alternato - PeachParts Mercedes-Benz Forum

martureo · #1 06-18-2016, 08:59 AM

I've got a 603 being put in a s123. Because of the fitment I'm going to run an electric radiator fan as the primary. The current alternator is 70amp. The fans I'm looking at say they max out at a 22 amp draw.

Should I be looking for a higher amperage alternator? What's the minimum I can get away with?

tjts1 · #2 06-18-2016, 09:39 AM

You can get away with 70a but 90a, 115a 150a alternators are cheap and plentiful on eBay. Add an overrunning (OAP) pulley for anything over 70a.

Keep in mind that the alternator only outputs about 60% of its rated amps at idle when you really need that electric fan. So 70a alternator = 42a at idle. 150a alternator = 90a at idle.

Which electric puller fan are you using? There's not many that fit in the space between the om603 and the radiator.

Mxfrank · #3 06-18-2016, 09:41 AM

And dont forget to upgrade the wiring.

martureo · #4 06-18-2016, 09:48 AM

Quote:

Originally Posted by tjts1

You can get away with 70a but 90a, 115a 150a alternators are cheap and plentiful on eBay. Add an overrunning (OAP) pulley for anything over 70a.

Keep in mind that the alternator only outputs about 60% of its rated amps at idle when you really need that electric fan. So 70a alternator = 42a at idle. 150a alternator = 90a at idle.

Which electric puller fan are you using? There's not many that fit in the space between the om603 and the radiator.

It's going to be a pusher. There just isn't any room for a puller.

Mike D · #5 06-18-2016, 10:01 AM

Be sure to use a voltage relay on the fan. Don't try to power it from the existing wiring.

I run 16" cooling fans on my W114's using the stock 35A alternators with no problems.

What kind of monster fan are you using which pulls 22 amp? My 16's only pull 15-17 amps.

You will need at a minimum 12 gauge wiring and I'd recommend 10 gauge to provide adequate current.

Mxfrank · #6 06-18-2016, 10:02 AM

I dont know how much room you have, but Spal 30100400-1 is an incredible 2 1/16" thick, designed for tight spaces. Pullers are more efficient than pushers. You derate CFM's by 15% just by flipping the fan around.

tjts1 · #7 06-18-2016, 10:02 AM

Quote:

Originally Posted by martureo

It's going to be a pusher. There just isn't any room for a puller.

From my experience I don't think a single pusher fan is going to be enough. I found a dual puller fan setup with shrouds from a Toyota that is 2.5" thick. It fits the W124/OM603 with room to spare and I use it in conjunction with a smaller pusher fan. I don't know if the 123 engine bay is bigger or smaller. The 2 pullers draw about 30a combined.

BillGrissom · #8 06-18-2016, 06:12 PM

Check the H.A.M.B. website for hot rodders (www.jalopyjournal.com/forum). Many use a Ford Taurus 2-spd fan. The fan current ratings probably refer to initial start-up draw, so you can size a relay that won't burn up. Steady running current is probably less. Also, the fan doesn't run continuously. No need for an alternator to meet peak load since your battery is a great "ballast". If your battery stays charged over a week, the alternator is doing its job, but others disagree.

tjts1 · #9 06-18-2016, 06:19 PM

The Ford 2spd (aka Volvo fan in a different shroud) is about 4.5" thick.

Zulfiqar · #10 06-20-2016, 10:37 AM

when using an overly powerful fan - its best to either use a PWM controller to run it or make a 2 stage setup to start it slowly with a resistor so you dont weld your relay contacts if you try to start them at full power directly.

The old taurus fans are nice and powerful, so are old nissan altima fans if you are scouring the yard for a set of fans.

Diesel911 · #11 06-20-2016, 12:49 PM

The little Relays and the Sockets are cheap on Ebay.

The Relays look similar but come in different amperages. The Wiring for them is easily found by doing a image.google type search.

There is also single and Double fan wiring disgrams and diagrams so the Fan goes on when the AC goes on.

funola · #12 06-20-2016, 01:19 PM

Quote:

Originally Posted by martureo

It's going to be a pusher. There just isn't any room for a puller.

I am testing an upgraded pusher fan (16" dia. from a 560 SEL) on my 85 300D as the only fan for both AC condenser and engine radiator cooling. I added a temporary test shroud made from cardboard in front of the condenser and with that, it is keeping the coolant temp gauge within reasonable numbers (85 to 90 C) with ambients up to 85F. I am waiting for hotter days to come to see how it performs in 90F and above ambient.

I have the stock 65A alternator. At idle and the aux fan and blower running, charge voltage is 12.5 V, i.e. = not charging. Once I start driving , charge voltage goes up to 13V, i.e. charging although lower than the 13.4 V if both fans were off. If the car is idling in city traffic most of the time with the AC on, the battery may run down, otherwise it may be just fine.

I may try modifying the regulator to get a higher charge current at idle, or upgrade the alternator to a 115A unit, if tests shows that it is necessary. Or leave the 65A unit, if tests shows it is sufficient.

Hit Man X · #13 06-20-2016, 04:53 PM

My 603 and 103s use 150A (or is it 143A?) from W140 gasser V8s. I think the 400E came with a 120A alt.

tjts1 · #14 06-20-2016, 05:39 PM

Quote:

Originally Posted by Hit Man X

My 603 and 103s use 150A (or is it 143A?) from W140 gasser V8s. I think the 400E came with a 120A alt.

I just installed a 150a alternator from an R230 SL on my om603. If I switch on every electric load (E fans, lights, cabin fan, defogger etc) I still have 14.2v at idle. $45 for the alternator, $15 for a new voltage regulator and $28 for the over running pulley all on eBay. Bargain in my book. The voltage regulator on it has some neat features built in like soft start and anti stall.