Topic: strange check engine light today.

[midnightcwby]

Most definitely the alt or voltage regulator at that point
 
10 volts is terribly low.  As I mentioned before; under high drain, with the alt full fielded working its balls off, you shouldn't see ANYTHING less then about 12.5volts.  If it's below 11, you can rest assured your alt isn't doing a whole lot to put back the voltage your jeep is taking from your battery.  I'm surprised you haven't noticed slower cranking speeds when you start 'er up in the morning  :shock:

There is a tiny chance your volt gauge is off due to a poor connection. This would cause a little higher than normal resistance in the volt gauge circuit and cause it to read a deceptively low voltage reading.  To dispel this possibility, I suggest getting your hands on a multi-meter (aka VOM, DMM, ect.).

Check the battery voltage when the Jeep is off and note what it's at. Then have an assistant start it (if your lazy like me  ) and check to see that the voltage at the battery increases.  With everything off and just the jeep running, you should be somewhere in the neighborhood of 13-13.8volts.  My jeep runs at 14v.  A reading as low as 12.5v could be seen, this just means the battery is fully charged and the alternator isn't working very hard to maintain it.

The next check you can do to ensure your alternator full-fields properly is done while the engine is running.  Have your assistant turn on all the electrical crap they can... The headlamps on high beam, the wipers on high, and the heater blower on high should do it.  I don't like to turn on turn sigs. or flashers because it causes a rhythmic voltage dip which looks funny on the meter as your watching it.   With all of this stuff running, the voltage shouldn't dip below 12.5volts (Especially if it read 13 or so before you put the load on it).

If the voltage falls on it's face when you do the last check (full field test) or if the voltage doesn't increase much or at all when the jeep is started, you can pretty much bet you either have a problem with the alternator itself, or the built in voltage regulator and you'll need to put a new one in.  I think these are Jap Denso's or something similar, so they're probably $100+ (I would guess between $125 and $145).  That sucks.  Good luck and let us know what you find when you test it (or have it tested somewhere if you decide to do that instead)!

[littleredbeater]

well after a half of a can of brake cleaner with engine off, and the other half while running I managed to convince my alternator that it had some life left in it. haha Just thought I'd share that with you all. $3.49 for a can of brake cleaner is better than $100+ for an alternator.

[Dare2BSquare]

Here is an interesting one for you...

I had an '89 S10 Blazer 4x4 before I got my wrangler. Never had any problems out of it even though it had 196k on the odometer. But, when ever I went to the land that I bowhunt on, every time I came out, at the same place on the gravel road the check engine light came on. I could drive about 300 yards down the road and it went off. It never came on anywhere but this particular place on this gravel road. And it never came on as I was going in, only coming out. I suppose it must have been some type of electrical interference in that particular spot.

[Jeffy]

33 is related to A/C and can be ignored. 12, 33, 55 normally pop up when there are no problems. That leaves 41 and 22.

Does your temp gauge work?  What's it say?  The sender for the computer is on the head located behind #4 cylinder.  I think it's on the right side as you look at it.  There should be one wire going to it.  Even if the gauge works, the sender for the PCM migth not be working.  That leaves 41.  Alternator going bad?

[littleredbeater]

funny you mention the temp gauge. First, I thought the PCM uses the one in the thermostat housing? Second, my gauge is not working so I buzzed out the wire all the way back to the plug that connects to the gauge panel (purple wire) and it's ok, so I put a new temp switch in. (not sure why they call it a switch but whatever) even with the new sender in the gauge still doesn't work. I put a DMM on the sender and it is working so could I have a bad gauge? I think I must but can I just change the gauge or do I have to change the whole gauge panel? Anyone have a spare?

[chardrc]

aw specking of having bad gas... on vacation in colorado 2 years back we got a bad tank of gas in our 49 willys and when we got on the trail (not knowing of the bad gas) we started going up hill and as the trail got roffer the engine lost more and more power and ran ruffer.. so long story shortend we ended up frying the starter so we had to turn it around on the trail by hard and had to sitt al 4 of us in the jeep rollit down the hill bunching all over the place to pop the clutch to starrt the jeep......

luckly we have some relatives that lived cose by with a nice garage cumplete with a pit... so we rebiult the carb rebilt the starter and refined our trail mounted eklectric fuel pump instaled days later when going up mount blonka

but the next day we had to head home.. but we couldnt leave the trail un concered so we did it from the other side..but we didnt know yet that we had bad gas.. but we figured it out halfway up the hill.. buit after 2 on trail carb rebiulds we made it to the top of the trail...


well that was a bit long and off topic.. but there it is.