Wayward temp guage
Discussion
Hi all,
I''ve noticed that my temp guage has just started doing silly things. When stationary or under reasonable load the temp guage shows the kind of temperatures I''m used to seeing.
Then suddenly when pulling away *gently* the guage started to rise rapidly to about 120 degs. After about one second it falls rapidly to its normal value.
Now it''s started doing this whenever it''s on just-open throttle, even on the motorway.
Coolant level is fine, drive belt looks fine (can''t see any slippage), fans come on when stationary, no sign of overheating.
The speed it rises at (from 80 to 130 degs in 1/2 a second) makes me think that it has to be electrical. But I''m concerned in case it isn''t. Could there be an airlock in the head (I did the swirl pot test and it looks fine) or a sticking thermostat?
Anyone seen anything similar? It''s been great temp wise up until now.
Cheers
Xain
theres no way physically the temperature could move that amount in that time, so this will definetly be an electrical problem - try tracing the wire from the sender to the gauge, checking if its OK and not shorting on anything - if its OK, id try testing the sender - remove it and measure its resistance whilst dipping into hot water (from a boiled kettle), ensure the resistance rises up linearly and doesnt suddenly jump - at 90 degrees the resistance should be around 600-800 ohms - if its alot less than this, then youve got a duff sender - if its OK - then the chances are its a suppression problem - replace the suppressor on the coil.
hope it goes well
cheers
chris
Phew, thanks Fordy. It's in for a service on thursday anyway with Fernies, but I wanted to be a little more confident that it was an electrical problem.
I nearly had an accident on the motorway from watching the bloomin' temp guage and not the road. Silly boy!
Suppressor sounds like a good idea. Once thing I have tried it to rev the engine up in neutral (no problems) and to rev it up under load by slipping the clutch with the brake on. Again no problems. So it looks electrical from that point of view too.
Cheers
Xain
If Fernies solve the problem, could you post on here what it was - im interested to know - thanks.
good luck.
PS - how do you rate Fernies?? Have you been there before?? - im only asking as im taking mine there in a couple of weeks time - its either them or Henely Herritage, as far as i can tell Fernies have a better reputation and they're cheaper.
cheers
Chris
OK, whats a 'Swirl Pot' test. My 500 tends to stay at 90 when on a run, but rises to 105 - 110 when stationary / in traffic. The fans come on and both work, and there is plenty of fluid in the resevoir. It dosn't go back to 90 until back on free road again though?
Any suggestions?
Thanks,
Rob
Blimey, that's about 20 degs higher than the range on mine (when the guage is working).
By Swirl Pot test, I just meant that I topped-up/bled the cooling system the way described in Peter Beech's workshop notes. There was no air in the swirl pot.
I've noticed that my guage only starts going wrong once it's reached 95 degs. up until that point it's fine. Once it's gone over, it continues to misbehave even when the temperature drops back to 70. Wierd.
it's best if you don't rely on the gauge for actual temp as they are probably not calibrated. Note where the needle sits usually and if it alters over time then you have a problem. The gauge indicates temp in the swirl pot so it will be cooler than engine temp, but don't panic, as I said if it has always read this temp then it is most likely just an inaccurate gauge. xain I think you have found the temp sensor to the ecu, if this is buggered your tickover will be all over the place
Actually, on my 97 500 engine as apache said, it does seem to be on the swirl pot (thanks A)
There *is* a one terminal brass/green sensor in the place you mentioned, but it is not connected to anything. Did they just leave it there on the Serpentine engines to plug the hole in the casting?
Anyway, I'll try waggling the wires on the swirlpot sensor.
Cheers
Xain
The sensor on the swirl pot is the otter switch, surely. All this does is switch the fans on.
The temp gauge and ECU each have a sensor on the front of the block. To make sure you are looking at the right sender, if you disconnect it the gauge should jump to the end of the scale. If the gauge plays up when things get hot, it could be a duff sender or an intermittant electrical fault. You could confirm which, by measuring the resistance of the sender as the engine heats up. The resistance of the sender should change progressively, if it starts changing eratically you've found the problem.
Cheers,
Peter Humphries (and a green V8S)
quote:
Actually, on my 97 500 engine as apache said, it does seem to be on the swirl pot (thanks A) There *is* a one terminal brass/green sensor in the place you mentioned, but it is not connected to anything. Did they just leave it there on the Serpentine engines to plug the hole in the casting? Anyway, I'll try waggling the wires on the swirlpot sensor. Cheers Xain
Hmmm, but that's part of the problem. There are two senders next to each other , near the distro. One is an unused one-terminal job, the other is a two terminal job, which appears to be the ECU sender (when I disconnected it, the temp guage didn't change).
I thought the otter switch would be on the radiator... is that wrong? if so, where is the guage sender?
OK. The otter switch is at the base of the swirl tank also called the header tank. Its the one with the filler cap on it. If you are still in doubt remove the connector and short it out - the fans should come on provided the ignition is on. This is a good tip to get you home if your otter switch goes west.
quote:OK the above was complete b*ll*cks, memory's not what it use to be but now I've checked and here's the story. The otter switch is at the base of the swirl tank, pot, thingy, also called the header tank, its the one with the brass screw on top. The expansion tank is next to the radiator with the blue cap. The bit about shorting out the otter switch connector is right and is a top "get you home" tip. All the above is true for a 98 Chimaera 450 which should hold true for your Griff 500. According to the wiring diagram the temp. gauge is fed by a single blue/green wire. On a quick inspection under the bonnet this seem to go to a sensor on the engine just behind the distributor, which seems to confirm what others have said.
OK. The otter switch is at the base of the swirl tank also called the header tank. Its the one with the filler cap on it. If you are still in doubt remove the connector and short it out - the fans should come on provided the ignition is on. This is a good tip to get you home if your otter switch goes west.
I have it!!
Thanks guys for all the replies, it's damned hard to keep track of TVRs mods.
Anyway, the otter switch is indeed on the swirl pot, the ecu sender is on top ov the engine behind the ditributor, and the guage sender in on the front of the engine, underneath the distro. Rather well hidden, I only spotted it becuase of the blue/green wire (thanks!)
So there you are if you need it. Now today I'll find out what the problem is because Fernies are servicing it...
That means my ECU isnt connected to anything - i can see the sensor on top of the engine, and it has no wire connected to it - then i can see the blue green wire go to the sneder for the temp gauge under the distributer. Has anyone else got this sensor with no wire attached - i cant see that anything has broken off - there is simply no wire in sight for it.
cheers
Gassing Station | Chimaera | Top of Page | What's New | My Stuff