can't understand why I'm reading 14 plus volts after I rev the car a little. I thought a bad alternator would either put on no volts or very little volts.
No... actually Elio is 100% right. If you have a series 3 or later Spider, which are the ones with the ECUs, they will turn-off if you disconnect the neg battery terminal. (At least at idle they will.) In the Spiders without ECUs, then it is different, and you can run the car.. What year is your Spider?

Best regards,
 

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Discussion Starter #18
My car is a 1986

Gee I thought the alt would power the car after it's started. So if the car stalled the alt is bad.
 

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If so I can't understand why I'm reading 14 plus volts after I rev the car a little. I thought a bad alternator would either put on no volts or very little volts.
The alternator can go bad in numerous ways. But you stated you just replaced it with a new one. Do you have a reason to suspect its bad?

It should put out 13.5-14.5 Volts depending on the voltage regulator.

I doubt you have it hooked up right.
IF you have the right alternator its a simple hook up. Single red wire from the driver's side inner fender to the main post on the alternator. And there is a single green wire running from the harness to the D+ post on the alternator. This wire controls turning that light off. As well as that fuse #8 papajam mentioned. OHM meter the wire and the fuse and the connections.

BBest Regards,
John M
 

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Discussion Starter #20
John, I'm sure I hooked it up correct

I went to the store, Got the new alternator from the box, Removed the little black relay from the old one ( The guy at the store said it's for the radio) Plugged the lead from that little relay into the same spot on the new one and then at my home rehooked the Large red wire and the small green wire. Before I put the new alternator in the red light went on the first time I started the car ( Which I was told was the 1st time in maybe 4 years it was started) That's why I purchased the new alt. I'll find my way with this car.
 
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