I recently had a problem with my truck turning off on the highway. It would crank back up but once it got home and parked it died and would only turn over. Had a mechanic come over and he replaced the IDM relay and it cranked and ran GREAT )Dead for over a month). My question is why would the relay blow stop working? If it's a short where do I even start.

 

The 6.0 has a FICM not an IDM. Relays can just fail, they are a mechanical part. So what your saying is right now you have replaced the FICM relay, it ran for a little bit, now it just cranks. Correct?

 

Besides the fact they are mass produced and sometimes a weak one will slip by and fail prematuerly. You need to start checking your wireing to find a possible short.

 

You are talking 6.0 right? check the FICM connections make sure they are snapped in all the way, the clips will break so may need to Zip tie them.

 

Do you have any Gauges ? also look at ICP, ICPV, IPR

 

post the year

X-2 gauges^^

 

Relay failure could be because of loose connections in the BJB (Battery Junction Box)
where the FICM relay is located. A loose connector tends to get worse do to the fact that
is it loose and will have some heating do to current and higher resistance at that
connection. You need some type to tool ie a gauge set that will read live data so you
can see what the numbers are for each thing that would need to be checked and verified.

FICM main power being one of the things along with logic power and so on.
If the FICM is not getting main power or battery voltage then it's back to the relay or
the connector plugs.

Sean

 

No it ran fine and randomly shut down on the highway. It started back up and drove home then it cut off right when I parked it. At that time it would only turn over. It sat for a while until I could get a mechanic out to look at it. The last resort he tried was to swap the blower relay with the IDM and then it started right up. When it was running my AC wouldn't blow anymore so that prooves the one that he swapped and put in the blower spot is broke. But why would any of that even happened? I know relays can fail but it's like this one sometimes worked and sometimes didn't. It was the original relay in that spot I believe. 280,000 miles

 

That's the weird part though. Once he replaced that relay it worked fine. Since I'm confused on what relay it was, it's the relay next to the only gray relay under the hood.

 

2005 f-250
280,000 miles

 

It held up for 280,000 miles so it wasn't like it was brand new. Do relays just go bad over time? And even if they do how would that explain why it would die but start back up. Can they relay work sometimes and not?

 

Yes, they do go bad over time. Probably the FICM/IDM relay pictured here:

 

He swapped 302 and 303 and it started. Could a short cause a relay to go out?

 

Relays do fail. The contacts can "weld" themselves together or get build up on them and not make a good connection. The coil inside can also fail open from a broken or burnt wire inside.

Once you have replaced it with a new one crack it open and have a look see.

.

 

repeated closing of a relay into a faulted circuit can ruin the contacts. You would also have several blown fuses and such. I would replace the relay and call it good. I am an electrician by day and this sort of thing happens, anything mechanical wears.