cooling fan singular!!!

[CitroXim]

if i earth pin 1 on sensor plug (any good earth point) and then bridge pins 1+3 this should make the contact for the slow speed operation i think

its too dark to check now but will try and blow the car up tomorrow morning

colin

That's it Colin! Absolutely spot-on!

[admiral51]

thanks for the reassurance jim i knew if i walked away, had a couple of cans of the falling down juice i would get my head around it unlike the u bend on the toilet, never been able able to get my head around that one

colin

[admiral51]

quick update:
at the start i stupidly stated i had replaced relay for a known good one
it would appear this was a falsehood...untruth call it what you like well iwas told it was a good one
when i bridge pins 1+2 i get fast speed working..if i remove the fuse F3 i only get a click from the relay as it should
however when i bridge pins 1+3 i get nothing even with fuse F5 removed i get nothing from the relay
my assumption now is that the relay is faulty or bad wiring in the area of the relay (hope its the relay)
can anyone throw some light on which pins on the relay socket are which as in a top to bottom diagram as i may try and bridge these before i go hunting for another relay

will take my other xantia apart to get to the relays that i know work cos i can test them in their present location

cheers colin
thanks to Clogzz for the picture

[RichardW]

Colin,

I don't think it's the relay. If the wiring diag is correct in the BOL (ha ha!) then the relay only switches the earth between direct (high speed) and via the resistor (half speed) - even with the relay pulled and fuse F5 out you should still get slow speed by bridging pin 3 to earth (use a big wire - see my note below!). You need to check the continuity between pin 3 on the temp sensor and pin 3 on the resistor, and then between pin 2 on the resistor and pin 3 on the relay and / or pin 2 on the fan connector. If this checks out OK then the resistor is at fault, obviously if it doesn't then you have a wiring problem.

Interestingly the temp sensor is switching the full current on slow speed, so I would have my suspicions that that is kaput too. Check that it goes closed circuit pin 3-1 when you get to about 90°C or so - and then consider fitting a relay to handle this switching duty!

[CitroXim]

Colin.

I'm with Richard here...

For the record, the relay connections are as follows: (imagine a clock face, using the picture above)

9 and 3 o'clock are the relay coil connections. (85 and 86)

12 o'clock (30) is the common switching pole.

6 o'clock (87) is the normally open contact and the middle contact (87a) is the normally closed contact. When the coil is energised, 87 closes and 87a opens. This is known as a change-over contact set in old GPO telephone relay parlance....

So, with the coil de-energised, you will see continuitity between 30 and 87a but not continuity between 30 and 87. With the coil energised, you'll see exactly the opposite.

My slow speed relay socket on my Activa looks exactly like the picture above and every day I flick on the aircon to ensure the fans are still working. Glad I did today, I got stuck in the M1 roadworks between Luton and the M25 Junction and again at the QEII bridge The fans worked hard today. It was a good run though and nice to see the sea. My Activa used a scary amount of petrol though. Glad my employer was paying

[admiral51]

thanks Richard and Jim
looks like i will have to bite the bullet and get myself a tester as im sure ill go round in circles unless i do

on that note do you have any suggestions of a reasonably priced tester that is pretty much idiot proof (substitute as you see fit) with some paint by numbers destructions

colin

[CitroXim]

With regard to a tester Colin,

My preference, being on the wrong side of 48, is one with a moving hand. I believe what the young 'uns might describe as an analogue meter. I like these because you have a moving hand to show what is happening and you just need to glance at it, with these new-fangled digital jobs you have to look closely at a jumble of numbers to see what is going on and interpret. The only thing digital meters have going for them is high accuracy but this can also be their downfall.

I know that Maplin electronics do very economical analogue meters. Look for one with a few ohms ranges that will allow low resistances to be measured with a degree of accuracy and a DC voltage range that deflects the meter needle significantly when reading 12-14V. Some I have seen have a 10V range and then a 50V range and neither is much use for automotive work. A 25V range is nearly ideal.

Because digital meters can now be got for pennies, have one of each. One slight advantage of many digital meters is a continuity range that bleeps when you have continuity; this can be very useful for quick checks.

I have both, a cheap digital and a 40 odd year old AVO Meter Model 8. In fact I have three of them, all rescued from skips, sadly thrown away by hethans who believe there is no place in this modern world for the old corner-stones of electronic engineering such as represented by the old AVOs

[CitroXim]

...with some paint by numbers destructions

colin

If I'm teaching you to suck eggs here Coiln, tell me to shut up...

In electrical engineering, you are concerned with measuring three fundamental units. Current, Voltage and Resistance. The first was named after Ampere, the second after Volta and the third after Ohm, who formulated a law. Mr. Ohm stated that if you applied a voltage of one volt across a resistor of one ohm, a current of one amp would flow through the resistor. Mathematically, ohms law states that V (voltage) = I (current) x R (resistance). This formula can be rearranged in all the usual ways..

Car electrics are powered by a nominally 12V battery. Fully charged a 12V battery is actually nearer 13.8V and on full charge you will see a voltage approaching 14.4V across it.

A lot of items on a car consume a lot of power, starters for instance take hundreds of amps when cranking, glowplugs about 12 amps each, heated rear window about 20, another 20 for the blower on full tilt and roughly the same again for the cooling fan and so on. Because so much automotive electrical equipment has high curerent demands, it is clear from ohms law that very low resistance wiring and connections are required for these items to operate efficiently. If there is significant resistance in the wiring to the heated rear window for instance, the voltage available at the window itself will be significantly below 12v. For example, imagine there was a total resistance of 2 ohms beteen the battery and heated rear window and the window consumes 20A. Ohms law says there will be 4V dropped across this resistance, leaving only 8V for the window itself. Voltage drops across resistances alwas add up to the total, so in our example 4V across the resistance + 8V across the window = 12V. One point is that the engergy used in pushing a current thrrough a resistance is dissipated as heat and this heating often leads to more resistace and more heat until you have the fate that has befallen that relay base.

So, on to using the meter. Firstly, due to the currents involved and the need to measure current in series, pure current measurements are rarely carried out; instead voltage drops across resistances are measured and currents calculated.

The meter can be used to measure voltages across a suspect component and/or the voltage supply to a component. You can see if voltage is reaching a component by earthing the negative side of the meter to a known good earth. This will tell if the supply is intact but won't tell if the earth to the component is good. For this, you need to measure right across the component so you take its own earth into consideration. A low or absent voltage will then tell you the earth is bad. You can also measure voltage between a known good earth and a suspect one. If you see an appreciable number of volts, you know the earth is high resistance and therefore suspect.

The Ohms ranges read resistance. Zero ohms (usually full-scale deflection of the analogue meter needle) indicates a short ciruit whereas infinity ohm is an open-curcuit or a good insulator. Meters usually measure ohms in discreet ranges as the normal range of electronic component resistances go from tenths of ohms right up to 10 Megohms (10 million ohms) and beyond. Any resistance over a 1000 ohms and below 1,000,000 ohms is called a "K" (e.g. 10,000 ohms will be called 10K) and anything above a million is known as "Megs" This is far too big a range to accommodate on one test meter range.

As cars generally deal in low resistances and high currents, you need a meter that will measure these with some accuracy. If you say, read a 10 ohm resistor with a meter set to it's 10K or 100K range, it'll appear to read as a short circuit and may mislead, particularly if you're trying to find a bad earth. 15 ohms may represent a bad earth in a car but if your meter cannot accurately read low resistances like this, you may think that because the meter indicates what appears to be a short-circuit that all is well.

Resistace is always measured with all circuits dead. Never try to measure any resistance with anything live as the meter will object and (quite literally often) blow a fuse! This is because the meter powers the curcuit itself (usually from a 1.5V battery) to enable it to read resistance.

Analogue meters are also polarity-concious. If you have the probes the wrong way around, the meter will try to read backwards. Digital meters will append a "-" sign to the reading.

More advanced uses of test meters allow diodes and transistors to be tested but we'll leave that for part 2...

Hope that makes some sense Colin, If not ask away...

[admiral51]

hi Jim
a lot of what i thought i knew i realise now i didnt know
a lot i didnt know i needed to know i now know

it has been printed out and will be kept in a safe place for future reference

and on a lighter note.......................................................................

do you think i would have had better luck sorting my fan problem out if i had actually bridged the resistor plug pins as well as the rad sensor pins at the same time


i did manage to aquire 2 door straps from a scrappy today £3+vat a pair and what a nightmare to get them out and i got it all to look forward to again tomorrow

im off to find that corner with the big pointed hat in it marked with a capitol D and pretend today didnt really happen

colin

[CitroXim]

do you think i would have had better luck sorting my fan problem out if i had actually bridged the resistor plug pins as well as the rad sensor pins at the same time

Yes, that takes two things out of the equation at once. Link pins 1 and 3 on the sensor plug and short the resistor out (right across all three pins of the plug) and the fan should run fast.

im off to find that corner with the big pointed hat in it marked with a capitol D and pretend today didnt really happen

Get that hat off and out of that corner right now Colin! I had a very similar learning curve with hydraulics and felt like you many times, especially when reading posts by the acknowledged specialists in the subject like Mandrake It's what forums like this are all about, sharing the knowledge and learning

I'm glad you found the little tutorial valuable

A couple of things I should have added: Car electrical systems are always DC (Direct Current). The only Alternating Current (AC) like your house mains is inside the altrernator and that is converted (rectified) into DC before it leaves the alternator, so all voltage measurements are always made on the DC Voltage ranges of the meter.

You have to be careful when trying to measure the resistance of a suspected bad earth. Meters, be they digital or analogue, measure resistance using very little current and a bad earth might pass this and indicate a very low resistance whereas if that same connection is trying to pass 15 Amps it might exhibit a very high resistance. Basically, interpret what you are seeing and never take anything on face-value.

Another golden rule of electrical fault tracing is to keep it simple. Look for the simple things first rather than going all complicated at it

[CitroXim]

Colin,

This link gives the electrical diagram of the cooling arrangement.


http://www.eastment.net/forum/xantiawd.pdf

[admiral51]

thanks Jim gives me something to study

have put the fan problem on hold for a couple of days till i get my new tester and understand how to operate it now that i know what the results will mean

been up the scrappy again and got hold of a complete steering wheel and shroud plus a few door rubber strips and came away only £6 lighter than when i went in...seems he was impressed i had stripped the front doors/cards/speakers etc to get the door stays without trashing anything yesterday glad he didnt check my hidden stash of bits and bobs in my tool box relays screws bulbs etc

have removed busted stay from drivers door but cant seem to get the goodun back in convinced the window guide needs to out the way but will do battle again tomorrow

colin

[MikeT]

Hi Colin, if you and your patient are mobile and have time to spare, you're welcome to drop in - I've got a digital multimeter and two pairs of hands is often a godsend when testing wiring. It'll be like the blind leading the blind but you never know, we might get lucky

[admiral51]

hi Mike
thats a very kind offer and i will take you up on it but have just started a new job and hours are a bit hit and miss at the moment but i have your number
did try as you suggested but cant seem to find my messages on FCF at the moment may be a problem any ideas

colin