Electric fan install
 

I recently installed 2 electric puller fans on my m103 2.6 and I'm having a bit of a problem, not sure if its wiring or what, but here is what I did and how I have the relay set up:

#30 - Fused to +12VDC disrtibutor block
#85 - one prong on coolant temp sensor, other prong on cts is grounded to engine block.
#87 - +positive wire on fan, -negative wire is grounded to chassis
#86 - +12VDC acc. source.
#87a - Not used.

So my m103 and an unused spot on the next to the original cts, maybe 2 inches more towards the front, so I unscrewed the plug and put in another cts. Using jforgione's idea for the Cool Harness, I ran a 1.1kohms resistor across the terminals so that the fans turned on at 92C. Well, the car gets up to about 80C and the fans turn on. So I removed the resistor and the same thing, fans turn on at 80C. I disconnected the wiring temporarily from both cts on the engine and tested them both with cold engine the resistance was about ~3.45 ± on both. Then I warmed the engine up and they both dropped resistance about the same values so this rules out a faulty cts as far as I'm concerned. So what can I be doing wrong? If I let the car idle for a good while (30-45mins) the needle will eventually make it to 87C mark and sit there for quite a while before temps slowly creep up. Thermostat is fully functional as well.

Nice project .I have been thinking of doing this for some time now. Did you have any problems fitting the fan .And my way would be a simple switch on the dash so i could work it, as , and when , the temp was on the up . I was reading on the web about this guy that new all about the merc engines m103 m102.And his words were to change the thermostat to a lower rating so the water circulated quicker to keep it cool . Can i ask what fan did you use please .And can you post a diagram of wiring .

No problem fitting the fan. However, when mounting them, you should mount one by the lower radiator closet to the alternator and the other at the top of the radiator with the hub of the fan almost centered to the water pump pulley, slightly towards the center. The fans are Spal fans that I got from a 2 different Volvos at the junk yard Looking on the Spal website I'd say the part number for the fan is 30100320, even though it says its a pusher fan, reverse polarity and it is a puller fan, which it what I orginally did as I wondered why my temps kept climbing until I swapped around the positive and negative wires.

First of all, did you use a coolant thremoswitch or a thermosensor? If you really used a thermoswitch, it will have a specific 'on' temperature which is often stamped on the side of the switch. It cant be modified by the addition of external components. If you happen to know the size of the thread and the desired setpoint, I can probably recommend a suitable switch (unlikely to be from a native MB application).

If you've installed a thermosensor, its the wrong component and will never give satisfactory results. A thermosensor has to work with a digital control, not a simple relay. Adding a resistor is just wrong, you're mixing and matching incompatible designs.

One more point. I suggest reversing the 30 and 87 connections. Some will jump on me and insist that 30 should always be +, but no. The reason I like to reverse the + is that when using a switchover relay, 87a will be powered when the fan is off if you wire it 'correctly'. If you wire it backwards as I suggest, it will work normally, but 87a will always be cold, so one less opportunity for a mysterious short.

On my old 2.6 the 2 auxiliary fans in front of the radiator provided enough cooling on their own for everything up to about 110f ambient. All you have to do is trigger them at a lower coolant temperature than stock. I drove it like that for about 30k miles.

I'm using Mercedes A 0085424517 Water Temperature. Sensor. When adding a resistor across the terminals it does cause the fans to trigger sooner by changing the values of the resistance. I have tested this by adding a resistor that significantly dropped the resistance which caused the fans to almost turn on immediately on the stock set up, so I'm sure that the components I'm using are correct. However, there is a fault somewhere in my set up that I haven't figured out yet. I like the reverse set up idea, I may incorporate that.

It will never, ever work the way you want it to. NEVER. You need a thermoswitch, not a thermosensor. The sensor will cause the fan to turn on if it's resistance ever falls low enough to supply enough current to the relay coil to cause the points to close. This will happen at some random temperature, which may or may not be where you want it to be. A resistor will either cause the fan to come on immediately, or not at all. This setup might work if the fan is controlled by the HVAC head unit, which has electronics to turn the fan on based on reading the sensor. But since you are using a simple relay rather than electronic controls, what you need is a thermoswitch permanently set for 92C or wherever.

So what's the difference between my set up and the stock fan set up which uses the same sensor to control the fan? Also, this is where I got the resistor information from: K6JRF Auto Page so not sure why it wouldn't work.

He's right, your relay is not going to work with a sensor, you need an ON/OFF switch. The resistor mod works because the stock fan setup is controlled by the tempmatic unit which is a lot more than just a relay. Heres how I did it on my old 2.6.
http://img.photobucket.com/albums/v2...dashswitch.jpg

Here's how to properly setup a fan relay if you're doing it from scratch. The light and manual switch are optional.
http://www.bmw2002faq.com/applicatio...3af259e129e379

Does this set up utilize the aux fans or did you take out your viscous fan and add an electric one?

I used the stock aux fans and removed the viscous fan. The aux fans on their own provide more than enough cooling for this engine. I was triggering them on high speed with the resistor bypass.

That depends on your climate. Ususally the problem is when its summer and the a/c is on which increases engine temp. At 120F ambient temp with the ac on and both fans on high, if I'm sitting at idle or creeping along slow the temps will rise rapidly. And this is with a new radiator, water pump and running about 80/20 coolant

The aux. electric fans engage at high speed at 105C (about 221F) coolant temp. and disengage at 100C. In addition they are activated at low speed by the AC system high pressure switch if not already running at high speed based on coolant temp. On some modern cars the fans don't engage until about 230F. Most manufacturers have eliminated gages and replaced them with idiot lights because customers complain that the car is "overheating" at 200-210F.

IMO the OE cooling system is very effective, and I think you're better off fixing any problems with it rather than cooking up a home brew solution. Temperatures up to about 110C (about 230F) are normal for extremely hot weather in stop-and-go traffic.

Maximum antifreeze concentration should not exceed 70 percent and 50 percent provides freeze protection down to about -35 F and boilover protection to about 265F (about 130C) with a 15 psi cap while having more than adequate corrosion protection additive concentration.

Water has greater heat capacity than glycol, which is why running over 70 percent glycol is not recommended.

What's the highest temperature reading you're seeing on the dash gage?

Duke

It's 80% water 20% coolant. The cooling system is working and had no issues, it's just that during summers here and using the ac the temp really climbs up if idling or in slow traffic. Actually, now I'm back to 50/50, but after thinking about it, I just realized that the fans switching on at 80°C is irrelevant anyways because there's no coolant even flowing through my radiator at that temp. Thermostat opens up at 87°C anyways, right? I sent mxfrank a pm to get info on the thermoswitch he's talking about.