Rad fan help

Howdy folks, I'm having trouble with the cooling system on the cabby it doesn't seem to be working. I've checked fuse 1 and it's ok . I bridged the connector to the thermo switch and the fan runs . I've checked the switch itself with multimeter and it seems ok also had a spare which seemed ok both are or switches . Also changed the coolant temp sensor . Seen relay 53 runs rad? Seemed to be new . One concern I have is the wiring to the fan there's three pins on rad fan but only two wires to the fan? 

Year and Model help, also if your car has A/C or not?

On early cars the fan was 1 speed so only had 1 connector. Later fans were 2 speed and had 3 terminals. Common solution to just use 2 terminals when using a lter motor on an early car so nothing wrong with that.
If you have tested the thermo switch by seeing if it is closed when in some boliing water then it is fine. There should be a temp stamped on the side of it which is when it should close.
How do you know the system is not working as it should?

Sorry Briano, 1990 dx engine changed to aaz diesel  no air con. Paceman 95 d.g I seen stamped on both switches  both of which were Vw switches . Needle keeps rising over half way  flashing light comes on . I haven't heard fan come on . I don't want drive the car and boil the engine . Radiator is new and coolant  has just been flushed recently . Coolant reservoir is trickling away thru the small hose so assume thermostat is working correctly. Thanks lads 

is it over heating? does it boil up?

the fan usually only comes on when its a hot day and you are doing a 7 point turn

EDIT: but I would expect it come on before the flashing LED, note the LED is also for low coolant level

Not overheating cos I haven't let it the led came on and I turned off engine. Needle was over halfway up by then . Maybe I'm being paranoid and not letting it kick in , but led came on so wasn't risking it . Incidentally I cakes the circuit in the clocks and they looked good 

gafo said

Not overheating cos I haven't let it the led came on and I turned off engine. Needle was over halfway up by then . Maybe I'm being paranoid and not letting it kick in , but led came on so wasn't risking it . Incidentally I cakes the circuit in the clocks and they looked good 

needle runs ok at more than half way on both mine, 1.8 GTI and 1.8 Carb

theres a few posts were people do get scared and swap thermostat and radiator and fan when it was working just fine

get one of the cheapey lazer temp sensor guns things and see what temp the rad and expansion bottle are getting to?

Cheers mate, I thought that might be me next step I'll  get my hands on one and try that next.. I thought I'd be driving this by now one step forward two steps back 🤷🏿‍♂️Thank again folks👍🏻

Is the radiator getting hot?
As has been said, they do run with the needle quite high. If the radiator is getting hot then the thermostat is working and the system doing what it should.
One thing could be the temp sender reading high.
The other one, is related to the lamp itself - depending on the year of your car, there could be a coolant level sender (in the expansion tank), these can corode and give eroneous readings causing the lamp to flash. The circuit in the temp guage itself can go bad and cause erroneous flashing.

You can get temp switches that run close at lower temps. https://www.classic-vw.co.uk/sensors-senders--switches-1950-c.asp

From the most helpful Briano1234  Worth a read https://www.volkswagenownersclub.com/threads/repairing-your-flaky-water-temp-gauge.32211/

Thanks mate ,The thermo switch I have is listed on that link u sent   . Different part number though. Part number on my switch is  321 959 481E . 95 degrees stamped on it. Seen the lower d g one too.  I have one of those temp reader sourced just have to pick it up. So I'll test it on car when I get it. Thanks again 👍🏻

gafo said

Sorry Briano, 1990 dx engine changed to aaz diesel  no air con.

No worries, I like to know the year and engine type.

Well in 1990 most Golfs/Cabby's has a coolant level sensor that was in the middle of the expansion tank.

This sensor is a 28mm Black plastic thing that has 2 metal probes at the ends.  These ends get corroded, and will act the posterior flashy light in dash.

The coolant level sensor only works well with a 50/50 blend of AF to Water.  These Probe ends get calcified and the resistance of them change.  Clean them up shiny.

There were also some after market expansion jugs that didn't have a bleed hole at the top of the senders cylinder.  So when your levels dropped it would form a
Air pocket, that left the probe tips with no coolant around them. Flashy light in dash usually when doing a hard turn.

Using a 2 speed fan in a non-a/c car is fine.

I don't like seeing that much corrosion on connector or pins on the radiator fan, clean them.

T-stats should be matched to the Radiator Fan switch.
so using a 95 temp fan switch would also use a 95 temp t-stat.

Grounds on these guys is always a issue.

The Early 1980 Diesels had the most simplest Radiator Fan Circuit.  Batter to Radiator Fan Switch, then From the Fan switch to the Fan.  The Fan has a separate ground wire as it is Isolated to the Frame because of the plastic tanks, and mounts.  So be Sure that your ground is good to the fan.

The 90's Cabbies that I drove's fan would usually come on if I was running down the road for a while then pulled off and stopped so the Gauge would heat spike the fan would kick on as there was no air flow over the radiator/engine.  Even testing them in the garage it would take a good while for it to turn on and cycle.

My 80 diesel would cycle the Fan on a hot day, as the temps on the parking lot at work were over 120 degrees F.  This is with the car not running for a couple of hours, and parked.  The first few times it was un-nerving.  Till I got a Haynes and Poured over the Schematics.

I don't have a lot of hands on with a AAZ as I was rocking the 1.5 Diesel for over 20 years, but I do have a lot of time with the 90's Cabriolets with a/c and 1.82h.

As you had a engine swap I don't know if yours has the 53 relay next to the Battery on a Bracket on the inner fender, as that is used to power the after run fan circuit.
Those 53 relays were subject to water ingress causing corrosion, rust, and flaky operation.

On a 90s 2h digi the after fan run sender was a single pin Brass nut looking thing that was attached to the rear side of the Valve cover.

The 90's cabbies had 2 main relays one in the fuse panel and one of the fender, a after run fan circuit, and the coolant level sensor.
Radiator Cards are a must for proper operation.

If you decide to replace a radiator switch get one that matches your t-stat, then test it in water with a thermometer to validate that it switches on at the right temp.  You can also test your current one this way.

Here is a write up I did for Fan operation in a 90 Cabby with a/c.

https://www.volkswagenownersclub.com/threads/radiator-fan-operation-explained.54346/?id=54346










 

Wow , some reply Briano thanks, yes it has the coolant Level sensor  on the exp tank. 53 relay is inside with fuse box. Never noticed any fan to body earths . I'll check the  sensor in the exp tank. Thanks again 

Back again , I borrowed a laser temp reader and ran the car on the driveway the temp light start flashing after needl passed halfway and tit was up to 130 dg and fan hadn't kicked in . Just checking should I have voltage at the thermostat switch with the ignition on? 

130c? even with antifreeze and under pressure (raising boiling temperature) it would have boiled up at 130c.

Also by that time the guage would be well into the red section.

my understanding is the the thermoswitch is live all the time, hence the warnings about keeping fingers out of the way when working under the bonnet even when ign off

EDIT if you connect together the 2 wires going to the thermoswitch, does the fan run? It should do.

FIrst thing I have found is that Gauges are always suspect.  I have owned 4 cabbies, and all of them suffered from mal-functioning gauges.

I set out to find out the culprit and of the 6 gauges I had taken apart all 6 were fixed with a soldering iron and new solder.

Here is the like to my repair. It isn't for the faint of heart as the Clocks have to be disassembled. GREAT Care should be taken with the Mylar.

1,
https://www.volkswagenownersclub.com/threads/testing-digifant-water-gauge.32195/

2.
https://www.volkswagenownersclub.com/threads/repairing-your-flaky-water-temp-gauge.32211/

In 90's USA versions, and I thought most else wheres.
They did a few things different in the original GOlfs and Rabbit of the 70's and early 80's.  The Radiator fan was
Very simple.

Original
Battery-to-fuse-to-radiator-fan switch Left side through switch to Motor.

With the Advent of AC
You have to look at the Back of the Bentley for the ones with a/c to see how they are Gaggled together, it works but it can be confusing.  They used a 3 pin switch, and a relay to engage the fan at all times the a/c slider is in one of the a/c positions (high speed).

In the 90's that I am used to They added a After run Thermoswitch and a separate relay to the mix.  The Relay is in front of the battery, and it turns on the Fan to cool the engine after running for up to 15 minutes. Then can switch on at any time.

With the installation of the Diesel engine in the car, you hope and pray that they didn't screw too much with the wiring and got it right.  

I would start with locating a new Radiator fan Switch 2 pin or 3 as you do have a 2speed fan.  Test it to make sure that it picks when hot.  (I used to boil them with a thermometer and my DVOM.  Now I use a DVOM with my DVOM set to continuity for the beep.  I then use a Cigarette lighter to heat the brass bit and let it buzz.  Once it trips I leave the DVOM connected to make sure that the thing opens the circuit when cool.

I would also suspect my Gauge, which is why I test them with a battery fro the sender to the Gauge as they are same but different circuits.  

The Gauge doesn't control the fan.  It is an indicator that something is amiss,  if it is running low on the scale then I suspect cold solder joints in the unit.

Also the heat of your radiator isn't a good judge of the engine temp, you have to hit the engine and the coolant flanges to get a average.  Also if your upper radiator hose is hot but the lower isn't then you have issues with the system and possibly a t-stat issue or a failed Water pump.  Test all t-stats prior to putting them in.  I use boiling water to make sure they (pop) open fully, as a partially open t-stat is the same as one that won't open.

Here is my take on how it works.
Radiator Circuits explained? - Topless Rabbit Forums

Back again , I had a hour today at the cabby I was checking the wiring to the thermo switch and I pulled connections apart and they where badly corroded so I cleaned them and thought that was the issue but that be too easy. Now I have 12v to the switch but fan didn't come on when I got it up to temperature. I even swapped out the thermo switch for another one I had .no joy. Fan works when I bridge the terminals to the switch🤷🏿‍♂️

It appears down stream from the thermoswitch works OK if the fan spins when jumping the wires at the switch.

Unlucky if you have 2 duff switches. Does it actual boil up? What are you classing as 'up to temperature'?

I have come across a problem on a 1300 MK1 were it appears the thermoswitch is screwed into the side of the rad straight into the water….. there are small galleries in the rad and those around the switch were clogged with debris/sludge and not allowing it to reach the same temp as the water in the rad

Have you tested the switches in boiling water?

How u doing ? I have it running on the drive the needle gets up beyond half and onto the mark beyong the led light then I turn engine off. The laser temp reader is showing about 110 to 130 on the thermo switch . Lower rad hose is 95 to 110 top hose is hotter . Rad is new and I flushed the system before I filled up with coolant and water . Rad turns on when I bridge the terminal s