Temp low, fans on!

[richy759]

I have a strange problem (possibly more than one) which I'll try to explain, and hope someone can help with.

I have checked the coolant level which is fine, the car seemed to heat up ok with the temp gauge rising as you'd expect up to about 80.
So I was going along the motorway and my Chim was reading 50 on the temp gauge, I slowed down to a roundabout and it seemed the fans where on already. The temperature began to rise then up to about 85 and stayed steady with the fans staying on. So I carried on back to motorway speeds and the temp dropped again to about 50-55. Got to my junction and when I stopped I noticed the fans where on.
I parked the car up and turned it off but then put the ignition back on whereby the fans stayed on for a minute or 2 and went off.

Can the otter switch get sticky and stay on for too long?
Could the fans be coming on while I slow down from speed? (sounds a bit far fetched to me)
When I turn on the ignition the fans don't come on.

it's a '98 500.
Sorry about the long rant, just wanted to get the whole experience across, any help would be appreciated.

Rich

[Dave 500]

Sounds like a bust sender or temp gauge to me. Well they would be first on my list of things to look at anyway. My temp sender went last year TVR Car Parts sell them for around £20.00.

[GreenV8S]

Could be the otter switch, or the relay. If you pull the wires off the otter switch and the fans keep running it's not the otter switch.

[richy759]

Dave 500 said:

Sounds like a bust sender or temp gauge to me. Well they would be first on my list of things to look at anyway. My temp sender went last year TVR Car Parts sell them for around £20.00.

Maybe I'll replace it just in case then, this doesn't explain the fans being on prematurely but that could be another problem...

Rich

[richy759]

GreenV8S said:

Could be the otter switch, or the relay. If you pull the wires off the otter switch and the fans keep running it's not the otter switch.

Cheers GreenV8S, I'll have a go tomorrow.
Forgot there was a relay controlling the fans too, why are there 2 methods of controlling the fans, just in case?

Incidentally I changed my battery the other day and took a pic of the relays and fuses, I can't match my setup up to any in the bible
My manual shows the 6 + 5 arrangement but that not what I see.

fuse layout

Rich

Edited by richy759 on Wednesday 8th August 22:53

[Ribol]

richy759 said:

I parked the car up and turned it off but then put the ignition back on whereby the fans stayed on for a minute or 2 and went off.

Not much wrong with that in itself, if it is hot enough but the time you come to rest.

My car has a relay for each fan so if yours is the same you can rule out the relay side of things if both fans stay on. Otters tend to not work at all(as in fans don't come on at all) when they go wrong, rather than mess about temp wise.

Maybe the otter you have fitted is simply the wrong temp range, someone may have fitted it in an attempt to cure(or to prevent) overheating problems?

[richy759]

Ribol said:

richy759 said:

I parked the car up and turned it off but then put the ignition back on whereby the fans stayed on for a minute or 2 and went off.

Not much wrong with that in itself, if it is hot enough but the time you come to rest.

I was using this as an example of the car acting normally
The otter switch has been in there since I bought it and it was acting fine then... I think.. *madness sets in*
I always pay attention to the gauges so I'm pretty sure it's a new thing.

Good point about the individual fan relays, if only I could match up my relay panel with one in the bible (see above).

Rich

[Ribol]

richy759 said:

Good point about the individual fan relays, if only I could match up my relay panel with one in the bible (see above).

Different fusebox to mine for sure, but if there are two relays on your car I would bet on the two yellow ones middle row next to the black one, both the same way round and together.

Usual disclaimers apply

ETA the efficiency of the rad core changes quickly with age on these cars so that might also be something to consider.

Edited by Ribol on Wednesday 8th August 23:16

[spend]

The otter switch just grounds the relay(s) which power the fans - its not designed to switch 50a If the green/pink cable is grounding anywhere (eg in back of fusebox) it will be doing just what the otter switch does - unusual tho. Stick a new temp switch in first, at <£5 a spare is worthwhile anyway IMHO.

Dave

[Ribol]

spend said:

The otter switch just grounds the relay(s) which power the fans - its not designed to switch 50a If the green/pink cable is grounding anywhere (eg in back of fusebox) it will be doing just what the otter switch does - unusual tho.

You're kidding right?

[spend]

Only if it was your problem.

Dave

[richy759]

spend said:

The otter switch just grounds the relay(s) which power the fans - its not designed to switch 50a If the green/pink cable is grounding anywhere (eg in back of fusebox) it will be doing just what the otter switch does - unusual tho. Stick a new temp switch in first, at <£5 a spare is worthwhile anyway IMHO.

Dave

Where can I get a temp sensor for <£5 Dave? Clever trevor sells them for £17.

Cheers,
Rich

[spend]

richy759 said:

spend said:

Stick a new temp switch in first, at <£5 a spare is worthwhile anyway IMHO.

Dave

Where can I get a temp sensor for <£5 Dave? Clever trevor sells them for £17.

Cheers,
Rich

Temp/fan switch is generic term for otter switch, most motor factors stock a range of intermotor switches at various operating temps. Basically your fans should not be running whilst you are traveling in free air. Your gauge may be inaccurate, but this is not normal, and suggests a fault (although otters normally seem to fail to operate rather than sticking on). Cheap relays & otter can be replaced, and you have useful spares for the future IMHO.

Dave

[richy759]

Think I have found one from LRdirect (£5.23)
part ETC8496.
http://www.lrdirect.com/customer/product.php?productid=120831 

can anyone confirm it will do for my '98 500?

Rich

Edited by richy759 on Thursday 9th August 13:56

[Ribol]

richy759 said:

Think I have found one from LRdirect (£5.23)
part ETC8496.
http://www.lrdirect.com/customer/product.php?productid=120831 

can anyone confirm it will do for my '98 500?

Rich

Edited by richy759 on Thursday 9th August 13:56

Wrong one.

Just buy an Intermotor "50200" from any half decent motor factors, that exact one is working perfectly on my car.

[Griffit]

richy759 said:

I have a strange problem (possibly more than one) which I'll try to explain, and hope someone can help with.

I have checked the coolant level which is fine, the car seemed to heat up ok with the temp gauge rising as you'd expect up to about 80.
So I was going along the motorway and my Chim was reading 50 on the temp gauge, I slowed down to a roundabout and it seemed the fans where on already. The temperature began to rise then up to about 85 and stayed steady with the fans staying on. So I carried on back to motorway speeds and the temp dropped again to about 50-55. Got to my junction and when I stopped I noticed the fans where on.
I parked the car up and turned it off but then put the ignition back on whereby the fans stayed on for a minute or 2 and went off.

Can the otter switch get sticky and stay on for too long?
Could the fans be coming on while I slow down from speed? (sounds a bit far fetched to me)
When I turn on the ignition the fans don't come on.

it's a '98 500.
Sorry about the long rant, just wanted to get the whole experience across, any help would be appreciated.

Rich

Mine used to do this sort of thing all the time and I sorted out the duff readings on the gauge by using the spare temperature sender in the top of the block. If you do a search for spare sender you'll find loads of posts about this and plenty of help from David Beer. It's only applicable to serpentine engines apparently but with a '98 you shouldn't have any problems.

It's all to do with the location of the original sender meaning it doesn't always tell the truth. Apparently it's on the end of a piece of copper pipe that doesn't have coolant permanently flowing through it. When cruising the pipe gets cold, gets no coolant flow and the gauge drops right down, when you brake for the roundabout it suddenly warms up and tells the (TVR) truth... The spare sender on the other hand is in flowing coolant and tells something closer to the truth.

Do as David suggests and use the variable resistor if you can, the 120ohm on mine means the gauge over-reads by about 5 degrees or so I reckon.

It's honestly a two minute fix once you make up the little piece of wire with the plugs either end and resistor in the middle.

Good luck

[richy759]

The picture is getting clearer now, I always did hate cooling systems on cars.

I went out in it just now and it was acting fine. You can certainly notice the temp sender playing up and reporting low temps so thanks Griffit I'll have a look into using the other sender.
I took my DVM which has a temperature reader on it and measured the temp of the swirl tank which tied up pretty well with the gauge. I'll get hold of a new otter and wait till it plays up again and try some of the above posts ideas.

If the fans were getting stuck on, would running the car at low temps do any harm to it?

Thanks for all the help.

Edited by richy759 on Thursday 9th August 22:03

[GreenV8S]

Fans on will wear the fans out and could run the battery down, but they won't make the engine run too cold - the stat prevents that.

[V8 Animal]

Ribol said:

richy759 said:

Think I have found one from LRdirect (£5.23)
part ETC8496.
http://www.lrdirect.com/customer/product.php?productid=120831 

can anyone confirm it will do for my '98 500?

Rich

Edited by richy759 on Thursday 9th August 13:56

Wrong one.

Just buy an Intermotor "50200" from any half decent motor factors, that exact one is working perfectly on my car.

Is this the ecu temp switch does anyone know?
V8 Animal

[GreenV8S]

V8 Animal said:

Ribol said:

richy759 said:

Think I have found one from LRdirect (£5.23)
part ETC8496.
http://www.lrdirect.com/customer/product.php?productid=120831 

can anyone confirm it will do for my '98 500?

Rich

Edited by richy759 on Thursday 9th August 13:56

Wrong one.

Just buy an Intermotor "50200" from any half decent motor factors, that exact one is working perfectly on my car.

Is this the ecu temp switch does anyone know?
V8 Animal

'This'?

That link to lrdirect goes to a thermister termp sender as used for the fuel temp sender and ECU coolant temp sender. It's not an otter switch; it's not a sender for the temp gauge.