Tachymetric Relay Getting Very Hot

[lagonda 42]

Not long after I bought my CTi (2003), the tachymetric relay failed..needless to say at the furthest point on the longest journey. Bought a new one, drove it home. A little later, I found the only problem with the original (Cartier 02 474) was that one of the pc board solderings was a dry joint. Cleaned that up, resoldered it...and kept it as a spare.

 

The replacement I bought was a Hella 4RP 008 189-11, which has also worked fine.

 

The bloody jerky-jerky has slowly returned, and the Cartier one having failed (dry joint again, resoldered today!), been running on the Hella relay. Yesterday the misfiring was really bad, didn't want to idle so I really need to get this sorted.

 

I've noticed that the relay can get too hot to hold quite quickly, and particularly that the terminal numbered on both relays, has got so hot that the surrounding insulation has melted...on both relays. Unfortunately I can't say which feed goes to terminal 87 as with classic French logic, the Haynes manual wiring diagram wiring codes show completely different numbers to those on the relays. If it helps, if you look at the terminal end of the relay, and have the 3 vertical pins in a row at the bottom, then terminal 87 is crossways at the top.

 

So....is it normal for these to run so hot, or could this indicate an electrical fault elsewhere? Do these relays age and expire? Is there a make of relay that doesn't fail like these?!

 

Makes me laugh at the reputation Italian cars had for dodgy electrics. I ran Fiats and Lancias for over 25 years with nothing more troubling than a dodgy earth to a rear light. The CTi is a better car, but the electrics are total crap!

[welshpug 1,666]

iay be high resistance form the dry joints or a large draw from a failing fuel pump.

[lagonda 42]

Fuel pump was replaced, but only I think 2 or 3 years after the car was new, in 1989. Mileage is now 216,000, how long do these pumps normally last?

 

Just had a look under magnifying glass at the innards of the "new" Hella one...dry joint spotted and now resoldered. Needless to say, one of the two joints from the "87" pin.

[lagonda 42]

The tachymetric relay was still getting hot after that, disappointingly. I found you could turn the relay round and insert only pin 87 in its socket in the plug...and it was pretty loose. Eventually I managed to close up the contact areas in the socket terminal, by pushing a thin screwdiver down past the wire and twisting the screwdriver. Relay less hot now...and now I've swapped the AFM for one that works properly, it's just getting warm, so perhaps the faulty AFM was playing a part by providing intermittent signals.

[Slo 283 1 Cars]

It will be bad wiring mate