Hello fellow volvo brothers/sisters

I have been having issue with my voltage on my car.
Sometime it will read 12+ volts on my meter and the car runs great and other times when im driving my voltage drops below 12 volts and the car runs like crap.
There is a new alternator in it from crappy value and a new battery,i also check all my ground and battery terminals and everything looks good.

What are your guys suggestions?

What series car?

+12v distribution block? Are your headlights on or off when the volts drop?

Edit - if this is on the '84 240, you've got a few things to look at. First one is the voltage distribution block by the battery. It can get scuzzy. Next is the fuse panel - it gets really scuzzy sitting down there by the moist carpets and such.

240s have crappy wiring that are saved by their relatively low current draws. Add age and/or higher power devices and you can have some problems. ALL the power for the car goes through simple little spade connectors, which don't have a huge contact area. If they get a little dirty, they just create heat the more current they're asked to pass. This can occur at the voltage distribution block or at the back of the fuse panel. The fuses and fuse tabs get really nasty too, and many problems are solved (and detected) by rolling each fuse in it's tab. If one's hot, you've got a current problem right there. Another good indicator is if your headlights are on and you hit your turn signals and your voltage gauge jumps 1-2 volts in time with the blinkers, you've got a voltage supply issue.

ALL the power for the headlights goes through the fusebox and the (susceptible to failure) headlight switch too, so it would be a good idea to bypass that by adding a pair of relays - one for high beams, one for low. Use the power from the high/low relay (basically, what goes to your headlights) to trigger the new relays, and power the new relays straight from the battery through fuses or (even better) circuit breakers. That saves up to 35 amps of power (with, upgraded bulbs) running through your fuse box and headlight switch! You'll be amazed at how much more voltage is available for things like fuel pumps and heater fans. While you're at it, rewire your headlights to come from an area on the fuse box that's only on at position #2 of the ignition switch.

so do you think that the alternator is not the culprit?
I do have an extra alternator that i will try tonight,but if that does not work i will try your suggestion

Thanks

yes this is of the 84 240.

how do you know what i drive!!!

I looked in your profile and in your most active topic you mentioned that car.

It could be the alternator, but it might not be. You said it was new and that your grounds & battery connections looked good. If the alternator is working properly and your battery is indeed getting +13.5v while the engine is running and various devices are on, any voltage drop will come from the places I mentioned. The fuel pumps, ignition system, and lambda & idle computers are all run off the fuse box, as are practically everything else. I took a shot at your problem without asking for clarification.

So for clarification:

What "meter" is this that you're getting your readings from?

If it's a DVOM (handheld digital volt meter) where do you have it connected?

Have you checked the voltage drop from the battery to the fuse box? Connect the red wire of your DVOM to the battery positive terminal and the black wire of your DVOM to the device side of any fuse, and load it up. If you get any voltage reading that number is the amount of loss you're getting on that circuit. I would accept no more than about 3/4 volt on a 30A circuit, fully loaded. To find the device side of a fuse you just have to pull the fuse and check which side has volts and which side has none - the one with volts is the battery side and the one with none is the device side.

What devices do you have powered when you see less than 12v, and what happens when you turn on some of the higher load circuits?

How low does the volts have to get before the engine starts running funny?

found my problem.It was a dead alternator