thermo time switch & water temp sensor wires?

[body_infinity]

RE: 1971 280se 3.5 v8 (w108) D-jetronic

Hi guys, just a quick question, I did notice the wires to the temp sensor (ts) and thermo time switch (tts) were slighlty off, the tts has a G and W terminal but the ts doesn't have any markings can anyone confirm the wire connections on these two?

I did see that the temp sensor wires have a blue with a white stripe and another wire that is a solid brown color, does it matter which wire goes where?

The TTS has two terminals which are round what color wire goes to the G and what wire goes to the W terminal?? if anyone knows or can make a quick check on their 280se v8 3.5 (1971 w108) engine that would be great...

thanks

[Jengasan]

Hello again...

Ok, the TS will have two wires - one 0.75mm square brown which is the ground and one 0.75mm square blue/white which should go to terminal 23 of the ECU. The actual sensor itself has two terminals and because it's only a thermistor it shouldn't matter which way round you connect the plug.

The TTS will have two terminals as you say G = 0.75mm Pink and W = 0.75mm Brown.

My terrible confession of today is that I couldn't be bothered to go to the car and take off the air cleaner to check first hand so the above I gleaned from the wiring diagram for our car if the colours don't match what you see let me know and I'll have the air cleaner off.

Hope that helps

Jengasan

[body_infinity]

thanks Jengasan, had a look at the thermo time switch (tts) but didn't see a brown wire only what looks like a light pink wire with a blue stripe and a solid pink (or is it brown)?? anyway when you get a chance to confirm that would be great


... also I decided to test the aux thermo fan (while ignition is on but engine not running) by grounding the single brown (with white stripe) from the aux fan switch/sensor and all I got was the fuel pump activate and a blown fuse (near where the battery tray is) there are two fuses (rated 16a) one was blown) tried again and the same thing..I am sure I read from another post that thats how you test it? anyway tried directly via a 12volt source and bang the fan works so kinda confused as to why the grounding of the wire from the aux fan switch would not work? checked the wire which goes to the alternator but all good??? any ideas /tips on this would be great ..

cheers again from B_I

[Jengasan]

B_I

First off...I'd recommend getting yourself the wiring diagram, its at the back of the official MB manual (check eBay) and probably on the CD the guys talk about on here. Much safer for test procedures than guess work as you could accidently melt a bit of the harness which is near impossible to trace or replace...which would be bad

I don't see why your wiring should be any different from the spec on the TTS, but I'll check Celia later and give you a shout on here, I'll havea thionk about the fan thing too. If some provious owner has been mucking about with the wiring its all the more reason to get yourself the diagram

Cheers

Jengasan

[Jengasan]

Hello

Now hopefully you're going to be too busy with your AAV surgery but here goes...

I'm a little confused myself by the TTS wiring as mine appears the same as yours ! (I should have known better than to trust a book). However, the cold start circuit on my car works perfectly well so I know the wiring is correct. On my car there is a fairly large square connector on top of the TTS which will only go on one way round...so is yours wired differently or what ? (photo opertunity?) Interestingly enough in the Main Wiring Harness section of the manual the connector is listed as having a pink and a pink/blue wire as we've seen...pity that contradicts the wiring diagram...go figure.

As for the fan........wasn't it working ? and do you actually have an overheat issue ? You live in Oz right...so go out for a good run and then park her up and leave the engine running the fan should cut in at 200(ish) F on the guage - if not then worry about it. Remember it's operated via a relay (which, if it doesn't work, is the 'usual suspect') so I wouldn't advise grounding out wires here and there.

I think Alabbasi is running an interestingly similar post on his 6.9 at the moment so you may pick up more tips there.

One piece of advice I'd give on these old Mercs....if it's not broke don't fix it...they were built pretty well to begin with. That doesn't apply to 35 year old rubber hoses though so go ahead and replace them

Hope that helps in some way

Jengasan

[body_infinity]

Hi mate...the tts switch on my car has no connector I did see the switch has a barb so I did assume it previously did have this but the connectors on the wires look new and I assume have been replaced but when I was cleaning the terminals I forgot which way the wires go... ......but I do have one solid pink wire and the other pink with blue stripe...dont want to just put them on and take a chance ;-)

I will try the fan test but have not seen it operate hence my test but will try again.. thanks Jengasan and hey if ur ever in OZ drop me aline owe u a drink or 2 or 3

cheers B-I

[Dbglobal]

I set up a bypass switch for my aux fan so I could turn the fan on manualy form inside the car. I wanted to be able to turn it on before it reached 212 degrees. Bypassing was easy.

[body_infinity]

Originally Posted by Dbglobal

I set up a bypass switch for my aux fan so I could turn the fan on manualy form inside the car. I wanted to be able to turn it on before it reached 212 degrees. Bypassing was easy.

Hi Dbglobal, that sounds like a good idea is it simply connecting up the fans wires via a toggle switch? will this also allow it to turn on when the air is on or even via the temp sensor?

Cheers

[Dbglobal]

Yes you can bypass the aux fan with a simple switch. The connector for the fan is near the left side of the radiator. Pull the connector apart and then just wire up leads via the battery for power. You can then turn on the fan anytime you want. One thing I did do was to get a switch with a led in it so I knew when the switch was on.

Regards,

Dbglobal