Hi everyone, I'm a newbie here and haven't posted much. I have a nice clean '92 940 non-turbo that has been sitting in my parent's house for a while. I used it as a daily for a couple of months and loved the luxurious interior and smooth ride. Aside from a rad pipe leaking it gave me no problems.

It always had a slightly weak alternator back then, as it would turn over slowly, but never stalled and always started. Then the alarm system, which seems to have been installed in the early 90s, started draining the battery, so I snipped it. My brother used it for a while and told me it kept stalling, so I figured the alternator was finally toast, I checked everything with a voltmeter and it seemed to be weak, so I figured I would change it with a Denso unit I got from FCP. After changing the alternator it ran for about 15 minutes without stalling and the battery seemed to be getting more juice from the alternator, so I thought the problem was solved. When I went to start it again though, I got nothing. The battery was flat. Any ideas? I'm useless when it comes to electrical problems, so maybe it's something obvious... any help would be appreciated!

 

Battery might not be holding a charge. Take the battery to your local auto parts store and have it tested for free.

 

I tried switching to a battery that definitely works, no dice.

 

So do you have a crank / no start situation.... or a no crank / no start situation?

You need fuel... compression... spark for it to run.

http://www.stepbystepvolvo.com/NoStart.html

 

I have a no crank no start. First battery was completely flat, second one, pulled from a working car, had dash lights when the key was turned to position one, but then died after a very short crank when I tried to start.

 

Take the better battery out and get it tested and fully charged.

 

If you have a for sure fully charged battery... and it still won't crank I'd start thinking about the starter. Especially since you mentioned "
slow cranking" in your original post.

Also make sure all your connections at battery...alternator....starter are clean and tight.

 

Alternators don't get weak. They should measure at the battery in normal idle mode anywhere between 13.6 V to 14.2 volts. If in that range there is nothing wrong with the alternator. If the starter turn slowly and draws a lot of current in start mode I would suggest looking hard at the starter.

 

a bad ground from the battery to the chassis could cause charging AND starting problems. easy test, fully charge the battery first, then put a DC volt meter between the battery - terminal, and a good engine ground like a valve cover bolt... have a friend crank the car. if you see any more than a fraction of a volt, it be time to debug why.

 

YousefTak, also check to make sure that the small red wire with a spade fitting on the end is securely attached to the back of the alternator. This wire sends a charge to the alternator to "pre-excite" it by setting up a magnetic field to allow it to charge at a relativly low RPM. Without this connection, it takes about 3500rpm to start the alternator charging.

 

Hey everyone, thanks so much for the input. I've had zero time to get back down to my parents' to try anything, but I'll be sure to report back when I do in the coming weeks.

 

So I finally got the battery tested. It seems that it was not holding a charge so I replaced it. Seems to have done the trick although I now have a constant check engine light (it was intermittent before I changed the battery and alternator). I'll have to check to see what the code is. Thanks for the advice!