General Overheat /Electrical problems

[MusicmanXXXXX]

Hi,

My Fiat Uno overheats. ALSO... the electrics cut out when I'm going along the road (but not until the engine has warmed up)... then cuts back in again... lights, radio, indicators etc., but not the power to the spark plugs so the engine comtinues.

Anyone got any ideas?

p.s. had one expert look at it to no avail. All the earth straps were checked and cleaned etc

Many thanks in advance !!!

Dave

 

[Chas Uno]

Hi Dave and welcome to the forum,

What model is your Uno? What engine size? Is it carb or fuel injection? A bit more info is needed to attempt a full diagnosis!

From the info you've given, it sounds like an earth problem. Have you checked the connections at the back of the fuse box?

Also, I'd recheck the battery cables and make sure they are all tight. Also check the smaller cable running from the battery + post as this supplies power to everything other than the big cable which goes to the starter motor.

Another place to check is the connections at the back of the alternator. Disconnect the battery first before tightening these up as a spanner can earth the + cable!

Very much a case of going over your cars electrics with a fine toothcomb to make sure all is in order.

Let the board know how you get on.

Chas

 

[Chas Uno]

Oh, and as for overheating, are you losing coolant at all? Check the radiator level, as if it is dropping then you could have a failed headgasket. Also check the engine dipstick. If the oil is creamy white then that's a sign the headgasket has gone.

Also, when does it overheat? Sitting in traffic or driving along? Does the electric fan come on? What readings are you getting from the temperature gauge?

Chas

 

[MusicmanXXXXX]

Hi Chas, and thanks for the welcome..

The Fiat is an UNO 60 "H" reg. It's only done 54,000 miles. Genuine two lady owners (if you don't include me!!)

The coolant remains at a good level.

It has a carb rather than fuel injection.

The fan does come on but I feel that it could cut in earlier.

It never used to overheat but since the MOT it's gone a bit haywire.

The temperature gague does peculiar things. Once warm, the guage tends to show above "normal" reading but (but not up into the red) and when I use the breaks the temp. gague flicks down to normal again. THEN when I switch the engine off the temp. gague zooms all the way round clockwise and remains pointing straight down!


I'll check the colour of the oil!!

Thanks Chas, and any more ideas will be greatfully received.

Cheers

Dave

 

[Chas Uno]

Dave, from the new information you've given the board it sounds more like you have an electrical fault.

If the coolant doesn't need topping up regularly, and also the oil level remains the same and isn't mixed with coolant it doesn't sound like a head gasket problem.

The fan on most Uno's should cut in at about the half way mark, about 90 degrees centigrade on my mk 1.0 FIRE. Normal running temperature should be 80 degrees, or somewhere between 70 - 90 degrees (1/3 to 1/2 way) unless it is very cold. Mine rarely goes much above the halfway mark except on very hot days, but even then the fan kicks in and doesn't allow the engine to go much beyond this.

Quote:

***

The temperature gague does peculiar things. Once warm, the guage tends to show above "normal" reading but (but not up into the red) and when I use the breaks the temp. gague flicks down to normal again. THEN when I switch the engine off the temp. gague zooms all the way round clockwise and remains pointing straight down!

***

From this information you need to check whether the engine is actually overheating or if you are getting faulty readings. It sounds to me that your engine is fine and it's the readings that are fault.

The fact that you say when you use the brakes it affects the temperature reading almost certainly suggests an earth problem in the car or in the dashboard. Plus, when you switch the engine off and the gauge shoots to the right instead of the left shows an earth problem or that you are still getting a live feed to the dashboard.

It's worth checking the battery cables again (both ends - also the one that goes into the back of the fusebox), plus the engine earth strap and the connections to the alternator.

Check the ignition switch wiring. The switch that bolts to the ignition key housing can fail and give weird electrical problems. Does wiggling the key with the electrics on make any difference?

I'd also check the push in wiring loom connections at the back of the fuse box.

Lastly I'd check the connections to the instrument pod. If it is only the temperature gauge that is behaving badly then it's possible that the gauge itself might be faulty.

But as you mentioned in your first post, if ALL the electrics cut out except the engine this suggests that there is a supply/ earth problem to the dashboard/ rest of the cars electrics. It almost certainly sounds like a loose connection or earth fault.

Let us know how you get on and if you manage to locate the fault!

Chas

 

[F R O S T Y]

I was going to say everything that Chas has suggested but i might add that if your car overheats with no obvious leaks it may be doing so under pressure. Basically while your driving it might be leaking coolant through a crack in the header tank or a hose somewhere. I had this same problem a while back, i was baffled because the car would not show obvious signs of a leak when it was not moving but only whilst driving water vapour was escaping from a very tiny crack in my header tank. Other than that check your heater matrix for blockages and also the electric fan switch is a popular known culprit for overheating problems.

F R O $ T Y

 

[MusicmanXXXXX]

Hi Chas and Fro$ty,

Many thanks for the detailed, expert advice regarding my Fiat. There is much here to take in (let alone find under the bonnet). One useful thing is that I now have a Haines manual and will probably attempt some kind of remedial action over the Easter period.

Thanks again... I'll let you know how I get on

Dave