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Re: Which relay is doing that clicking?!?!?

Gerard wrote:


5. once at that temperature, turning the car off and restarting
           results in some furious switching noises from under the
           dash, doesn't always happen though and can sometimes
           happen at complete cold morning starts
        6. sometimes, after starting off after the car was as 100
           celcius, but having been left to cool off a bit, the
           clicking starts up when the 100 celcius temp is reached
        7. a few weeks back, when my knock sensor died and my intake
           temp sensor when bang, I drove home and pulled the codes,
           when the hood was open I noticed the radiator fan
           acting funny: on for a second, then off, then on, then off,
           and then just off. When the car is hot and I park it or when
           in traffic I can hear and feel the fan coming on at 100

I obviously suspect a faulty sensor in the cooling system or a stuffed
thermostat. The previous lighting faults could have been related to
a bad earthing point. What I'd like to know is:

        1. where are the major grounding points on the 1990 200t?
           Is there are grounding point at the radiator end of the
           engine bay? My secondary h2o pump does leak coolant all
           over the ABS pump and I am thinking it has done some
           injustice to electrical stuff below the pump.

        2. which relays under the dash are associated with the
           operation of the various parts of the cooling system?


I'd be willing to bet that the underdash clicking and the strange cooling
fan operation can be traced to the injector cooling fan thermoswitch 
and/or the after-run coolant pump circuit.  Look on the wastegate heat
shield just to the passenger's side of the cylinder head, towards the
firewall - you'll see a single sensor screwed into the heat shield.  It's got
one wire with a spade connector on it.  On my car, the spade connector
was loose and rattled off the switch - causing the furious clicking under
the dash as the wire flapped around, grounding the circuit all over the
place.   It could also be that the sensor itself has become flaky. 
Relatively cheap to fix.  

The after-run pump and the low speed on the cooling fan are triggered
simultaneously by the two-wire temperature sensor (two
rubber-shrouded spade terminals that extend horizontally toward the
rear of the car) where the upper radiator hose attaches to the cylinder
head.  If you short these wires together, the fan should run on low
speed and the coolant pump should run as well.  If not, the control
unit/relay may be history or the wiring may be suspect (many archived
posts about this relay going bad - Dave Head has talked about the fact
that it also functions as a pass-through for signals from the AC system).
This is a tall relay under the driver's dash, I don't know what the exact
location your car is.  

Best Wishes,