Electrical Problem with Previa

[Makelo]

Guys, I'm having a weird electrical problem. It always occurs at night with the headlights on. After a while running the van, when I step on the brakes, for a fraction of a second the following occurs: Battery light flashes, dash lights deem out, radio loses ground and turns off. If I continue to hit the brakes (say during a slow moving traffic on the street) dash lights, battery light will blink, radio turns off and on, then my healdlights turn off!. This issue has been present before and after the following repairs: SADS coupling and rebuilt alternator with new alternator belt. I'm starting to think my electrical issue is more related to a fuse box. Let me know if any of you guys have had similar electrical experiences with your Previas

[timsrv]

Sounds like a weak alternator to me. If you have an open diode on the diode block, the alternator will still charge, but will not be able to do that AND keep up with lights and other accessories. Check the big wire coming off of it to make sure it's tight. Also make sure the accessory drive assembly is grounded to the frame. Start the van, have somebody hold RPMs at around 2k, turn on lights, fan, etc and check voltage at the battery. You should see above 13.5 volts. If less, pull the alternator and have it load tested.

Before pulling the alternator, you should also check the condition of the fusible link box (positive cable at the battery). Here's a post that shows how to check: http://www.toyotavantech.com/forum/showthread.php?395-Intermittent-Starting-Problems-amp-Check-Engine-Light!!!-91-Previa-LE-AWD. Pay particular attention to the underside/base of the fuse that's labeled "ALT". Tim

[Makelo]

Thanks Tim, I will do the testing on the alternator. But I'm having the feeling the Battery Fuse Box could be the culprit of my electrical issues. I though about the alternator, that's why I replaced it, but this new/rebuilt unit is doing the same thing. Do you know the cost for the fuse box? I called my local dealer and I was given $90.00 for the fuse box and $400.00 for the positive cable. Don't know if I was quoted correctly because I don't know why the cable would be more expensive than the fuse box

[timsrv]

I have heard these were expensive (similar to the prices you mention). I have seen this problem on one of my Previas (pics in that other post), but due to the price I never considered purchasing these through Toyota. There are lots of Previas in Portland area salvage yards, so I would just pick up a good used ones. At least half of the ones I've seen in the yards were in good shape and it's likely they will sell for around $10. The positive battery cable would be easy for a wire shop to make. I'm guessing less than $100..........but you probably don't need it. I'm guessing you can wire brush or grind or the corrosion off the end and put some anti-corrosion grease on it (They sell this stuff specifically formulated for battery posts & terminals). If the terminal needs to be replaced that should only cost a few bucks. Good luck. Tim

PS: Not all of these fusible link boxes are the same. Make sure the one you get has at least as many features as the one you are replacing. Here's a post that shows the difference: http://www.toyotavantech.com/forum/showthread.php?157-Battery-Fuse-Box

[Makelo]

Thanks Tim, saw the link, I will make sure the one I get is for the SC version. I'm gonna head to my local yard and see if I can scoop up a fuse box, nice project for the weekend :) I will keep you guys posted

[TheMAN]

I've got bad reman alternators before, a whole bunch of them from parts stores... I won't buy them again... I either will take it to a local rebuilder who will do the right job or I will buy a denso aftermarket reman which will be truely like-factory condition

[timsrv]

Agreed. Denso is the only remanufacturer I'd trust rebuilding a Denso alternator. For what it's worth, my Previa alternator developed this problem at around 180k miles. I was in a jam so I called Napa. I figured I'd run one of their cheap ones and keep my original to repair later. They wanted almost $200 for the alternator + a ridiculous core charge ($80 if I remember right). I got annoyed with that so I drove to the pick-n-pull, pulled the alternators off of 2 Previas, disassembled there in the yard, and took diode assemblies, regulators, and one set of brushes (were almost brand new). The guy at the counter charged me $15 for the lot. I pulled my alternator in their parking lot and swapped the diode assy (2 of my diodes were burnt where the stems come out) & the brushes. That was about 3 years ago and it's been working great ever since :dance2:. Never give up that original alternator for an aftermarket rebuilt one. The factory Densos will go forever but once in a while a component will fail. These are easy to fix. The aftermarket rebuilds use poor quality components and do not last very long. Sometimes they are bad right out of the box. Tim

Here's a couple pics of my damaged diode assy:

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/previa%20electrical/IMG_1515_zps3ca223c7.jpg

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/previa%20electrical/IMG_1513_zpsb900ff90.jpg