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Rad fan issue - EMS signal to Relay Module? 2 months 3 days ago #205773

Hi all!
The rad fan on my MGF 1997 (with AC) does regretfully not run. Have read a lot of threads, and with aid from these the following has been checked and done:
Fan(s) runs when 12V applied directly.
Brown plug on temp sensor removed (nothing happens while ignition on).
12V and Ground measured ok at the Relay module.
Fan relay inside the Relay module reacts when given 12V directly (and of course the fan runs then).
No signal measured on the "UY" from ECM to the Relay module, when ignition on.

Has anyone experienced that the ECM is "dead" on this issue only? Or are we missing something here?
Appreciate any input, this is more or less the last headache on the car before the MOT - for the time being :-)
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Last edit: Post by Cobber.

Rad fan issue - EMS signal to Relay Module? 2 months 3 days ago #205774

Have you checked the circuit diagram to see if there is another fuse in this circuit that is not immediately obvious. Different fan at the opposite end of the car but I experienced something similar on the engine fan. Once someone had pointed out there was a 2nd fuse I was able to find why that fuse was blowing. In my case a low resistance fault in the fan motor that allowed it to run for a short while but then blew the fuse
2003 TF 135 sunstorm

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Rad fan issue - EMS signal to Relay Module? 2 months 3 days ago #205776

Thank you for the feedback - we believe to have checked more or less all the fuses (measured). Passenger compartment and in front. Also cannot see in the diagram to be a thing we have forgotten, but...

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Rad fan issue - EMS signal to Relay Module? 2 months 3 days ago #205777

Just a thought but does it use a straight negative feed from ground or is a switched negative provided from the SCU ?
2003 TF 135 sunstorm
The following user(s) said Thank You: runeme

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Rad fan issue - EMS signal to Relay Module? 2 months 3 days ago #205780

Do two switched negatives become a positive?
An existential question in both semantics & mathematics.
M

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Rad fan issue - EMS signal to Relay Module? 2 months 3 days ago #205783

Hi, the fan does not have a straight ground feed, it all goes through the relay box. The common ground point close to the battery have been throughly cleaned and checked however...

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Rad fan issue - EMS signal to Relay Module? 2 months 3 days ago #205784

doubble post - sorry

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Last edit: Post by runeme.

Rad fan issue - EMS signal to Relay Module? 2 months 2 days ago #205790

Do two switched negatives become a positive?
An existential question in both semantics & mathematics.
M

It's a long time since I was at school but IIRC adding two negatives together is a positive but multiplying them together is a negative. :-?

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Rad fan issue - EMS signal to Relay Module? 2 months 2 days ago #205792

What happens when you give the fan a direct negative feed ?
2003 TF 135 sunstorm

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Rad fan issue - EMS signal to Relay Module? 2 months 2 days ago #205795

The relay does not engadge, so it will not help to give direct earth to the fan as far as I understand.
BUT, we might have misread the wiring diagram and measured the "blue/yellow cable" (from ECU) into the relay box against earth/ground. I now may rethink - that the blue/yellow cable might give "earth" from the ECU to the relay control. If that is the case, we have to look at the + side of the control signal to the relay...

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Rad fan issue - EMS signal to Relay Module? 2 months 2 days ago #205796

I’m positive that you are correct in what you say, but multiplying two negative numbers together produces a result of much lower value than the initial number.
When one multiplies one produces more, to get less, surely you have to divide.
Semantics or mathematics?
M

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Rad fan issue - EMS signal to Relay Module? 2 months 2 days ago #205797

I’m sorry Runeme for sliding this bit of “nonsense” into your post, if you becomes a regular visitor, which would be nice, you will have to get used to these deviations.
It can get wonderfully daft when Cobber gets fired up (I was going to say “let’s rip” but that would create problems).
M
The following user(s) said Thank You: Notanumber, runeme

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