exploring my engine bay and getting familiar, i found a sensor(2 wire) that i cant find in the repair manual. if you are facing the engine from the front of the car it is located just below the rear left valve cover corner. it is attached to a bracket. it doesnt plug into anything, its just attached to the bracket. anybody know what this sensor is? **also my temp gauge does not work in the instrument panel and i was trying to locate the sender for that gauge. i cant find it.
i thought it was part of the large sender (4 pin multi function sender) below the coolant outlet. i have conflicting views where the water temp sender for the gauge is. anybody know for sure?
emanuel
87 5000s

It has a large rubber boot covering it directly on the bottom of where the top radiator hose connects to the head. Some of these switches have only 3 pins (the forth was the 12v power) but the newer models don't need it anymore. I think the MC engines have it.
I'm also wondering.. not too sure though... theres a one wire sender on the very top of coolant outlet. I had it replaced believeing it had something to do with my temp gauge, but it didnt help me. (it was cheap)
Anyway, that mulit function switch is whats supposed to control your gauge (especially if it works speratically). Well, so says my Bentley.

i know about the 4 pin switch. the haynes manual
says the coolent temp sensor is at the rear of the cylinder head. go figure. f*$%#&n haynes!
if the 4 pin sensor controls the temp gauge, then
if my temp gauge doesnt work i'm assuming that the 4 pin sensor is bad. correct?

no turbo here. still got that sensor though.
has a part # 034919369A
85-80 130c max

its just screwed into a bracket on the left rear of the valve cover. ambient temp sensor? :)

no turbo here. but i still have that sensor.
part # on it says 034919369A
85-80 130c max
2 wire
ambient air temp sensor? :)
its not screwed into anything except the bracket.

It's located just below where the upper rad. hose goes into the block. The plug in connector is supposed to be protected by the rubber boot surrounding it, but usually just serves as place for errant coolant to gather.

If you replace it with a four pin or a new three pin unit, the gauge will start working again if there aren't any other problems with the wiring. On some cars I've seen, the connector like to crumble into nothingness since the plastic connector has been heat soaked so many times.

I don't like buying new ones, so I go to the junkyard (my home away from home) and pull the multifunction switches out of newer cars, or look for the shiny brass on older cars, indicating its a new part. Then look on the side, most of them have a date code engraved or stamped on the side. If it's original, it's probably toast...

Best of luck.

-Steve Jensen
(not suffering from writer's block this evening)
2 mistresses with four rings

thanks steve. i was going to ask if i can use the newer 3 pin sensor instead of the 4 pin. if you lived up this way i'm sure we would know each other. the junkyard (pick a part) is my second home as well. i picked up 4 sensors the other day, one of them has to work, all of them were the big sensors covered by the coolant trapping boot. junkyard man charged me a buck apiece.
also picked up other sensors, gaskets for the ps
cap, a bomb(looks recently replaced), and other
asst goodies. got a side audi emblem from a wrecked audi and turned it into a keychain. i love my dremel!

The bracket is show attaching to the valve cover about 2 bolts from the rear on the driver's side. Does this sound right?

The Multi-function Temperature sensor is mounted underneath the coolant outlet on the cylinder head. It uses a 4 terminal connector which is normally is covered with a protective rubber boot.

The newer style replacement Sensors will have only 3 terminals as they simplified the internal design of this sensor and eliminated the +12V supply to this sensor.

There is a fuse which supplies +12V to this sending unit, fuse #12 should be checked if you have trouble with the temp gauge operation or you suspect a problem with the Multi-Function Temp sending unit.

its on the passenger side. rear corner of the valve cover. my guess is that it senses air temp/ heat from the engine.

steve,
i used one of the $1 sensors that i got from the junkyard. it was a three pin(newer style). i just removed the old one and screwed in the new one.
plugged in the connector and now my temp gauge works. i love junkyards. this weekends special is
alternators and starters for $5. think i'll pick up one of each. :-)

BINGO,
i shut the car off and waited for the after run fan to turn on after a spirited drive. then i disconnected the terminal on the sensor and the fan turned off. this sensor must have been bad because if was drawing 12amps while the fan was running for about 15 minutes(seemed to be a long time to me). drew my battery down to almost nothing. i kept needing a jump so i bought a new battery, replaced the sensor and all is ok.