cooling Fan Staying On

[GaryF]

Driver's side cooling fan on the Sag is now staying on all the time when ignition is on.

Have tried changing relays but no joy. What's it likely to be? Dash ECU / thermostat / wiring? ...

Dash is reading correct coolant temp. Any help appreciated.

[ninetynine]

If you have air con probably trinity switch

[GaryF]

Do indeed have aircon.

Will consult Graham's Orange Bible to find where that is located. Any way to test for sure that it's at fault?

PS. Thanks for your help.

[shep1001]

If you swapped the relays and the fault did not swap fans then it's not that. If it was the temp sensor then both fans run by default - try unplugging it. If have the diagnostics software then plug the car in & see what temp the ecu is seeing as this is on a different sensor to that which shows the dash read out.

If it's the trinary switch try unplugging it, it's mounted in the top of the drier. think this starts the fan if the refrigerant pressure goes high. It's a right pain in the Arsenal to change as the system needs to be de/re gassed to do it.

[GaryF]

Thanks Shep. When I say I swapped relays it was just the fan relays to ensure that it wasn't a relay fault. The same driver side fan stayed on even with a different relay in place.

I did have a similar fault about about six weeks ago when the fan stayed on even after turning the ignition off completely and removing the key. Pulling the fan relay out and putting it back in 'fixed' it. I put a new relay in thinking it may be at fault.

Now the fan is on when the ignition is on. This just started to happen a couple of days ago. Also noted a battery voltage warning of 11.8 v which then rose to the normal 14.3 ish after 10 mins. Not sure if related. Will leave it in if not a straightforward diagnosis.

[shep1001]

GaryF said:

Thanks Shep. When I say I swapped relays it was just the fan relays to ensure that it wasn't a relay fault. The same driver side fan stayed on even with a different relay in place.

I did have a similar fault about about six weeks ago when the fan stayed on even after turning the ignition off completely and removing the key. Pulling the fan relay out and putting it back in 'fixed' it. I put a new relay in thinking it may be at fault.

Now the fan is on when the ignition is on. This just started to happen a couple of days ago. Also noted a battery voltage warning of 11.8 v which then rose to the normal 14.3 ish after 10 mins. Not sure if related. Will leave it in if not a straightforward diagnosis.

Diode pack on alternator on the way out? feel the alternator - is it warm when it should be cold. When my diode pack was on the way out the dash lights would stay on when the key was removed. They would switch off when you pressed the brake pedal!. Might be worth bunging in a new 100A fuse under the airbag at the same time just in case the fuse is fractured internally & on its way out. Could be earth issue too so check all the connections inc the battery and main earth off the alternator... the list can grow & grow until you isolate the fault but it does not seem terminal in anyway, just part of the joys of TVR ownership

Edited by shep1001 on Sunday 18th October 18:16

[GaryF]

Thanks again for more pointers Shep. I see from your profile that you are an electrician so it looks like I have the right set of ears! As you say, it's not sounding major.

I've had ten years now of fantastic ownership and a few minor niggles don't detract. Still love it!

[Little Mac]

I had the same problem in the Sag recently. Tracked down to a faulty relay and replaced. However, it still happens occasionally and I have learnt to simply tap the relay and the fan stops immediately. In my case, I think it is simply a dodgy connection but not sure this will necessarily help you here.

[shep1001]

GaryF said:

Thanks again for more pointers Shep. I see from your profile that you are an electrician so it looks like I have the right set of ears! As you say, it's not sounding major.

I've had ten years now of fantastic ownership and a few minor niggles don't detract. Still love it!

Nooo not a sparky but tinkered with my Tam for the last 7 years so lots of the common gremlins have cropped up once or twice. Process of elimination, logic and lots of patience!

[GaryF]

ninetynine said:

If you have air con probably trinity switch

Located trinary switch and disconnected. Hey presto, fan switched off. Have checked the connections and look ok.

Sounds like I need a new switch snd then an aircon regas?

[shep1001]

GaryF said:

Located trinary switch and disconnected. Hey presto, fan switched off. Have checked the connections and look ok.

Sounds like I need a new switch snd then an aircon regas?

I don't think they are servicable. I assume you plugged it back in to see if the fan started again? Cost about £30 for the switch then fitting & gassing. Remember it will need degassing first if you are going to fit it.

[GaryF]

Latest update... As trinary switch causing fan to stay on can indicate high pressure being detected in the aircon system (or faulty switch) thought about that and went for a blat tonight with the aircon on full puff for about 45 mins. Upon return home, problematic fan now off and stays off upon restart. This may be temporary, but hopefully not. Result!

Thanks all for your inputs.

[GaryF]

Final update in case anyone has the same issue in the future...

Driver's side fan started to stay on again (switches off when trinary switch disconnected). Aircon degassed, new trinary switch fitted and aircon regassed - problem fixed.

Helped that I took it to a specialist auto electrician / aircon chappie as the new trinary switch came with two connectors rather than the original one so some splicing to be done. He was able to demontrate the switch and fan operating on and off correctly using the aircon machine to manipulate temp / pressure. Job done.

Costs: new trinary switch £20, aircon degas/regas + switch fitting £65.40. Not bad.