Relays Overheating?
09-20-2015, 03:10 AM
#1
Racer
Thread Starter
Relays Overheating?
Hello. New guy here. I have an issue where after about 20 minutes of running, the engine dies and I've noticed all the relays are very hot to the touch. After they cool down for a while, the engine will fire up again.
My car has recently had the CE replaced by a mechanic. I've read in a few places that corrosion and electrical resistance can cause this on other cars. Seem likely? It doesn't make sense to me, since I would expect corrosion to produce heat at the point of resistance rather than inside the relays themselves, since the relays would have low voltage and reduced current. The guy I talked to at the shop thinks it might be a grounding problem, but I would think that would also just cause low voltage or just an open circuit. Is a short circuit more likely? Also, my ABS light has come on, and sometimes it flickers when driving over bumps, which obviously seems like either a loose connection or a short circuit. However, replacing CE may have caused multiple problems.
The shop owes me a warranty repair, but it would be nice to save a trip and learn a few things. Thanks.
It's a 1986.0 5-speed.
My car has recently had the CE replaced by a mechanic. I've read in a few places that corrosion and electrical resistance can cause this on other cars. Seem likely? It doesn't make sense to me, since I would expect corrosion to produce heat at the point of resistance rather than inside the relays themselves, since the relays would have low voltage and reduced current. The guy I talked to at the shop thinks it might be a grounding problem, but I would think that would also just cause low voltage or just an open circuit. Is a short circuit more likely? Also, my ABS light has come on, and sometimes it flickers when driving over bumps, which obviously seems like either a loose connection or a short circuit. However, replacing CE may have caused multiple problems.
The shop owes me a warranty repair, but it would be nice to save a trip and learn a few things. Thanks.
It's a 1986.0 5-speed.
09-20-2015, 03:41 AM
#2
Drifting
Hi New guy , the three relays on a 1986 928S that will stop the engine at any time "When " the relays get too old ( meaning more than 10 years old) are }
Fuel pump relay
Ignition ECU power up relay
Fuel injection ECU power up relay
And yes the originals do get hot to touch ( as you have found ) and all relays that are that important and are more than say 10 years old are at risk of becoming unreliable
Note } the fuel pump relay ( example ) gets hot to touch because of the amperage it has to cope with
If they are the original 1986 relays ( 29 years old ) then get new ones , you will see a date stamp on the side of the old original relays
Fuel pump relay
Ignition ECU power up relay
Fuel injection ECU power up relay
And yes the originals do get hot to touch ( as you have found ) and all relays that are that important and are more than say 10 years old are at risk of becoming unreliable
Note } the fuel pump relay ( example ) gets hot to touch because of the amperage it has to cope with
If they are the original 1986 relays ( 29 years old ) then get new ones , you will see a date stamp on the side of the old original relays
09-20-2015, 04:15 AM
#3
Racer
Thread Starter
Yeah, that makes a lot of sense, thanks. Is the fuel pump relay the most likely culprit since my problems start while the engine is already running? Also, the tach drops to zero immediately when I lose power (while the clutch is engaged and the vehicle is still rolling). So it's like the tach gauge is immediately losing power. Might be an additional clue.
09-20-2015, 04:59 AM
#4
You can call me Otis
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Several systems use the same type of relay, including the fuel pump.
Replace all of the 53 relays, and clean all of the grounds.
53 relays cost about $5,.
Its the best place to start trouble shooting.
The most expensive single part I have bought was a used flex plate, about a hundred bucks.
(not counting the fuel pump, or brake rotors)
Replace all of the 53 relays, and clean all of the grounds.
53 relays cost about $5,.
Its the best place to start trouble shooting.
The most expensive single part I have bought was a used flex plate, about a hundred bucks.
(not counting the fuel pump, or brake rotors)
09-20-2015, 12:58 PM
#5
Racer
Thread Starter
Yeah, I have some 53's from 1984 in there.
Think I fixed it though. Swapped the starter relay with the fuel pump relay, and now the fuel pump relay barely gets warm. Looks like my problem is actually a loose socket. The replacement relay is a bit smaller and I can insert it better in spite of the play. The old one must have been arcing, causing the heat. Guess I'll have to pull the CE board and at least make sure I can seat the relay properly.
Think I fixed it though. Swapped the starter relay with the fuel pump relay, and now the fuel pump relay barely gets warm. Looks like my problem is actually a loose socket. The replacement relay is a bit smaller and I can insert it better in spite of the play. The old one must have been arcing, causing the heat. Guess I'll have to pull the CE board and at least make sure I can seat the relay properly.