I just swapped out my alternator and my voltage guage still jumps when under load. Maybe because the battery might be getting weak or whatever. My question is is there a high output swap option. Example a bolt on volvo to volvo swap or for my 4runner i can run a cadillac 130amp alternator after buying a swap harness plug. Is there something i can do besides going fully custom with a big chevy 3 wire and having to wire that in.

 

what is it jumping around between ? voltage gauges weren't standard, where's yours wired to? directly to the back of the generator, or across the battery, or the ignition switch output, or what??

whats the requirement for this high amp generator? the stock one on the later cars is around 100A, the wiring in the car is sized for that, 100 amps is a LOT of current to dump into a battery if the battery is discharged.

any car battery / auto electrical place will test your battery for free hoping they sell you one if the battery is weak/bad, replace it, don't beef up the alternator hoping to compensate.

 

It's definately a stock volvo voltage gauge. My 240 calls for either a 55 amp or 70 amp. Atleast thats what the autozone website said. I want it for a stereo system and maybe some aux lighting. Im sure that the battery is kinda weak. The gauge is jumping under load with turn signals or wipers on while im idleing. when i just have head lights heater and radio on the voltage drops way down. I dont have any stereo equipment in it right now but would like to soon.

 

what year is this 240? (I have wiring diagrams for most years). sounds like an older one if its just 55A or 70A (my bleepin' motorcycle has a 50A...)

my guess is the voltage gauge is connected to the circuit 15 output of the ignition switch, and a ground somewhere in the dash, and if there are dirty connections, or your battery is weak, yeah, its going to bounce around 1/2 volt or so, and sure, at idle, the alternator can't even output its rated 55 or 70 amps and its voltage will be low with high current loads like headlights (4-5 amps each)

I wouldn't go overboard with a bigger alternator... Note that a 100A at 14 volts takes nearly 2 horsepower to spin. Whatever non-stock thing you install, you'll probably have to fabricate brackets for, you'll be putting more strain on the belts, etc. My guess is, the easiest fit would be the 100A from a later 240/740/940. But, first get a GOOD new battery, maybe even go for the larger size that fits in many 240's (it was used on the diesel versions).

The correct battery for all my volvos (87 240, 92 740, and a couple other 90's models) have a 'flange' at the bottom thats clamped down to hold the battery securely in place. Another thread on here suggests older 240s used a group 46, which is NLA, and if you adapt a group 47, you need to lengthen the cables because the terminals are swapped.

when you say stereo upgrade, do you just mean a modern head unit with some decent speakers powered off the 50Wx4 or whatever head's built in amps, or do you mean some kinda monster competition system with a half dozen high power amps, earthquake grade subwoofers, etc ? for sure if you're going with big amps you'll want to use a bank of those 'super capacitor' things to buffer the power, and yes, you'll likely need at least a 100A alternator.

 

It is an 82. I figured that I would have to fab up some sort of brackets. Im not going to do a competition grade stereo. Right now it has a alpine head unit 50x4 on the watts. the only speakers that i have in it ar the stock ones in the door. I eventually want to run same wattage on the head unit but a much nicer one with the door speakers and im going to put 6x9's in the rear window. I will probably run those with a 400 watt 4-way amp and 2 12"s in the trunk on anywhere from 1500-2000 watt amp. I do know that i will need a power cap but I think iwant to run a dual battery in the trunk in stead of a power cap. A battery is cheaper and will hold more power.

 

a good 50Wx4 modern deck will easily run 6x9's (or my preferred 6.5" rounds) at serious volume levels, loud enough to damage your hearing in the confined space of a compact car.

dual batteries that aren't exactly matched and side by side require a RV style charge isolator/controller to deal with the inherent inbalance. Don't just get the cheap relay kind, you want the solid state one or the weaker battery will discharge the better one.. and you'll need to run a 100A wire back there from the alternator to this second battery (plus, all the stereo cabling, you'll probably need 5-6 RCA cables (front, rear, sub) plus speaker wires to go from that amp back to the front speakers)... Suggestion, run all this along the passenger side of the transmission hump, remove the passenger seat, rear seat, and both passenger side door sills, lift the carpet so you can get the wires under there. Tape the wires down so they lay flat against the lower side of the tranny hump, then lay the carpet back down, replace the seats etc..

 

naturally, 82 is one of the few years I *don't* have wiring diagrams for (my collection is missing 81,82,83)

phew, 1980 had the old external relay-style voltage regulator instead of the integrated solid state regulator. 84 has the modern 2-wire (+ground) alternator with an integral regulator.

the '84 diagram shows the volt meter connected to fuse 13 (power in run) which also energizes the coil to the fuel pump relay (later years, the fuel pump relay is energized by the ECU when it detects the engine is turning over). so, dirty contacts on the 'positive terminal', or a worn out ignition switch, or a corroded fuse 13 could cause sufficient voltage drop at that meter to make it twitch when circuits are switched on/off. SOME twitching is totally normal, especially with the headlights at idle RPMs.

 

My alternator is internally regulated. It's the same one that my 87 had i believe. It looks exactly the same. My battery contacts are all clean and my ignition switch is new. My gramps replaced it because it wouldn't release the key from the start position you had to move it back from start or it would just sit there and crank. Im positive that my battery is just weak. The battery say in another car for a while that wasn't getting driven until i got the volvo up and running again. So what year 240 would i want to look for that has that 100 amp in it.

 

The alternator in my 1992 740 is 100A. in fact, I think the alternator from a 1987 240 might be ... errr, no, that one is 70 or 80 amp. hmm, looks like the later 240s all got 80A.

catch22, on a 740/940, the alternator mount is rather completely different, its on the other side of the engine where your distributor is. the 740/940 have the distributor on the back of the head coming off the camshaft.

 

I like the idea of running the wires next to the tranny hump. I was going to grab a battery isolator from a old ford or chevy and run it that way.
Other idea was to just wire it like a power cap and run a cable from bat+ to bat+ and ground the second battery in the trunk. Then wire my amp and all that to the battery in the trunk. I got the wiring of the stereo stuff in the bag. I can do that no problem. Just wanted more output of an alternator since apparently alternator shops no longer rewind and beef up alternators anymore.

 

hmmm Maybe ill just make it work till i build my engine then it will have the 100 amp on it already.

As far as a stock deck running the speakers, it has been my experience that the speakers tend to start sounding distorted if you buy ones that are made to be ran from a deck ie a higher wattage. Im going to do it all the right way. I dont like having to pull stuff out to redo it how i should have the first time you know what im saying. Im going to buy my speakers and deck with the intention of running 2 amps so i have to find a deck with a sub control as well as front and rear rca's on it.

 

if you do the + to + thing without an isolator, that wire should be as short and heavy gauge as physically possible (at least as heavy as the existing battery to starter wire), and VERY IMPORTANT, both batteries should be brand new and absolutely identical, or the stronger battery will discharge into the weaker one which will do neither of them any good. It would make a fair bit of electrical sense to run that wire from the starter + terminal rather than from the existing battery +


oh. the 100A alternator in my 740T, the mounting bolts are 120mm center to center, and the top mounting bolt which is the pivot is 95mm from the alternator axle centerline. I couldn't get my caliber in there to measure from the other mounting bolt to the centerline but I think its the same.

so if your alternator mounts are 120mm apart, then they should be interchangable. I *highly* recommend getting the poly alternator bushings from IPDusa (or whatever) when you swap alternators, they last much longer. if the pivot-to-alternator-axle center to center is also the same, then you can probably use the same size belt

 

Awesome thanks for the info. My issue has progressed. This morning on my way to work my voltage started to drop and wouldn't come back up with RPM's. I started at around 14 when i left for work 15 minutes later it was down to about 12 and when i got to work it was holding around 10.5-11 it wouldn't go up when i pushed on the gas. Weird thing was that my lights weren't going dim or anything. Im going to go out on my first break and put a multimeter on the battery and see what i get ill let you know. Here are the pics of the gauge. Do you think it could just be a 30 year old gauge that may be going out?


One pic is half way to work when it was around 12 volts other is when i got to work and it was way down. dont worry about the oil pressure the gauge is messed up.

 

So i went out and checked the voltage. 12.55 just sitting there. 12.14 after i started it and it stayed the same and didn't move after hitting the throttle and holding it for a few seconds no change. When i go out to lunch im going to start it and pull off the neg battery cable and see if the alternator is working and just not charging the battery or if the brand new alternator is actually a P.O.S. out of the box. It just sucks that they don't stock the damn thing and it takes days for it to come in.

 

sounds like either a bad alternator, or perhaps the D+ circuit isn't connected correctly. WHen you first turn the key on, does the BATT/ALT red light come on? if it doesn't, either the BATT/ALT bulb is bad, or the D+ wire (usually a skinny red wire) isn't connected properly. This circuit is required for the alternator to get 'bootstrap' current so it can start alternating.

when you start the engine, does the red light go out (some cars, you have to blip the throttle to turn it out). if the light stays on, the alternator isn't generating any juice (or the D+ wire is shorted to ground somewhere?).

 

oh, do NOT run the car with the battery disconnected, that can fry things.

 

Light stays on after i start it. It wasn't on when i left for work. it came on slowly as i was driving to work. They sold me a ****ty alternator. II went out started it and pulled off the neg cable and it died immediately. So it's not generating anything. The next new one is on order and should be in tomorrow afternoon. Im going to pull it out when i get home and ill double check that the little wire is connected. I think i had to repair that wire at one point in the cars life because there is a butt connector on the wire. It also had some bare spots on it when i put the alternator in so i electrical taped it so there wasn't anymore bare wire showing

 

electrical tape doesnt' last very long under the hood.

I would instead follow that wire as far back as you can, and splice a fresh piece of proper automotive grade hookup wire to it.

 

It just needs to last a couple months

 

Did you take any of "fail" alternators to be tested at a auto parts store?