Replaced thermostat and now brake and battery light on??

[dieseldaddy]

Jut put a new thermostat in my 91 Corolla wagon and now the brake light and battery light in the dash are on and will not go out. Wondering if this is because I didn't unhook the neg batt terminal b4 doing the work? battery is fine, e-brake is not on and car rolls freely in neutral. (5-spd manual)

Is this something easily fixed or do I need to have a diagnostic hook up to clear them? I have already unhooked the battery for about 30 mins hoping to reset it somehow...no luck.

Side note: This was the EASIEST thermostat replacement I have ever done!

[REN69]

Man, we were just talking about this topic about a week or so ago... most likely your alternator is not charging properly anymore and it's dying on you.

[dieseldaddy]

What I don't get is why all off a sudden instantly after I change the t-stat?
A nasty coincidence? Karma? Pissed off mother-in-law?

I'll check the alternator tonight after work.

[dieseldaddy]

OK so I tested the battery w/car off = 13.3
Tested with car running = 14.4
Turned on headlights and dropped to 14.2
Turned headlights OFF and immediately went back to 14.4(flickers btwn 14.4 and 14.5)
Is there anything else I should check? There is what sounds like a noisy belt the last few days but I thought that was cuz of the weird changes in temp around here: 20 degrees in AM/65 by noon / 20 again by 10pm. Read that the noise could actually be the bushing in the alternator? Thinking of just replacing the alternator and belt. Local guy will do it for total $175. (one hour labor and $100 alt and belt) Of course I can do it too...but not certain its going to save me all that much in the end. I like to work on them...but I'm a weekend warrior and its only Monday...

[SCT]

Alternators have built-in diodes, rectifiers, whatever to control the outputs it gives to run the car and charge the battery. The voltage may still read above 12V, but the amperage could be jumping from not enough to enough or beyond. Happend to my Taurus; the light sometimes flickers for no reason, sometime there's power then other times none. One of three built-in diodes died and caused slight problems, the amp would flctuate sometimes exceeds or die out then go back to normal. Ultimately, battery light ON.

Just change the alternator. As for the belt, if it's not cracked, just add a bit more tension to it and it'll do. If cracked, change it.

[4doorGTS]

It sounds like its charging and those voltage readings you got are good but to truly test an alternator you need to test amperage. On a side note my dads 89 gts had this same issue but everything worked properly so I figured a broken wire in the harness somewhere. You might have moved around some wiring just enough to cause something like this but I cannot tell you exactly which circuit would cause those lights to go on.

[Xen2050]

The Toyota alternators have lots of replaceable parts, hit up a junkyard/pick your part and pull the easily unscrewed parts off of the end of the alternator (the diodes, regular, and brushes, easy to see longer brushes and can test the diodes with a multimeter) then just replace your old alternator parts with the "new" ones. Should save close to $80 or so compared with a replacement $100 alternator (or save $100 if the parts fit in your pocket ;-)

One corolla had bad diodes in an alternator for over a year, it seemed ok and the bat & brake lights didn't come on, but it might've ruined the new battery that should've lasted 5 or 6 years instead of one (or just cheap canadian tire batt).

[dieseldaddy]

Going to replace alternator this weekend.
So now I have a few choices... Rebuilt by local shop=$80
Junk yard=$35 (none I found will sell me just parts)
New from AutoZone=$80-$85 (+core)

....sounds like a no-brainer. same price for new as rebuild? There are 2 different ones at AutoZone: 70A and 74A. Which is the preferred? Why would I want/need one over the other?

Sorry for the seemingly simple questions guys... I really appreciate your help!

[Xen2050]

If it's a new Nippon-Denso (ND) alt. then go for it, watch out for the off brand jobber alts, everything I've heard about them says they last 1 or 2 years, so you'll need a free lifetime warranty, and enjoy replacing them.

The sounds yours was making might mean it's got bigger problems than a few parts though. I'd try a junkyard with free exchanges & test it free at a parts store like canadian tire or partsource. Or, the 74A might be more power, so might be better?

[dieseldaddy]

Awesome (as usual) guys.
Thanks a ton.

[freakinbox]

I got one near my ex's house for $199 lifetime warrenty. Which was alot cheaper than the regular ones else where!

Best way to test a battery or alternator is take it to a place that has the equipment to test them. Gives them a more through read out then what you are doing.