I've seem to be having an unusual problem with my electrical system. My car has a sunroof, which worked fine until a few years ago -- when it suddenly stopped working. The sunroof would move slightly and then stop after leaving a 1/4" gap. It appeared that the starter motor cuts out after a few seconds. I can then close it fine, but it will not open past that 1/4" inch. At first I thought something was stuck, but then it suddenly started working again. The first time it restarted working again was when the weather suddenly became warmer (how convenient!), but I could not find any blockage or interference with the cable or motor. The sunroof would continue to work fine for perhaps 1 to 2 weeks, before it would mysteriously revert back to not opening very far. Then, after 3-4 months, it would suddenly start working again. This cycle (works fine for short time, then fails for a long time, then works fine for a short time, then fails for a long time) has repeated itself over the past year or so. My mechanic thought that it was the sunroof cable or the sunroof motor but I don't think so, because of the cycling and because of the other electrical problem:

At about this same time that the sunroof started working, I noticed the following symptoms with my back up light: it would come on when I put the car in reverse, and then after I had moved a bit, it would cut out suddenly. This persisted for the entire time the sunroof was working; and when the sunroof stopped working, the back up light started working fine.

Note that the behavior of both systems (sunroof and back up light) is the same: each would start and then cut-out briefly thereafter. The fact that one work system works when the other fails makes me think that there is an electrical problem. I'm wondering if there is insufficient voltage, and that when voltage is sent to one system, not enough voltage reaches the other. Perhaps there is a voltage leak somewhere.

My battery last checked out fine, and I have a new alternator. Interestingly, this is my second "new" alternator in a year. The first replacement alternator lasted only 6 months.

The check engine light has not come on, and, in fact, it has never come on, ever. It does light up at start up, like it is supposed to do. So perhaps there is an electrical problem with the CEL as well.

So, does anyone know how the Corolla (1988, 1.6L 4AFE engine) regulates voltage? Is there a voltage regulator in the engine that may need replacing? If so, where might it be? Or is voltage regulation done by the engine computer?

For what is worth, when I explained to my mechanic this scenario, he seem skeptical, adding, "This is why people buy new cars -- so they don't have to deal with problems like this."

thats a line of bull, new cars DO have problems just like this!

As far as I remember my old box -1986 Corolla had alternator with build-in voltage regulator.

Does the brake warning light come on on the dash, or engine starts revving?

I think that most cars in 1988 had voltage regulators integral to the alternator.

Check the voltage at the battery with the car NOT RUNNING...it should be over 12 volts DC. A typical measurement from a battery in excellent condition with a properly functioning charging system will be between 12.60 to 12.75 volts DC.

Check the voltage at the battery with the car RUNNING at approximately 2000 RPM. ....it should typically read between 13.5 and 14.5 volts. This will tell you that the alternator/regulator are working fine.

Jay in MA

I've seem to be having an unusual problem with my electrical system. My car has a sunroof, which worked fine until a few years ago -- when it suddenly stopped working. The sunroof would move slightly and then stop after leaving a 1/4" gap. It appeared that the starter motor cuts out after a few seconds. I can then close it fine, but it will not open past that 1/4" inch. At first I thought something was stuck, but then it suddenly started working again. The first time it restarted working again was when the weather suddenly became warmer (how convenient!), but I could not find any blockage or interference with the cable or motor. The sunroof would continue to work fine for perhaps 1 to 2 weeks, before it would mysteriously revert back to not opening very far. Then, after 3-4 months, it would suddenly start working again. This cycle (works fine for short time, then fails for a long time, then works fine for a short time, then fails for a long time) has repeated itself over the past year or so. My mechanic thought that it was the sunroof cable or the sunroof motor but I don't think so, because of the cycling and because of the other electrical problem: 

 

At about this same time that the sunroof started working, I noticed the following symptoms with my back up light: it would come on when I put the car in reverse, and then after I had moved a bit, it would cut out suddenly. This persisted for the entire time the sunroof was working; and when the sunroof stopped working, the back up light started working fine.

 

Note that the behavior of both systems (sunroof and back up light) is the same: each would start and then cut-out briefly thereafter. The fact that one work system works when the other fails makes me think that there is an electrical problem. I'm wondering if there is insufficient voltage, and that when voltage is sent to one system, not enough voltage reaches the other. Perhaps there is a voltage leak somewhere.

My battery last checked out fine, and I have a new alternator. Interestingly, this is my second "new" alternator in a year. The first replacement alternator lasted only 6 months.

 

The check engine light has not come on, and, in fact, it has never come on, ever. It does light up at start up, like it is supposed to do. So perhaps there is an electrical problem with the CEL as well.

 

So, does anyone know how the Corolla (1988, 1.6L 4AFE engine) regulates voltage? Is there a voltage regulator in the engine that may need replacing? If so, where might it be? Or is voltage regulation done by the engine computer?

 

For what is worth, when I explained to my mechanic this scenario, he seem skeptical, adding, "This is why people buy new cars -- so they don't have to deal with problems like this."

A defective battery could cause the alternators to fail early. Has the same battery been in the car through this alternator problem?

Another thing to remember. The battery must be fully charged prior to installing a new alternator.

Alternators are designed to maintain a charge, not charge a battery from dead. Many people make this mistake and fry brand new alternators.

A loose clutch won't stop the engine from spinning when you turn the key but a defective clutch switch will. You can replace the switch fairly easily or jumper the switch and see if that problem goes away.

Good luck,

Jay in MA

As far as I remember my old box -1986 Corolla had alternator with build-in voltage regulator.

Does the brake warning light come on on the dash, or engine starts revving?

The engine seems to work fine; I did have some problems starting the car a few days ago, and it appears to be a loose clutch, perhaps the switch, but this is a new problem. If the alternator has a built-in regulator, then perhaps it needs replacing again? What could cause a car to go through/eat alternators? The belts seem fine, the car has sufficient power, gas mileage seems okay, and the front lights and tail lights seem to work fine.

Good point. The battery may need replacing.

It may have burned out the newer alternator.