one cooling fan running when ignition on although cold engine

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mac2
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Joined: Wed May 11, 2016 10:24
Model: Excel SE
Colour: MediterraneanBlu
Year: 1988
Location: East Yorkshire

one cooling fan running when ignition on although cold engine

Post by mac2 »

I recently replaced the nearside radiator fan as it wasn't working. When wired up correctly it runs the moment the ignition key is turned to the first position even though the engine is stone cold. The offside fan does not come on until the engine reaches the temperature to require it.
Clearly the nearside fan is receiving current inappropriately. I have checked the wiring for any 'modifications/bodges' and can find none.
Looking at the wiring diagram there is a relay which is a double make/break, thinking it was possible that one of the circuits could be permanently 'live' I checked the continuity. From the diagram in the service manual with the relay on the bench my understanding is that there should be no continuity between terminal 30 and either of the two 87 terminals. To my initial joy I found there was continuity between 30 and one of the 87 terminals 87a to be precise. Thinking that the relay was faulty I aquirted another relay and to my surprise it was the same ... continuity between 30 and 87a. Maybe both relays have the same fault. Before aquiring a third relay I wondered if there is a flaw in my understanding of the relay circuitry and if anyone has a spare relay which they know to be functional are the results the same as i have described. If not then clearly I have two relays with the same fault despite the odds against.
Many thanks to anyone who offers a reply.

Pete Boole
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Re: one cooling fan running when ignition on although cold engine

Post by Pete Boole »

It sounds like you've got a change-over type relay there. Relays with terminals 87 and 87a are this type. Do you need a dual contact/double output type - with terminals 87 and 87b?

Pete

mac2
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Posts: 20
Joined: Wed May 11, 2016 10:24
Model: Excel SE
Colour: MediterraneanBlu
Year: 1988
Location: East Yorkshire

Re: one cooling fan running when ignition on although cold engine

Post by mac2 »

Many thanks Pete. It would appear that the diagram in the service manual is such a double output relay but the two I have with the 87a terminal are as you say changeover relays. Which work perfectly but are wrong type.
Looks like you have solved my problem. Once again many thanks

Pete Boole
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Joined: Tue Apr 04, 2006 21:28
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Re: one cooling fan running when ignition on although cold engine

Post by Pete Boole »

You're welcome. At least you know they work! :D

Pete

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DavidOliver
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Re: one cooling fan running when ignition on although cold engine

Post by DavidOliver »

Hi Mac2. The Section MF electrical manual on page 35 shows the three different Relay types.
I am not sure you have solved your problem, I understand the second fan comes on when the A/C is switched on and the engine is at temperature.
I assume it worked correctly before. I suggest you check the number of pins the relays holders have.
Ther are several relay ways you can get the required sequence of each fan to work.

Dave the cog.

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