[lerxst_x]

Yesterday on the way home from work, when I started the car, my ABS, TCS, Brake and Air Bag lights came on. As I drove home, when I came to a stop, first the Air Bag light would go out, and then the ABS, TCS, and Brake Lights would go out (these three at the same time). On pulling a way from a stop, as the RPM rise, the three brake related lights would come on simultaneously, and then a few seconds later the Air Bag light would come on. I also noticed that as the RPMs rose above idle, my A/C fan (the inside one, that blows at me) would gain speed. Coming back to a stop would repeat the process (lights go back out, etc). I don't seem to have a lack of electrical power at any point (lights stay just as bright, etc). I'm thinking that the voltage regulator has failed or is failing, allowing voltages to get too high when RPM is above idle, causing the ABS system and Air Bags to error out. I've got probably 130k mi on the car, the battery was replaced last October or November. Since the problems seem to be RPM and electrical related, I'm thinking I need a new alternator.

Can any of the experts looking at this forum concurr?

Thanks,
Tom

 

[ricerrx7]

Reading the codes might be a good idea...

 

[BobMs_wht2k2]

and checking the battery would as well. Get an electrical system check.

 

[cclngthr]

Reading the codes might be a good idea...

If there are codes.

A test on the charging system will tell you if the voltages are too high/low. Get that done along with what Bob said.

 

[blmqzjc]

If it is the alternator, it will take the battery along with it - quickly. I think every time I've replaced an alternator, I also had to get a new battery as it was ruined too.

Will the car start after having been off for a few hours, or do you have to jump it?

 

[ricerrx7]

I did. I said to get the codes read. That's what you do when warning lights come on. Now, if the alternator is OVERCHARGING like he thinks it is, then how the hell is pulling the cable off the battery going to prove anything? PLUS, if it is overcharging, and there is no buffer in the system anymore (I.E. the battery), then the ECU and TCS computers are going to take the uneven overvoltage and possibly cause problems up to and including frying the computers.

 

[lerxst_x]

Okay, well, didn't mean to start a flame war.....I stopped by an O'Reilly on the way home and had them do their electrical system check. The battery alone (car off) came in at 13.2V, with the car running, ~2000rpm, the voltage came in at 13.6V, which IIRC seems a little low. The car does not have to be jumped when it sits (so far). The I'm thinking that I originally misread how fast the A/C fan was blowing; I'm thinking that it only gets up to speed as the rpms climb.

Shouldn't the voltage be somewhere a little above 14V? If so, with the mileage I have, wouldn't it be reasonable to assume that the alternator is dying?

 

[cclngthr]

Pete, with a non-ecu driven engine, unhooking the battery to check the alternator was OK. However the computer, which is very sensitive to voltages, WILL INSTANTLY fry if it sees too high of voltages.

The alternators regulator is dependent on the battery to regulate the amount of spike the system can handle. Without the battery hooked up; a draw, the regulator will not set a maximum voltage.

The point is that you can't use a old school technique on a modern car as what Pete likes to use.

 

[lerxst_x]

Oh, yeah, the diodes were okay....

 

[cclngthr]

thank you cclngthr for explaining that to me, i appreciate it.

You have to remember that when you momentarily disconnect the battery, the alternator (if working properly) will go at max voltage very quickly. I remember when I was dead in the water at night and a mechanic buddy of mine came over and tried jumping my 74 Chev El-Camino, which was dead and still would not start due to the battery being dead, he had to unhook my battery so I could get the car started. Once it was running, he disconnected his cables and my interior light went extremely bright (twice as bright as it normally was) until he reconnected my battery so I could get moving. He said afterward that the voltage is partly regulated by the battery and it provides the buffer so the charging system will work properly without things going too dim or bright.

On new cars, the ECU regulates the alternators output. Here, you cannot unhook the battery for any reason while the engine is running. The battery provides the power to excite the charging system, plus acts as a buffer so the ECU will regulate the charging system properly. On the XD, the alternator's regulator is separate from the ECU. On the MD, it likely will be regulated by the ECU. The HD's regulator is like the XD, but the ECU monitors the voltage as a secondary system.

On my Mazda 3, the ECU regulates the alternators output (having 2 regulators). Instead of ramping up the voltage quickly, as after a cold startup, the system slowly increases the voltage. Once run for 5 minutes and the engine is shut off then restarted, the regulator increases the voltage quickly because the ECU has enough power in that area of the computer to regulate the voltage quickly.

 

[lerxst_x]

I posted an update on my situation, but I think it kind of got lost in the noise....anyway, I went to an O'Reilly and had them run an electrical system check. The battery checked out okay @ 13.2V. The alternator charged at 13.6V, which IIRC seems a little low. They did say that the diodes were okay in the alternator. I think that I misread how the A/C fan was reacting to engine speed. It seems to me now that the A/C blower fan really on reaches it's normal speed when the RPMs are 2k or above. I also noticed that when waiting to turn (at idle) the dash lights would kind of pulse with the turn signals. I haven't had a chance to get the codes scanned, but with this information does it seem that the alternator is getting weak?

I really didn't mean to start a flame war, just looking for some advice.

Thanks very much!!!

 

[BobMs_wht2k2]

Check your negative cable that goes under the battery tray. If the cable is as old and weak as mine was it may be corroded, giving you a poor ground. Poor ground would give the same symptoms as a bad alt or battery. Also check the positive. You're at 8 years on the car, if they both haven't ben replaced yet it may be time.

 

[LeShadow]

Check your negative cable that goes under the battery tray. If the cable is as old and weak as mine was it may be corroded, giving you a poor ground. Poor ground would give the same symptoms as a bad alt or battery. Also check the positive. You're at 8 years on the car, if they both haven't ben replaced yet it may be time.

Had to change mine on my '99 here... Replaced the Pos cable...

Cables are easy to test. Take some booster cables, and put connect the Pos directly to the amp, and then, do the same with the Neg to the body. If looks fine, then try to identify wich one is the problem.


If u change the pos... don't bypass the fuse.

Good luck mister !


BTW... Welcome in EXD !

 

[cclngthr]

Check your negative cable that goes under the battery tray. If the cable is as old and weak as mine was it may be corroded, giving you a poor ground. Poor ground would give the same symptoms as a bad alt or battery. Also check the positive. You're at 8 years on the car, if they both haven't ben replaced yet it may be time.

Also check the ground from the engine to the chassis.

BTW, those 6 gauge battery cables are not the best, and the 10mm bolt that secures the cable to the chassis is not the best either. There is a 14mm bolt near the drivers side strut tower under the wiring harness. It is this bolt that is used as a ground point for the engine to chassis ground. Using this point is better than the one under the battery tray.

 

[lerxst_x]

Finally was able to take a look at the cables, they didn't look too bad, I did see some corrosion where the cable attaches to the fitting that goes on the battery post, but I think that it is still making a connection. Did not see any corrosion where the negative cable hooks attaches under the battery tray. I did notice that the battery seemed to have vented some moisture out of the vents on either side of the top. Battery seemed very warm, but maybe that's just because everything else was warm in the engine compartment. The positive terminal seemed to be hotter than the negative, FWIW.

I did not remove the battery completely, as the positive terminal was stuck on the post (just as it was when I had to replace the previous battery last fall) and I didn't want to force the thing off, for fear of breaking the battery.

Oh yeah both my headlights burned out when I turned them on this morning. (I checked, and the filament had burned through).

Further suggestions???

Thanks again.

 

[BobMs_wht2k2]

REplace the cables. Trust me. I used to deal with lights that would dim everytime the A/C cylced, or verytime I used the windows..... all went away with a bigger battery and new 4ga cables. I can't remember the correct lengths needed, but they are less than $20 for both negative and positive for hte car.

 

[cclngthr]

REplace the cables. Trust me. I used to deal with lights that would dim everytime the A/C cylced, or verytime I used the windows..... all went away with a bigger battery and new 4ga cables. I can't remember the correct lengths needed, but they are less than $20 for both negative and positive for hte car.

If I remember correctly, I used a 6 inch negative battery cable (which I did relocate the position where it attaches to the chassis). Not sure about the positive cable where that ends up at, but the starter to battery cable should be approximately 24-36 inches (I did not replace that on the XD I had).

 

[lerxst_x]

I've played around with various new ground points, and have not noticed a change in the behavior of the warning lights going on and off. I've made a couple of longer highway trips (8-10mi @ 65-70, most of my driving is around town on surface streets) and after the longer trips, I'm smelling a hydrogen sulfide rotten egg smell. I'm beginning to suspect more and more that my voltage regulator is not regulating, and that I should replace the alternator. What do y'all think.

Thanks!
lerxst