Ok, so here's what it's doing, the car idles on the notch right above 0 rpms(guessing this is 500 rpms but it may be less and it sounds like the rpms fluctuate up and down by 100 to 200 rpms.
If the car is idleing, it doesn't show that it is charging at the battery terminals or on the connections on the back of the alternator(sits around 12.4-12.6 volts). If I blip the throttle just a little bit to around 1000 rpms and hold it there the voltage jumps to 13.8 volts. When I let off the throttle it stops charging, the battery voltage does increase by .1 to .4 volts roughly. So I'm pretty sure that it is actually charging.

I checked the voltage coming from the exciter wire with the key on in start position 2 and it only reads 11.5 volts even if the battery is reading 12.6 volts. With the car running and revved up the exciter wire gets 13.8 volts.
I've tried two different alts on the car and they both do the same thing, they are both used alternators though.

Now with all of this said, is this an alternator problem or is my car idleing too low?

Edit: guess I should say what kind of car it is, it's a 1993 940 n/a with the Denson 14v-100 amp alternator.

-Dillon

 

It should charge at all times, even if it's just at idle.
Are your cables healthy the whole way through? If they're cracked or messed up inside the insulation it won't transfer the charge correctly. Pull the alternator and go get it checked at a parts store and see if everything is healthy. If you can get the whole car up there you might be better off, though.

 

Yeah, I mean I knew it was supposed to charge at idle, but if my idle is just way too low and is turning the alt pulley way to slow then that would cause that alternator not to kick in and start charging wouldn't it? And yeah the car actually keeps a good charge as long as I'm driving it, I drove it 150 miles the other day without any type of hiccups or anything haha

 

Sounds like the charge rate of an "unexcited" alternator. When you "blip the throttle" it gets excited, starts charging. Is your ALT light on your instrument panel working? Does it come on when the key is in position II, then go off as you start the car?

 

Thats what I was thinking too lev, but is the ALT light the same as the battery light? If so then yeah it comes on in start position II and goes out after I start the car.

Also just noticed this earlier, when I let it stay at idle eventually the SRS light and ABS light come on very dim until I rev the car up a little bit.

 

OK, that helps. Yea, BAT and ALT, same thing, all read the charge rate.

You probably have worn brushes in the alternator. You can replace those or just get a rebuilt alternator. The cost varies. The brushes can be had separately for around $40 but then they have to be soldered in place. A rebuilt alternator can be had for almost as little as that. Many times a rebuilt alternator is just new brushes, AKA "regulator".

 

Well see one of my friends had mentioned that so we took a look at both of the alternators that I tried on the car and one of them, the brushes looked a little worn but not to awful bad and on the other alt(the one that's on the car now, the brushes looked even better probably has about 25% more material on them then the other ones. And maybe worn brushes is all it is but I'm stubborn haha.

The only reason I'm so hesitant to go out and get it rebuilt is just because I have a gut feeling that it won't help. I really feel like my car just isn't idling high enough and isn't letting the alt get "excited", could this happen? Or would the alt always charge no matter how low the rpms are?

 

500 RPM is too low of an idle speed, it should be closer to 700rpm, and it should be rock steady once the car is warmed up. in fact, when its very cold, it should be HIGHER than 700, like 800 or 900, til it warms up sufficiently.

if its NOT doing this, it sounds like your idle control valve, and/or idle throttle switch are malfunctioning.

 

Ok that's what I was thinking Pierce, it isn't becoming rock steady no matter how long it stays running. And here in Alabama it never gets very cold, take today for instance it's 86 degrees F outside, so cold isn't an issue haha. I think someone also messed with everything that looked like it adjusted the idle. Every screw is adjusted as far as it will go, so I think I'll go outside and attempt to fix someone else's mistakes again haha.

Ohh and the IAC works, well I hooked it up to 12 volts and I heard it click on and off and it never got stuck, I may clean the connector today too

 

I forget the exact procedure, but the general idea is, with the engine fully warmed up, you disconnect the idle air controller's electrical connection, and adjust the throttle body so the engine is idling at 500rpm. also make sure the idle switch is engaging at idle, and switching off just above idle. When you plug the IAC back in, the idle should be regulated at about 700rpm.

 

500 vs700 rpm should not affect your idle charging rate. By all means, try to fix the idle to smmoothen out and go up a bit but that won't be decisive. Your alternator is faulty.

 

Ok, well I just tried to do it like that and when I set it at 500 rpms with the IAC unplugged it was fine, no fluctuating rpms or anything. When I plugged the IAC up it shot to 3000 rpms and wouldn't go back down. When I unplugged it it went back down to 500 rpms. Does this mean that the IAC is bad or is the idle switch bad? Or what else would cause it to do that?

For now, I've got the IAC unplugged, and just have it adjusted to 1000rpms, it seems to run better than it was running, I may get worse gas mileage but it sounds better, doesn't sound like its going to die at any minute.

 

that sounds like either hte IAC is bad, or the signal that controls it is always-on.

this is a 1993 940? so its LH 2.4? there's a "DTM#3" procedure with the diagnostic box under the hood that cycles all the actuators, including the IAC. it might be worth running this and verifying that the IAC opens/closes on demand.

see http://www.volvoclub.org.uk/faq/Engi...agnosticCodesi for how to activate DTM#3... I would remove one of the hoses from the IAC, and stick a clean piece of clear vinyl hose on to the IAC, and gentrly blow into this hose while the test is running, you shoudl feel the airflow start/stop as it opens/closes.

if that works, then the IAC should be working fine.

 

Ok, I'll check that tomorrow, will it hurt the car if I drive with the IAC unplugged?

 

dunno why it would hurt anything

 

Check out the post by swiftjustice44 on this thread:

https://volvoforums.com/forum/volvo-...-issues-50270/

It has a good writeup on the procedure for setting the idle on an LH2.4 fuel injection system.

 

Thanks act1292, that looks like it'll help alot, I'll follow those steps tomorrow when I work on the car and try to tie up some loose ends.

Sorry lev, I just noticed your post, and yeah, thats my conclusion is that I've just tried 2 bum alts on the car . I'm going to head to an alt rebuild shop this weekend and see how much they'll charge me to rebuild one, hopefully it's not an arm and a leg haha.

And I still haven't done the diagnostics yet, too lazy and the temperature outside isn't helping me any haha.

 

Ok, finally got an alternator that works, changed from a Denso 100amp to a Bosch 100amp and it only cost me $26 from my local pull-a-part. It's charging at 14.26 volts now at idle and works like a dream, it is also doesn't get as hot as the denso did. The Bosch is also considerably bigger, never noticed this until yesterday. I also picked up an IAC, extra fpr and few misc trim pieces and relays while I was there. I've got to modify the plug for the IAC though bc it came off a 1995 940 turbo and theres a little variation in the plug. I'll get to that tomorrow.
I picked up an intermittent wiper relay because I thought that was my problem with my wipers but the problem is still there. With the relay in and the switch on start position II the wipers stay on with the wiper switch in the off position. With the relay out and switch on II the wipers work on slow and fast speed but don't return to rest when I turn the switch off. What could this be?