Neill117
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| posted on 1/3/08 at 07:59 PM |
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Over heating but not!
Today I went out for a blast in my tiger. Its a pinto engined, polo rad and twin 40's with standard sierra transistor ignition and a newly
fitter omex speed system rev limiter.
The car warmed up as normal and then the temperature went a little high, up to 110/ 115C was being read by the gauge which gets its reading from the
head. So I pulled in to allow the car to cool. Normally about 90 tops.
I had assumed thermostat or something of the like but the fan was running and the sensor for that is rad mounted. After a minuite or so the
temperature dropped a little and the fan cut out. So rad must be <85 degrees But the guage read 100 degrees measured at the cyl head.
Before I pulled over I noticed that turning my lights off had yielded instant changes in the temperature gauge readout. When stopped with the engine
off i turned all the lights on and the temp rose to 110c and then turned all the lights off and read 100 degrees. I just don't see how that can
be right? no engine running = no heat. Sure enough turn the lights off and back to 100.
I waited until the car totally cooled to cold and tried again. No change to the temp gauge with lights on so only applicable hot. Also there was
allot of clicking from the dizzy, which has never happened before and stopped after about 10 secs after slowing down. The engine wasn't running
just electrics on to try and replicate the same phenomenon I found when hot ie +10deg with lights on.
I think the gauge is playing up but I would say contacts are ok as cold reads as cold. If its a measure of resistance i would expect it to only read
20 deg+. Its just weird that it has just started after I have fitted the Omex and why electrical load seems to be an important factor.
The only thing i could think of was some sort of interference affecting the reading?
Has anyone else had this problem if so how did you fix it? i would like to get my gauge back to being an accurate representation of engine
temperature.
I am sure the limiter has had an effect and don't believe it is cooling related as the fan cutting off just after stopping is normal. and
suggests to me the whole system should be about the same temp.
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owelly
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| posted on 1/3/08 at 08:12 PM |
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I would try using a piece of wire with a croc clip at each end and eath the gauge, then the lights then the block etc to see if there is a path to
earth through the lighting circuit, or the dash lights.
http://www.ppcmag.co.uk
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mark chandler
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| posted on 1/3/08 at 09:41 PM |
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You need a voltage regulator in circuit, these drop the volts to gauges to around 10v constant so tre battery voltages get ignored.
All your gauges are proablly reading high all the time, they will just go up futher with the engine running and drop a bit when you apply load like
lights etc.u
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nitram38
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| posted on 1/3/08 at 10:00 PM |
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Do you know anyone with a digital thermometer? (laser type).
You can diagnose a lot of problems on a cooling system just by pointing it at different parts.
If your cooling system (thermostat) is working properly, then as suggested, you could have some sort of voltage problem.
Although a regulator would help, if it worked before, then I would be taking a look at a fault alternator regulator.
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Schrodinger
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| posted on 1/3/08 at 10:37 PM |
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If they are Tiger dials then they should not need a voltage regulator and IIRC they are ETB guages. ETB themselves a re a very friendly and helpful
lot.
Keith
Aviemore
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02GF74
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| posted on 2/3/08 at 08:56 AM |
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quote:
Originally posted by Neill117
Also there was a lot of clicking from the dizzy, which has never happened before and stopped after about 10 secs after slowing down.
you hear this when you have stopped? and engine is not running?
if engine is not running, then it won't be mechanicl i.e some rotating part hitting something else so presmably it is somoeting else - can it be
arcing? or is it the click you get when hot items cool down?
sounds (pardon the pun) most strange.
firslty undo the last change i.e. disconnect the rev limiter and report back.
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David Jenkins
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| posted on 2/3/08 at 10:07 AM |
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quote:
Originally posted by nitram38
Do you know anyone with a digital thermometer? (laser type).
You can diagnose a lot of problems on a cooling system just by pointing it at different parts.
Neil,
Whereabouts in Essex are you? Cos I've got one of those remote digital thermometers... I'm just over the border in Suffolk.
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Neill117
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| posted on 2/3/08 at 03:25 PM |
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Cheers for the replies chaps I have just been trying a few bits and bobs out....
The clicking did not happen, this time, until i was inspecting the temp sensor, engine off and hot. When I picked it up there was a clicking like a
relay firing repeatedly. When I put it down nothing. This lead is taped to the hall sensor pickup so I think the clicking is going to end up being a
poor connection in the hall sensor line.
I disconnected the omex unit totally from the Coil low voltage leads and earth so the unit was completely isolated and allowed the car to warm up.
The temperature rose to an indicated 105C then the fan cut in and cooled down to an indicated 90ish degrees with the engine running. I allowed this
cycle to complete 3 times to check this pattern. It occurred exactly the same. I now think this is not an electrical problem and must be a restriction
in the cooling system. Maybe the thermostat is not opening fully? and the omex is a red herring.
Incidentally with the omex disconnected I turned on the lights and when hot the temperature springs up by 10 degrees.
I measured the voltage through the temp sensor lead cold and it was 7.7v cold rising to about 8.6 hot. The gauge is also not equidistant between
marking so I do not believe the sensor scale to be linear, which could corroborate marks point about a voltage regulator as the slight change could be
worth more hot which is why a 10 deg swing but only when hot. so probably now a new problem per se just one I have not noticed. Gauges are from ETB
but VDO items.
I also disconnected the sensor lead and connected a new one that ran around the garage, to bypass and EM sources that may have been inducing a voltage
and the same happened +10deg when hot with the lights turned on. So have convinced myself the variation is no fault of the sensor.
David, I am in Chelmsford so I guess about an hour away from you. I will have an ask at work tomorrow and see if i can borrow one. Thanks for the
offer though.
I think I will examine the cooling system for restrictions, check the hall sensor lead for shorts and reconnect the omex as it seems to have no
notable impact.
[Edited on 2/3/08 by Neill117]
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Neill117
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| posted on 3/3/08 at 07:55 PM |
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I called ETB today who suggested I looked at the gauge earth and the engine earth. Both are earthed adequately and I have a large earth strap between
the engine and battery. Gauges are also earthed well.
Anyway, I tested by wrapping wire round the sensor and taking that to the battery and the gauge earth straight to the negative terminal.
During testing if I removed the new earth straps the temperature rose slightly so I believe a good earth is very critical and could explain the
slightly higher temperature the fan was kicking in at as iI had disturbed the earth when I came to fitting the Omex as I earthed that at the same
point maybe making the connection worse and upping the reading.
When I turned the lights on with the improved earth there was no movement. Both new wires seem necessary to achieve this though as removing either saw
slight movement.
As a result I will be getting some gold terminals and copper wire and earthing the sensor and gauge directly to the battery. It may seem overkill but
my testing has highlighted to me that this is a very sensitive circuit.
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