Alt not increasing voltage at idle!

[Dictator 39]

Hello i have a 1992 volvo 240 wagon upgraded my amp from a aq 2200d to a Cresendo bc 3500d.

Ordered a 275ohio alt was working great for 2months then stopped working sent it back to ohio had the alt looked at by the technician said it was working fine.

Installed it again and started doing this weird voltage thing with my batteries. Voltage of batteries is 12.8 with car off when i turn the car on the voltage stays at 12.8 does not increase inless i tap the gas and it jumps to 13.8volts

Why am i recieving no voltage increase when the car is turned on, which makes me think im getting no idle amp output.

I did not upgrade any wires on the alt all factory. 55ah yellow top upfront and 35ah yellow top in the back.

Inatalled the new cresendo and a Mb Quart Q.125 4channel drained the battery down to 60% inless then 30mins of beating.

Why are the batteries draining if this alt is supposly 275 amps.My fail or the alt fail?

Edited July 11, 2011 by Dictator

[reelfish92 54]

I have had my Ohio Alt. in my yukon for a while now, never had that issue. Keep the voltage up by keeping the RPMs up. Ohio should have sent you info on the alt. what it tested on the bench at a certain amount of RPMs. Im at 14.4v at idle, so I keep it up by keeping the RPMs at 1000-2000 RPMs.

[ford302redneck 15]

The alternator doesn't have enough output at the idle RPM of your car, that's why when tapping the gas raising RPM and producing more current.

Just because its rated at 275, doesn't mean it puts it all out once you start the engine. Most alt's only put at around half output at idle unless its designed around a lot of output at idle, usually the top end output is cut from this. Basically you can't have a ton of output at idle then a lot more at higher RPM. Either a lot at idle and a little more on the top, or a lot of the top, with less at idle.

Also, alternators have a "cut on" RPM basically. This means below a certain RPM the output is very low, then once it hits the right RPM, it starts producing alot more current.

So, it has nothing to do with the companies alt, but more to do with your cars pulley setup and or idle RPM.

[Dictator 39]

Batteries where still Discharging more then the alternator was putting out going 40mph down the road.Think bigger battery bank would help the charge problem?

[Dictator 39]

I have had my Ohio Alt. in my yukon for a while now, never had that issue. Keep the voltage up by keeping the RPMs up. Ohio should have sent you info on the alt. what it tested on the bench at a certain amount of RPMs. Im at 14.4v at idle, so I keep it up by keeping the RPMs at 1000-2000 RPMs.

Spec sheet states alt turns on at 2182rmps. 66amps at 2500rpm's 269amps at 6000rpm.

Edited July 11, 2011 by Dictator

[Julian 641]

Holy shit, most cars idle at 900-1k rpms. 2k for me is highway speeds.

[Sir-Lancelot 216]

Ouch.

My truck idles at 550 rpm.

Does your Wagon even rev up to 6k rpm? That's fucked up Bro.

[Dangrebel 89]

I think it means alternator rpms if so I can vary by belt speed and pully size it always rotates faster then the motor

[Dictator 39]

I think it means alternator rpms if so I can vary by belt speed and pully size it always rotates faster then the motor

...So your advice would be a smaller belt?

[shizzzon 461]

ALL ALTERNATOR SPEC SHEETS are rated at ALT rpms, not engine...

It is up to the USER (unless overdrive pulley comes with alt) to know what the ratio of crank to alternator is.

a 3:1 ratio means 800 engine is 2400rpm alt.

[Dangrebel 89]

I think it means alternator rpms if so I can vary by belt speed and pully size it always rotates faster then the motor

...So your advice would be a smaller belt?

No sir a smaller pulley would help.

[Sir-Lancelot 216]

ALL ALTERNATOR SPEC SHEETS are rated at ALT rpms, not engine...

It is up to the USER (unless overdrive pulley comes with alt) to know what the ratio of crank to alternator is.

a 3:1 ratio means 800 engine is 2400rpm alt.

No shit, Didnt even think of that but your right.

DOH!

[Mason858 0]

More batteries cant hurt

[Dictator 39]

Ok went for a icecream stop and alt started shitting on me going 40mph down road. Wonderful alt bass was at zero was only screaming the mid's highs and the both batteries went below 50%.

Edited July 12, 2011 by Dictator

[Dictator 39]

Purchased the alt in April used it for 2months then started to screw up on me and not charge the battery properly so i sent the alt back to Ohio since it was under warranty. My technician "Supposedly looked it over and found no problems at all with the alt hmm...weird because on my end wasn't producing nearly anything to charge the battery. The technician sent it back with a tech sheet of him testing the alt on a machine. Hooked the alt up turned the car on and voltage never increased. Sent some rpm's from the engine to it jumped to 13.5volts but wasn't putting out any amperage at all, even going 40mph down the road it wasn't charging fairly enough. Which makes me come to this conclusion. The "Diode trio"s are bad in the alt if anybody knows anything about alts that's not something you want to go wrong inside it since its a bish to fix by the technician ,what i found from research. No voltage increase at idle and low amperage output sounds right on point to the problems im having......Taking the alt to professionals in are city to diagnosed it to make shure.

Not 100% shure if that's the problem but im going to get a expert to check the alt over.

Really good write up straight to the point.

Edited July 12, 2011 by Dictator

[MECHMAN 8]

My 240 isn't running the stock alternator so I can't measure pulley dia, but if you measure crank pulley dia and your alt pulley dia you might find that at idle you are running below the turn-on speed.

What RPM is your idle? How about cruise RPM at say 40mph?

As for the 40mph cruise issue, that could be in the alternator design.

It could be a poorly designed alternator or it could be your rotor speed is low. Not all alternators are created equal, many of the 270a units out there are nothing more than a stator upgrade and won't pull the advertised power down low.

If you are done with your warranty and want someone to check it out for you I would be happy to bench test it and inspect it for nothing more than the cost of your shipping. Then if it's not performing up to spec we can advise you on what needs to be done to the unit to get it up to the task.

I'm always willing to help out a Volvo owner, my autocross car is a 244 and I have owned several. Just sold my 245 2 months ago and I am looking for another for a good audio build.

[djjdnap 78]

take it to autozone or oreilly and let them test it for you.

it wont show current, but it does test the diodes and if its good or not

[Dictator 39]

My 240 isn't running the stock alternator so I can't measure pulley dia, but if you measure crank pulley dia and your alt pulley dia you might find that at idle you are running below the turn-on speed.

What RPM is your idle? How about cruise RPM at say 40mph?

As for the 40mph cruise issue, that could be in the alternator design.

It could be a poorly designed alternator or it could be your rotor speed is low. Not all alternators are created equal, many of the 270a units out there are nothing more than a stator upgrade and won't pull the advertised power down low.

If you are done with your warranty and want someone to check it out for you I would be happy to bench test it and inspect it for nothing more than the cost of your shipping. Then if it's not performing up to spec we can advise you on what needs to be done to the unit to get it up to the task.

I'm always willing to help out a Volvo owner, my autocross car is a 244 and I have owned several. Just sold my 245 2 months ago and I am looking for another for a good audio build.

Yup still underwarranty only had it for 3months. I appreciate sir, going to try to fix it with the local alt place and see what they say. Still will take in account of your offer thats really cool of you to go out your way and help out a fell volvo owener

3Volvo's in are house hold

[Dictator 39]

take it to autozone or oreilly and let them test it for you.

it wont show current, but it does test the diodes and if its good or not

Just had the alt tested at advance. Diode's are fried in the alt. That's good customer service sending faulty unit back even though it was suppose to be repaired.

[MECHMAN 8]

Yup still underwarranty only had it for 3months. I appreciate sir, going to try to fix it with the local alt place and see what they say. Still will take in account of your offer thats really cool of you to go out your way and help out a fell volvo owener

3Volvo's in are house hold

When this unit goes out of warranty I do offer rebuild services at a very reasonable cost.

Just had the alt tested at advance. Diode's are fried in the alt. That's good customer service sending faulty unit back even though it was suppose to be repaired.

If you are going to have it fixed locally be sure that they use the higher capacity diodes, many local shops will stick the stock style rectifier in there and that will not last long.

[Dictator 39]

Yup still underwarranty only had it for 3months. I appreciate sir, going to try to fix it with the local alt place and see what they say. Still will take in account of your offer thats really cool of you to go out your way and help out a fell volvo owener

3Volvo's in are house hold

When this unit goes out of warranty I do offer rebuild services at a very reasonable cost.

Just had the alt tested at advance. Diode's are fried in the alt. That's good customer service sending faulty unit back even though it was suppose to be repaired.

If you are going to have it fixed locally be sure that they use the higher capacity diodes, many local shops will stick the stock style rectifier in there and that will not last long.

Thanks for the advice.

[ford302redneck 15]

Who are you using locally?

Honestly, I would get a quote from Mechman, and try to go that route if possible. Even if it cost a little more and without a alt for a few days, it will be well worth not having to worry about it for a good while.

[MECHMAN 8]

^^^ Thanks!

He PM'd about this earlier, we will be taking good care of his unit.

[Sir-Lancelot 216]

we will be taking good care of his unit.

Wait!

I thought we were talking about alternators here.

Bwahahaha!

Sorry, you made that way too easy for me.

[Ohjay 116]