cooling fans work with shorted otter, but not in automatic

[LLantrisant]

i have a strange issue with my fans:

sometimes they work, most times not.

now the strange thing comes: each time (when they dont work) i´m shorting the otter, they both start working, means wiring and relay are ok. all connectors are corrosion free and sit tightly on their terminals.

precausionally i changed the the relay...no improvement
i also installed a new ground to the otter (original one comes from alternator, now i have used a bolt of the engine, near the swirlpot)...no improvement.
i tried with different (cheap, medium priced and high priced) otter switches, all with switching temperature of 92-87 ...no improvement

a bit strange isnt it?


its a 1993 400model, 2 fans, 1 relay, otter swtich in bottom of swirlpot, level in swirlpot complies with the recommendatios.

[Steve_D]

Is it not just a case of the water temp not being high enough?

You have mentioned all the things you have changed but not reported what temperatures you are getting or how you are measuring it.

Steve

[LLantrisant]

shortly after the fans should kick in the pressure cap on the swirpot relaeses pressure

when they come on automatically, which is quite rare, the temperature is around 90.

if the temperature climbs over 90 i immediately know "fans do not kick-in"

[QBee]

I am thinking faulty otter switch. They are about £15 from your local autospares indie. You just need to decide what temperature you want it to come on/go off.

[LLantrisant]

qbee: read my opening post please carefully.

cannot be the otter switch....all tested ones randomly work...

[Classic Chim]

You need Rover gauge so you can see the Ecu water temp ! Airlock would encourage a lower boiling point so that’s where I would start.

Edited by Classic Chim on Thursday 20th June 07:04

Edited by Classic Chim on Thursday 20th June 07:08

[nawarne]

Classic Chim said:

You need Rover gauge so you can see the Ecu water temp ! Airlock would encourage a lower boiling point so that’s where I would start.

Edited by Classic Chim on Thursday 20th June 07:04

Edited by Classic Chim on Thursday 20th June 07:08

^^What Alun said. From your initial post..."shorting out/bridging otter-switch terminals and fans start" ….would indicate a faulty otter. Other random behaviour would say to me that you have air in the system.

Nick

[Penelope Stopit]

OP states various new otters fitted and they make no difference. Surely = No water around otter

[LLantrisant]

hmmm...even it sonds logic, it also sounds strange.......as each time i check the level inside the swirlpot there is plenty of water......where should it go during driving?

i would not bother you if the problem would be such easy.

temperature is simlar checking with rover-gauge....so the temperatures in the cooling system are indicated correctly...means there is "enough" temperature in the system to (theoretically) activate the fans.

by the way: all the otter switches where tested parallel in other cars....there they work......

summary:
otter switches are ok, wiwring is ok.

conclusion: airlock

but swirlpot is full

conclusion: confusion!!

Edited by LLantrisant on Thursday 20th June 10:09

[Classic Chim]

LLantrisant said:

hmmm...even it sonds logic, it also sounds strange.......as each time i check the level inside the swirlpot there is plenty of water......where should it go during driving?

i would not bother you if the problem would be such easy.

temperature is simlar checking with rover-gauge....so the temperatures in the cooling system are indicated correctly...means there is "enough" temperature in the system to (theoretically) activate the fans.

by the way: all the otter switches where tested parallel in other cars....there they work......

summary:
otter switches are ok, wiwring is ok.

conclusion: airlock

but swirlpot is full

conclusion: confusion!!

Edited by LLantrisant on Thursday 20th June 10:09

Airlocks can move from one point to another and often congregate at the top of the engine towards the rear in the inlet manifold area when cold I believe.

If water keeps bubbling up and pushing out I’d possibly be looking at a sniff test on the water system if air locks have been dispelled.
I presume your heater gets very warm when it’s upto temperature. It’s a simple process to bleed the water system but not always easy to expel all the air out the system, I find once the thermostat has opened and it’s flowing I rev the engine to about 4000 revs quite a bit to increase water speed and push last bits of air out and into my filling pot.
As yours is an older car I can’t remember if you have a bleed tube on the inlet manifold, this should be opened and connected to a pipe and into your half full filling pot in your swirl tank as you bleed the system allowing water and trapped air to circulate and be removed, just some info that you are probably aware of but always good to be sure

[LLantrisant]

my car is one of the first models (1993), yesterday evening, when i came home from a drive, i let the car cool down a bit, de-pressurized the system and changed the otter.

when removing the otter a huge stream of (f*cking hot) water flow out the swirlpot.(over my hands)..so stationary and depressurized the otter was definately fully covered.

heater is working perfectly, by the way.

Edited by LLantrisant on Thursday 20th June 12:54

[LLantrisant]

update from today:

i topped up some coolant, just to be on the safe side, let the car warm up with open swirlpot cap.

once the thermostat is open a nice stream of water was comming out of the top-inlet into the pot.

i closed the cap, let it gain more temperature...fans kicked-in correctly but only stop when the car has movef at least 500yards.

when again stationary i had to wait another 1-2 minutes....fans kicked in again, but in stationary condition they dont stop (at least not in the 3minutes where i waited until driving again)....once driving, around 500yards fans stop and remain stopped until i´m again stationary for a certain period.

so today it looks ok to me. there might be really been an airlock....hopefully gone now.

car is still running the original radiator, by the way, no shiny alloy upgrade.

[Classic Chim]

1993 very cool

I’m sorry I can’t remember but does your rad have cowls to help draw air through as I’ve read some early cars don’t have them but that might be Griffs!
I was going to say maybe your rad is actually the issue, slightly blocked or something,,, it’s 26/7 years old which is very impressive.

[wuckfitracing]

Fans should switch off when car is stationary. Either radiator is past it’s best or you need to make a shroud around the current fans to draw more air in. My 93 430 was the same in traffic until I changed rad and made a better fan shroud/mounting.

[wuckfitracing]

[LLantrisant]

no shrouds present.

obviously the rad would profit from an upgrade, even i think it might have been re-cored n the past...but who knows? as long as the fans keep the engine safe from overheating i´m fine for the moment

by the way: the car has 97.000miles on the clock

Edited by LLantrisant on Thursday 20th June 14:21

[Classic Chim]

LLantrisant said:

no shrouds present.

obviously the rad would profit from an upgrade, even i think it might have been re-cored n the past...but who knows? as long as the fans keep the engine safe from overheating i´m fine for the moment

by the way: the car has 97.000miles on the clock

Edited by LLantrisant on Thursday 20th June 14:21

Earlier on you say water is being pushed out via expansion cap so I’d say it’s not safe but you know your car.

[LLantrisant]

yes....when the fans did not kick in it overheated...but thats normal, hence the overpressure-release via cap. so nothing to worry here

by the way: the car has still the "old" style grille (with restriced airflow) fitted...not bad with 97.000miles

[Belle427]

Its quite easy to wire in an override switch should you wish to.
Bring 1 cable back from the otter to a switch inside the cabin and connect the other side to earth.
I utilised the dash light off switch as i dont use it.
I find it handy to use as a test button just to check fan operation.

Edited by Belle427 on Thursday 20th June 17:27

[Penelope Stopit]

As above, you could do this


It's explained here https://www.pistonheads.com/gassing/topic.asp?h=0&...