FP relay fail...

[Treebreakerbob]

Originally Posted by Farwest

These relays I am discussing are the 'recall relays'....not the original inbiult TIPM relay...when I moved the first recall location and replaced the Factory fitted OMRON recall relay with an OEX, because I couldnt get the forum recommended Narva relay here in Outtahixville....the internal wiring diagrams for both were identical...the relay southerncomfort has bought and fitted...which is the forum recommended Narva relay...is a different type of relay...thats the basis of my question into the differences between a 'constantly open' and a 'change over' relay...its a simple question to those that know...I simply dont know and would like to learn/understand the difference...wont change the World, but will educate me in what Im dealing with

Constantly open or normally open means the incoming power feed (pin 30) is an open circuit, it does not connect to any thing until the trip current is applied, then it normally goes to pin 87 and on its way to whatever. Change over is the incoming feed pin 30 is connected to pin 87a and current flows out, when the trip current is applied it moves the contact to pin 87 away from pin 87a

As our relays only use four of the five pins 85 & 86 trip current to earth then 30 live power feed and 87 power out after trip current is engaged, there is no connection for 87a wired into the base, that’s why a four pin relay will work

The only reason to use a five pin change over relay is it would tell you when the trip current failed or was not activated (through a light or sound alarm, good for diagnosing ) but it would be on all the time the engine or ignition is off as our power feed is wired into the plus terminal in the tipm

Clear as mud hey?

Bob

[Lazy-Ferret]

Wot-e-sed! [emoji6]

Here is quite a good site for the info you asked for.

https://www.12voltplanet.co.uk/relay-guide.html

Basically it explains the main differences, which boil down to
Operating Voltage & coil resistance
Switching current
Pin outs (connections)
& if they have a built in fuse/resistor/diode.

I take it Jeep use a Resistor Relay, as they can't rely on their techs to always connect it up correctly, as a Diode Relay would be far superior, if the control feed to the relay and the ground are the correct way round. Unfortunately a relay will work quite happily with the wires reversed, and the only clue it was reversed will be a small puff of smoke, and a slight burning smell the first time it was used, where the Diode burns out, but after that it will appear to work normally, just with a huge risk of dammage to the ECU.

The Resistor/Diode in the relay is there to stop a reverse current being sent back to the control unit that can cause damage to electronic components when the relay is switched off.

Sent from my SM-S908B using Tapatalk

[SouthernComfort]

I never saw the first recall relay itself. I had no reason to look at it since it hadn't given me any problems by the time I took it in for the second recall. All I know so far is the second recall relay has an identical pin and wiring configuration to the Narva 28 Standard with resistor, which is why I chose that one as opposed to the 44 'change over' type. The question is, why would Jeep have changed the 'type' of relay to the original tipm relay at the first recall, if indeed they did? As I understand it the recalls were only about relocation, not necessarily changing relay type.

[SouthernComfort]

The answers must be hidden in the mist somewhere. One day the mystery may be solved, but for now I agree the 'couple of working spares in the boot' is a liveable solution.

[drover]

Did I mention I found the fuel pump relay hidden in the TIPM on the 2015 wagon, looked all over for it with no luck but found it on the fuel heater circuit, its a mini one hidden under the board, fuse 70, when I get time or bored enough I will print out diagrams and see if I can trace the circuits and maybe find any changes............... don't hold your breath on it as I think it will be a pain to do......

[drover]

The board in the 2015 is 2 versions after yours @Farwest, so gets me thinking it may not be just the relay but some cock up they did in the board itself for I assume your relay and mine may possibly be the same.......... again I might follow it up one day..

[Treebreakerbob]

Originally Posted by drover

The board in the 2015 is 2 versions after yours @Farwest, so gets me thinking it may not be just the relay but some cock up they did in the board itself for I assume your relay and mine may possibly be the same.......... again I might follow it up one day..

That would answer the question why some cars like mine eat relays for breakfast, however had no problems with the original tipm relay or the first recall relay for some years then even the first Omron relay which I replaced with another Omron relay started failing in quite short distances

Could be a voltage leak on the trip circuit causing the contacts to arc a little till they fail?

Bob

Ps I had no idea the first recall ones were change over but I should imagine a change over one would be more durable as all the pins have use imho