Cooling fans mystery
09-12-2011, 11:46 PM
#1
8th Gear
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Cooling fans mystery
Hi folks,
I'm a newbie here but have been on the Pelican Forums for a while. (I put a different version of this post there.) I'm currently troubleshooting several electrical issues bequeathed me by POs. Home-wired immobiliser installed ham-fistedly; other odd bits of home-wiring. These have caused no end of troubles. And fixing them is fussy and time-consuming. Sigh.
First on the current to-do list, though, is a cooling-fan issue.
On my 1986 NA (RHD, Euro-spec) both cooling-fans come on full when I turn on the ignition, and stay on all the time. They turn off again when I turn the ignition off. But all that work is presumably going to kill the fans eventually.
I followed the trouble-shooting procedure at Clarks Garage:
http://www.clarks-garage.com/shop-manual/cool-01.htm
The results are these: they confuse me a bit.
When I jumper the fan switch connector terminals 2 and 3 one fan (only) comes on full-bore (the left or passenger side RHD). When I jumper terminals 1 and 3 nothing happens.
With the connector unplugged and ignition turned on both fans come on full-bore as usual.
With the air-con relay removed both fans come on as usual.
It's not clear to me from this if the problem is the fan relay in the fuse-box or the thermo-fan switch. It also strikes me from the above that there could be another possible issue: the wiring to the thermo-fan connector. But I'm not expert enough to be sure, and the fan relay is too expensive an item to purchase in error.
Any advice appreciated.
One other thing. I have a spare fan switch, and was going to swap it and see, as a further trouble-shooting step. But for the life of me I can't get the old switch out of the radiator with the coolant drained and space created above. It seems firmly stuck (over-torqued?). But the radiator thread's plastic, I think, so brute force doesn't seem an option. Any suggestions?
Thanks in advance.
I'm a newbie here but have been on the Pelican Forums for a while. (I put a different version of this post there.) I'm currently troubleshooting several electrical issues bequeathed me by POs. Home-wired immobiliser installed ham-fistedly; other odd bits of home-wiring. These have caused no end of troubles. And fixing them is fussy and time-consuming. Sigh.
First on the current to-do list, though, is a cooling-fan issue.
On my 1986 NA (RHD, Euro-spec) both cooling-fans come on full when I turn on the ignition, and stay on all the time. They turn off again when I turn the ignition off. But all that work is presumably going to kill the fans eventually.
I followed the trouble-shooting procedure at Clarks Garage:
http://www.clarks-garage.com/shop-manual/cool-01.htm
The results are these: they confuse me a bit.
When I jumper the fan switch connector terminals 2 and 3 one fan (only) comes on full-bore (the left or passenger side RHD). When I jumper terminals 1 and 3 nothing happens.
With the connector unplugged and ignition turned on both fans come on full-bore as usual.
With the air-con relay removed both fans come on as usual.
It's not clear to me from this if the problem is the fan relay in the fuse-box or the thermo-fan switch. It also strikes me from the above that there could be another possible issue: the wiring to the thermo-fan connector. But I'm not expert enough to be sure, and the fan relay is too expensive an item to purchase in error.
Any advice appreciated.
One other thing. I have a spare fan switch, and was going to swap it and see, as a further trouble-shooting step. But for the life of me I can't get the old switch out of the radiator with the coolant drained and space created above. It seems firmly stuck (over-torqued?). But the radiator thread's plastic, I think, so brute force doesn't seem an option. Any suggestions?
Thanks in advance.
09-13-2011, 08:36 PM
#2
8th Gear
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Well, no suggestions so far...
However, going back through my forum searches again, I did happen upon a thread titled "bad cooling Fan Switch, a short circuit, or what????" from 2003, which does suggest other options for these same symptoms than the switch or $200 relay. Specifically the A/C, which can cause the fans to run all the time.
Unfortunately I can't seem to find a way to link it (advice on that?) , but a forum search will find it easy enough.
In case this helps others...
However, going back through my forum searches again, I did happen upon a thread titled "bad cooling Fan Switch, a short circuit, or what????" from 2003, which does suggest other options for these same symptoms than the switch or $200 relay. Specifically the A/C, which can cause the fans to run all the time.
Unfortunately I can't seem to find a way to link it (advice on that?) , but a forum search will find it easy enough.
In case this helps others...
09-13-2011, 08:51 PM
#3
Nordschleife Master
You might have a combination of problems.
The only time your fans should run at full speed is when the temp switch reached temperature or the AC is on. The AC will run one of the fans at full only, don't know which one on the RHD but it should run as soon as you turn the AC on.
With the car up to temp (hot) what happens when you turn the ignition off? You should still hear a fan running at 1/2 speed until the fan switch turns it off.
The only time your fans should run at full speed is when the temp switch reached temperature or the AC is on. The AC will run one of the fans at full only, don't know which one on the RHD but it should run as soon as you turn the AC on.
With the car up to temp (hot) what happens when you turn the ignition off? You should still hear a fan running at 1/2 speed until the fan switch turns it off.
09-13-2011, 09:05 PM
#4
8th Gear
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The fans turn off immediately with the ignition, and back on again with it turned on. They're responding to the ignition switch being 'on' only, not to whether or not the engine's on.
The link for the 2003 thread is here:
https://rennlist.com/forums/924-931-...t-or-what.html
That person spent hundreds for a shop to tell him in the end that it was the 'A/C receiver/dryer switch'. I'll read up on that in the factory workshop manual (Clarks Garage has nothing), troubleshoot the switch, and report back my findings for any poor schmuck who gets into my run-around.
The A/C answer does make some sense. I had an A/C issue develop at almost exactly the same time (give or take) as the fan problem, now that I think of it.
The link for the 2003 thread is here:
https://rennlist.com/forums/924-931-...t-or-what.html
That person spent hundreds for a shop to tell him in the end that it was the 'A/C receiver/dryer switch'. I'll read up on that in the factory workshop manual (Clarks Garage has nothing), troubleshoot the switch, and report back my findings for any poor schmuck who gets into my run-around.
The A/C answer does make some sense. I had an A/C issue develop at almost exactly the same time (give or take) as the fan problem, now that I think of it.