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Discussion Starter #1
I am trying to test my way through the wiring on my 164 recently undergone a rebuild, the cooling fan doeas not operate and I have come to a crossroad with it , I can,t identify where the grounding point for G53b is , everything at the moment points to this, Iam at Test A13 on the cardisc, sorry its the only way I can do leccy work.:confused:
 

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I am trying to test my way through the wiring on my 164 recently undergone a rebuild, the cooling fan doeas not operate and I have come to a crossroad with it , I can,t identify where the grounding point for G53b is , everything at the moment points to this, Iam at Test A13 on the cardisc, sorry its the only way I can do leccy work.:confused:
Hi Alfapat

Whick fan (cabin or rad)?

Have you checked that the fuse strip is ok? (rad fan fuse is situated on the passenger side, on the front of the false firewall - inside the block where the main starter cables are attached).

;)
 

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I am trying to test my way through the wiring on my 164 recently undergone a rebuild, the cooling fan doeas not operate and I have come to a crossroad with it , I can,t identify where the grounding point for G53b is , everything at the moment points to this, Iam at Test A13 on the cardisc, sorry its the only way I can do leccy work.:confused:
Alfapat

There is a 40amp fuse that is the main supply for the fans on a 24v car this is located in the engine bay righthand side on the bulkhead next to the brake cylinder, mine corroded away on the fuse about three years ago and it took Alfa romeo about 2 months to source a new one for me. Once I replaced this fuse every thing came back on line. From the fuse from memory the cable went to the two relays on the front bulkhead these relays are controlled by the 2 stage sensor down on the bottom of the radiator left hand side as you look at the engine bay.
I hope this is some help to you

Mick
 

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Discussion Starter #5 (Edited)
No fuse is fine , I have past that check, gone a bit further on now but have not found G53b ground yet, its possibly the thermostatic switch but not sure untill I boil it in 100 degrees, then I should get a resistance reading don,t I ? Its open circuit at the moment.Only thing its a coincidence that both feeds are not getting through ithe switch in its normal situation.
 

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No fuse is fine , I have past that check, gone a bit further on now but have found G53b ground yet, its possibly the thermostatic switch but not sure untill I boil it in 100 degrees, then I should get a resistance reading don,t I ? Its open circuit at the moment.Only thing its a coincidence that both feeds are not getting through ithe switch in its normal situation.
Alfapat

I believe there is a common wire one of the three wires to the Rad sensor, when cold all should be open circuit off the common wire, when it reaches first temp it should make on one of the 2 wires and you will hear a relay click in on by the near side by the rad and this will bring on low speed fan, when it gets to the higher temp the 2nd speed on the fans should come in on the 3rd wire via the 2nd relay which you will hear click in next to the first speed relay.

Mick
 

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I would have thought that the easiest way to check for a good earth is to measure the resistance between the common (earth) pin of the two-stage thermal switch and a convenient earth point (such as the engine), rather than trying to play "hunt the ground". You should be able to see 12V at the other two pins with the engine cold. If you get 12V at these two pins and a low resistance at the common pin (<0.5 ohm), then suspect the thermal switch.

If you get a high resistance between the earth pin and the vehicle earth, that's the time to check that it's grounded properly at G53b.
 

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Discussion Starter #9
Thats great lads, when I loop the plug connecting the thermo switch the relay certainly clicks, as does the other speed wire but no fan comes on.So what your saying about the resistance on the black wire should be under 5 ohm with ignition on,and for the 12v and measure between one feed and black the reading should be under 5, is that correct?
I will be back ,in middle of sorting the misses Audi after MOT fail both back brakes discs and rear coils, tough job in this heat!
 

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Thats great lads, when I loop the plug connecting the thermo switch the relay certainly clicks, as does the other speed wire but no fan comes on.So what your saying about the resistance on the black wire should be under 5 ohm with ignition on,and for the 12v and measure between one feed and black the reading should be under 5, is that correct?
I will be back ,in middle of sorting the misses Audi after MOT fail both back brakes discs and rear coils, tough job in this heat!
Alfapat

If the relays are clicking and the 40Amp fuse is ok the fans should run, check the connections on the fans there may be corrosion therefore not allowing voltage to flow due to high resistance put your volt meter on the terminals of the fans once you have linked out the plug to the thermo switch and see if you have voltage at the terminals of the fans.

Mick
 

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Discussion Starter #11 (Edited)
Ok ign on, therm switch joint plug disconnected and looped black to whatever speed, measured voltage accross red and brown coming out of plug and voltage is 12v or there abouts as battery on a stress mode at the moment!
Resistance is 0.5 accross both terminals, but no fan on.
Measuring black from therm sw, with ign on ; ie blk to earth resistance is 0.3 ohms

Boiled spare therm switch and both speeds measured to blk resistance appears anything from .023 t0 .045 on boiling point , so we know that works . Will drain coolant and remove therm sw tomorrow and test that.
God this is a pain!
 

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Basically, with the engine cold and the ignition set to run, you should get 12V at each of the pins circled in red. You should get a low resistance between the pin circled in green and the vehicle earth. If you get all of these, then its likely to be the thermal switch. As Mick said, if you're getting the relays clicking when looping across the thermal switch pins, and the fuse is intact, then that would tend to also point to the thermal switch.

 

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Discussion Starter #13
Yes Iam getting the values you mentioned, however can you tell me if both ends of the 40amp should be 12v on ign on or does that only happen when the fan is supposed to kick in, I get the feeling that my wiring in is wrong at the fuse,I can,t think why.
I have replaced the thermal switch for one that shows aresistance but my figures may not be high enough to trip the connection?
I have run car again to no luck it only boiled again at 90 degrees so the cold sensor or high temp sensor is 10 degrees out, I presume there is no direct link?
 

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I am trying to test my way through the wiring on my 164 recently undergone a rebuild, the cooling fan doeas not operate and I have come to a crossroad with it , I can,t identify where the grounding point for G53b is , everything at the moment points to this, Iam at Test A13 on the cardisc, sorry its the only way I can do leccy work.:confused:
g53b is ground location on left front of engine bay,. sort of under the left headlamp.

Check all connections on false fire wall. Make sure they are tight.

Confirm 12V to fan motor. Confirm 12V to fan switch. Did you try to hot wire the fan motor alone?

Did you bypass the resistor? If so return it back to stock.

Confirm the fan motor works with direct current to it.

Jason
 

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Discussion Starter #15
I do get 12v at the fan but does not kick it into action once I put the plug back in?
I have hot wired the fan also from a battery and it works fine, I have hot wired the relay junction at pin 87 and 30 and the strange thing is when I loop the thermo switchthe 12v dissappears when connected you hear the coorresponding relay click and measure the bare loop and no voltage, the same thing occurs when I loop pins 87 and 30 , pin 87 having 12v? This is why I must seek out g53b I will check this ground tonight when I get home.
 

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Yes Iam getting the values you mentioned, however can you tell me if both ends of the 40amp should be 12v on ign on or does that only happen when the fan is supposed to kick in, I get the feeling that my wiring in is wrong at the fuse,I can,t think why.
I have replaced the thermal switch for one that shows aresistance but my figures may not be high enough to trip the connection?
I have run car again to no luck it only boiled again at 90 degrees so the cold sensor or high temp sensor is 10 degrees out, I presume there is no direct link?
Yes, there will be 12V at the fuse when the ignition in switched on. It's the relays that actually switch current to the fan, either directly, or through the resistor, according to fan speed.

I wouldn't expect the temperature gauge to be particularly accurate. Besides, it's only measuring a spot temperature at one point in the engine.
 

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Faulty fan

hi PAT
have spare fan,if all else fails, which you can have for £15 including postege
YOUNG ALF
01727858472
 

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Discussion Starter #18 (Edited)
Yes but it works from an outside power, thanks for offer, I have one on a scrapper anyway,and since I know this one works, its not in the wiring environment its supposed to.
Just had another shot at it, renewed ground 53b and all is well there now, interesting point is that there is 12v at pin 87 on relay but not when you loop the thermo switch, it disappears, also with switch looped12v appears at fan plug, connect to motor and nothing ! The current is going somewhere but you would think the fan is at fault, checked the firewall fuseand its ok, checked the cooling fan fuse also, I am going round in circles!:rolleyes:

There is more Ok, I have exhausted the checks that I can do, and going round in circles, I get the feeling that I need to trace the path of the brown wires, thought that was the earth point but no, I will follow the loom back to the firewall as it seems that these wires are reponsible for the lack of current, as in power not volts. When you get 12v at the plug when looping the switch and plug it in the fan nothing happens so the power is losing itself somewhere, as the relay has 12v as well at the brown wire , this disappears as well?
Anyone have an idea where these wires end up , then I can do a continuity check.
 

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I do get 12v at the fan but does not kick it into action once I put the plug back in?
I have hot wired the fan also from a battery and it works fine, I have hot wired the relay junction at pin 87 and 30 and the strange thing is when I loop the thermo switchthe 12v dissappears when connected you hear the coorresponding relay click and measure the bare loop and no voltage, the same thing occurs when I loop pins 87 and 30 , pin 87 having 12v? This is why I must seek out g53b I will check this ground tonight when I get home.
Relay!!! I am thinking relay here. G53b is right there next to the front left chassis under the air box.

Did you pull the relay and loop 87 to 30?

or did you do it from underneath the relay?
 

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...interesting point is that there is 12v at pin 87 on relay but not when you loop the thermo switch, it disappears, also with switch looped12v appears at fan plug, connect to motor and nothing !
Totally as expected as you have effectively connected that point to earth. A voltage will only appear across a resistance (open-circuit essentially being an infinite resistance), due to what's called potential difference. When you loop the thermo plug, you are creating a short-circuit to ground - i.e. no resistance. Therefore I would expect to see 0V at pins 87 and 30 of the relay and pin B of the fan motor, with the fan connected, as they are at the same potential as vehicle earth.

You should still see 12V at pin A of the fan motor as the motor coil has a resistance which will produce a voltage across it when current flows through it, according to Ohm's Law - Voltage = Current x Resistance. If you don't, then it might suggest a short in the fan motor coil but this is unlikely as the fuse would probably have popped.
 
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