i found the problem!!!, i hope?

[jeff5347]

Okay so i posted the other day wondering if i may need a new alt or what could be the trouble. Stated before only major stuff i have is a msd 6al with msd 85551 dist, black magic fan which draws about 20 amps, cassette radio, headlights and int lights Pretty much thats it. I did the MAD headlight relay but with the current alt which does about maybe 63 amps didnt see much diff. So i started to wonder, what makes my voltage drop when the lights and fan and radio are going. Did some testing. While car running and everything was off tested 3 places, The back of the alt, the batt itself and the horn relay.
1. No electrical power assc. running at all. in all 3 places read 14.2-14.3 (dont have a voltmeter just an autometer volt gauge)
2. Headlight on (one disconnected) Again in all 3 places about 13.5
3. Connect the second headlight... all 3 13.2 or so
4. radio on, headlights on, and now the fan on all 3 maybe 12 volts.
So now i wonder and help me out. My thinking is that the Alt does not produce enough amps to power these 3 measly items and help keep the batt at a full charge. Even if starting to rev the engine the gauge moves maybe .1-.2 but not anymore.
(also to note watched the volt gauge in the car and saw same readings as with the external volt gauge.)
So after this long winded post am i correct in thinking my alt is the culpret. Just not tough enough and maybe i should try a 105-140 amp alt.
Im going to try putting a relay on the fan to se if this helps also. Any thoughts? Please.....?

[Madspeed]

the relay Isnt going to do Sh@# for you
A relay is an electrical switch nothing more
I would use a relay on a fan but not for your reasons.
go get one of those hayden electronic adjustable fan and relay setups It is a small compact unit not the gawd awful huge mechanical one with the metal capilary tube, Im talking about the little black one about 2"X1" with the relay built in and install it per instructions. its all explained in the instructions you can get this at allmost any auto parts store like pepboys

Now as far as your voltmeter being low?
You answered your own question
your alternator can't put out enough amperage to keep up with everything and that is why your dropping down to 12 vlts
Go get a new higher amp alt try one from a diesle car or truck they usually put out over 100 amps or a police car or taxi they are all heavy duty alts

I bought one for my 72 blazer from an olds diesle car I forget what year but If you want I can try to go find out the number of the alt
and i got it from Autozone for under 100 bucks with a lifetime warrenty
Just PM me if you need help and ill give you my cell umber Ill steer you through it if you get lost

Gl Ken F

[GetMore]

Definitely a weak alternator. On the other hand it looks like you have a decent electrical system.

Something to keep in mind: Alternators trade their voltage output for amps. In other words, when there is low load they put out higher voltage. When load goes up they put out more amps, but the voltage drops.
The larger the alternator, the more power it will put out at idle.

Your car was not expected to run much electrical equipment. Electric fans are a big addition to it.

Adding a relay for the fan will not drop it's power draw, so it's not going to change anything with your voltage.

BTW, to check to see if you need the relays for the headlights try checking voltage at the headlight.

[jeff5347]

hey Guys,
Thanks for the replies. I am on the same track with you as i had done some digging yesterday,. Checked my connections and grounds and everything is is good shape. Batt is in trunk grounded to the inside bumper bolt with a 2 gauge wire. Also have a copper ground wire from the block to the firewall. chaeck all the wires i have run and everythinbg is nice and clean on good grounds, no cracks in the wires and such. On to what you guys had conveyed to me. I did do the relay for the fan but found out it already has one built in to it, and guess what. No diff, maybe .2 volts if anything. rewired some things with heavier gauge wire also as some stuff was a little small. Not much difference. So all in all i think like you all stated. The alt cant keep up. not tough enough. Here is a question curious on. I was talking with my father who is a mechanic and said that GM alts get hot and arent to great. Sid to try a late model nissan or toyota alt. He is into Nascar as i am and states they use foreign alts on the racecars. Any thoughts on that. My only thought is the mods to fit a foriegn alt would be a little much for the desired results. Is this a good idea, bad idea? Any thoughts?

[Madspeed]

They do it because the alts are tiny and liteweight no because they put out a lot and they have a smaller internal rotating mass

Its not for you bud, go with a reg highoutput gm style alt

[jeff5347]

Cool Madspeed,
Thats kinda what i thought. Just a curious question,. I see you have a good amount of infoon the electrical forum. is that your area of expertise. Again thanks. Gonna get the 100 or 140 amp alt and pray i see that gauge never flucuate. Thnaksd for everyones help.

[Madspeed]

There are Guys here that could work circles around me in electrical.
But I like to think I have a good grasp on it.
I am all self taught ,As in when I was younger and blew a sterio or amp I would find the answers and tests i needed and fix it

I find electrical the most challanging and allways took those jobs in my career in the auto feild

Im just trying to share my limeted knowladge and ease some of you fellas frustrations.

Jack of al trades Master of none =)

Ken F
Edit if you get the high amp alt you should be fine, your guage might move when the fan comes on and climb back up
turn everything on lights high beams hazzards Wipers on high heater (ac if you got it) interior lights and make shure the fan is on , raise the rpm to about 1500 2000 and check vltg at the batt it shouldnt go below 12.5 and not above 13.7 ish 14 vlts will boil the water out of the battery