stylingpat

Hello everyone!

I'm working on a friends 91 w124 300te m103.98

I've got a few quick questions that I can't seem to find answers too.

How do I test my 2 aux fans up front?

Standing at the front of the car looking at the engine, when I turn the car on, the left one kicks on high speed right away while the right one doesn't.

Same thing happens when I turn the AC on. The left one turns on and the right doesn't. I checked the fuses (never seen fuses like this and couldn't find a picture of a blown one. But I read it would be extremely obvious if one was blown. I know what a blown fuse looks like. So these look good, unless I have to remove the fuse to see if it's blown. Also do I have to disconnect the battery to touch these fuses? Seems so since they are exposed and not in glass or plastic.

Moving on. How do I test these round pin relays with a multimeter? I've searched and couldn't even find any info on them.

How else do I check these aux fans especially since the one isn't kicking on.

Photos would be great. I've been having a hard time finding location photos of items in the engine bay. Even with a Haynes manual this has been patience testing compared to working on other vehicles.

I'm at idle right now and with a contact temp gun I am reading
105*c on the exhaust side of block next to freeze plugs.
99*c thermostat housing
95*c top of engine next to oil cap
90*c lower rad hose
95*c upper rad hose

This is with AC on, new hella thermostat and radiator with new Zerex g-05. I don't know if I can attach pictures on this forum. My dash board coolant gauge is reading on the line between 80 and 120. When I drive it drops down near 80.

Also should car run hotter or cooler with AC on? What are the standard operations of the 2 front aux fans.

Thanks a bunch!

Plutoe

Dear befuddled---the reason for you befuddlement is that you do not understand the function and control of the two stage aux fan.

The stage 1 and 2 on\off action is contrilled by relays K9 and K10 located in the fuse and relay box.

Stage 1 is when the refrig pressure exceeds 20 bar fan on and fan off at 15 bar

Stage 2 is when the temp sensor B117 senses a coolant temp of 107Cn + and off at a lesser value.

If you aux fan turns on withe lesser values you either have a faulty control module or the two sensors are faulty.

To confirm all this use a pulse counter and connect to pin 1 and 7 of the diagnostic connector and read the puses and then post the nimber of pulses-------

stylingpat

Awesome! Does anyone know where this plug goes? I just plugged this (red circle) together and it's blowing a fuse. It piggy backs off my driver headlight.

stylingpat

Alright so today the air conditioning system stopped blowing..

Where do we start. Give me the list to go through and I need pictures. I don't know where anything is in this engine bay. It's a m103.983 1991 300te.

I started by checking the fuses, none blown, and this guy. Unscrewed him and put him back on. Good.