Layout of relay tray? '93 E250 Euro - PeachParts Mercedes-Benz Forum

LCA078 · #1 07-24-2010, 12:37 PM

I've searched the forum but can't find a layout of the relay tray for my 93 E250 euro-spec 2.5L TD. To get to it, you have to remove the fuse cover up by the driver's corner of the engine bay. I'm assuming it's the same as a 300D 2.5L layout as just about everything else matches. Anyone know of a pic that tells me which relay is which? There is no legend card like the fuse box.

Jeremy5848 · #2 07-24-2010, 01:30 PM

Try this. It's from the 1986-1992 W124 ETM (USA). It should at least be similar to your Yurro-spec model. Note that the relay diagram actually shows the sockets, not the relays. Thus, there are three boxes marked "K" because the light-out warning module is huge and uses three sockets for all its connections.

Jeremy

LCA078 · #3 07-24-2010, 02:23 PM

Jeremy- you're saving me lots of time! Thanks.

Since there are two aux fan relays, I'm assuming the B-preresistor relay is for high speed and the C relay is for low speed (as it incorporates the resistor in the circuit. Am I right on this? Still can't get my aux fan to turn on but it's more a little more complicated because I don't have any freon in my system (bad compressor was removed a couple days ago). Don't quite know how to duplicate the system logic by opening this switch/shorting that one that turns on the aux fan.

Well, I'm done playing with my car today and I'm off to bars for some vino.

Jeremy- I see you're from Sonoma country which I assume is the California Sonoma. I used to live in Los Altos near Stanford and really enjoyed the Bay Area- especially my trips north towards you. I have to say, though, that living in Italy kinda trumps the Sonoma/Napa regions in the overall experience. But hey, what do you expect, it's Italy!

Thanks again for the quick replies.

Jeremy5848 · #4 07-24-2010, 04:51 PM

I've only been in far northern Italy (southern Switzerland, if you will) but I'm sure you are having a good time. Yes, I am just south of Santa Rosa in Sonoma County after 25 years in Santa Clara as a slave of the semiconductor industry.

The two relays are indeed for high and low speed. Low speed is triggered by a pressure switch in the air conditioning refrigerant line near the thing with the sight glass (left front of engine compartment, behind the headlight). The resistor is in that same area. You should be able to short the pins of that switch and the fan will come on (ignition switch must be on, engine does not have to be running).

High speed is triggered by a switch in the water jacket, up near the secondary fuel filter. As built, the switch trips at 105C (blue plastic top on switch, three pins in switch). There are three other varieties of this switch with other colors and temperatures. You should be able to short the pins that have a two-pin connector on them and the fan will run in high speed.

If neither will make the fan work, listen for the relays, they should 'click,' and check all the fuses (fuse 7 for the relay coils and fuse D for the load -- the fan). If the relays 'click' but the fan does not run then a wire or connector has failed or the fan is bad. There are no fuses in between the relays and the fan, BTW.

The resistor is made of a wire resistance coil with a ceramic case and a metal bracket to bolt it to the inner fender. It usually does not fail but the wires, connections, etc., could be damaged. This will affect low speed only.

Jeremy

LCA078 · #5 07-24-2010, 07:50 PM

Sounds like I have some easy tests for tomorrow on my fan circuits. I'll post what I find.

I myself worked in Santa Clara- at the corner of Bowers and Central Expressway-for a little semiconductor company. You might of heard of it- Intel. That was until 2003 when the Army decided I was better suited in a cockpit and I became a mobilized reservist. After multiple deployments, I was too out of date with semiconductors so I found this nice little Army job in Italy. Maybe one day I'll make it back to California.

As for the Eye-taly, well, the Texan in me has a hard time letting go

Jeremy5848 · #6 07-24-2010, 08:59 PM

One of my good friends at Intel in the 1990s was Dave Ferguson. Ham radio operator, wheelchair-bound due to an accident, Dave was one of the designers of the Pentium microprocessor. He could point to the drawing and say "I did that part." He retired before I did (1997) and moved to be with his parents in Nevada. Nice guy.