Ok so had a bad battery and alternator switched them out. Three more alternators and still getting no voltage increase when the car is turned on. I have tested at the battery and the alternator post. 12v and then dies slowly and even quicker when lights are on and such.

So I checked the dash and pulled out the bulb and put a bulb from another place in it and it will not light up when key is turned to 2.

So i then resodered all the joints on the board still no light. However when I test the excite wire I am getting 12v threw it which makes no sense seeing the light never lights when the key is turned to 2. I have tried everything I have found on here and its a dead end. Please need help have been trying to figure this out for 3 months. It's my only car and it's so frustrateing.

1994 volvo 940 with 189k

 

did you test the D+ ('excite') wire when it was unplugged from the alternator ?

 

Well, many ways to handle this but try this: the alternator SHOULD begin charging even without the exciter light once RPMs go over 2,500. I presume you have a multimeter? If not, get one. Measure first the available volts in the battery. Start the car, measure the volts now. Below 13.5volts? Rev up the motor to above 2,500rpms, see if the alternator starts charging. When I get one of these, I just rev it up to get the alternator to work... Make sure the connections are good and clean!

You are getting 12v, that's what the battery you have is holding at rest, this should go up to 13.5+v to recharge.

 

Pierce yea I tested the excite wire it's giving 12v out of it I put a multimeter to it unplugged from the back and got 12v.

As far as self excite when I rev it does nothing it does not change the only volts I see are whatever the battery is there is no jump whatso ever.

 

And these alternators are green on a bench pass

 

check the alternator ground. try this...

voltmeter on DC Volts, put one probe on the battery MINUS terminal, and put the other probe on a cleaned spot on the alternator body, and start the car. with the engine running, more than a fraction of a volt between the grounds means a ground is bad somewhere between battery -> motor -> generator. so do it again with engine ground (on the top of the fuel rail where all the ground wires are screwed) to the alternator ground. make sure you scrape clean the places you probe so they are shiny metal. whichever ground is bad, remove that cable, inspect the cable to ensure its not corroded at the crimps and replace if it is... clean all contact surfaces, reassemble with some dielectric grease.

 

Just did so got a .01

 

ok, check the voltage at the B+ terminal (the big red wire) on the alternator, that should be around 14V when its idling with headlights, AC, etc switched off. it should be at least 13.6V with all that turned on. whatever voltage you see there, should be close to the voltage you see at the battery + terminal, not more than 0.1V difference.

 

hmmm. some alternators have an extra terminal on the back for a radio noise suppression cap.... like this one,



and a 'W' connection for a tachometer (not used in volvos)...

you sure the D+ (tickler wire from the battery light) is on the right terminal ?

 

 

 

Am I on the wrong one?

The Alternator gives the same volts as the battery there at the B+ wire on the alternator thats what I mean in original post by getting the same reading at the alternator post.

 

And yes I know i have the neg off in the photo. I tested everything with the neg on.

 

um, the markings on that are ambiguous. D+ is the smaller screw/nut on the plastic insulator block. that 1st pic, the smaller red lead looks like it is on the + which is meant for the optional noise suppression capacitor.

with the engine NOT running, but the ignition switched on, and the D+ 'exciter' wire connected, said D+ exciter wire should be somewhere UNDER 12V, like 9-10V...

look closely at my picture (lifted from IPDusa or something),



the big nut at 3:30 is B+, the smaller one at 2:30 is D+, the tab at 1 oclock is "+" and the grey block at 11 oclock is that noise surpression thing. W at 8:30 is for a tachometer setup not used on Volvos, the ground screw is on the edge at 7:30, and of course, the regulator brush assembly is at 6 o'clock.

 

So where is the excite wire suppose to be there is no tab other than the one it's on.

And the negative ground to engine should not be on the small one next to the b+ but on the screw it should be on the post at the 7:00?

 

the excite wire goes to D+ whihc is the smaller bolt on the black plastic insulator. you could put a spade lug adapter like this on the screw if you want to leave the pushon spade on the wire.



and ugh, if you grounded D+, I dunno what might have happened to the alternator's guts, this could have fried the diode board inside.

 

I think I found the problem I was following how the guy put the other alternator on before me they hooked the ground to the d+ nut. I just switched out and hooked the neg to the post on the 7 o clock position. I dont have a way to hook the excite to the d+ tho seeing there is no tab there on mine. SO I will have to go get one of those things.

However revved the engine and still no voltage increase over 2500

 

If I did happen to fry the diode board would it still pass on a bench test?

 

i don't knwo what those bench tests actually test for.

you should be able to find a .25" spade lug to screw terminal adapter at a LAPS or electronics store. or take a piece of brass strip, drill a hole in one end big enough for the bolt, cut it off about 3/4" past that hole and snip the sides down to 1/4" wide, bend it 45 degrees or so, put it on the bolt, an d slip your spade lug connector over the .25" wide end thats sticking up... I'd grease it thoroughly with dielectric grease before installing to keep it from corroding.

 

Is laps a auto parts store?