Fan relay's
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
That seems to be out of the norm. Most of the relays are lasting much longer than that if not the life of the car so far. The relay for the auxiliary fan (right side) hardly ever energizes unless you are pushing 240* on a regular basis.
Just wondering if the relay contacts are burning up or the coil is opening?
I guess there might be different manufactures of relays but have not gone down that road yet.
Just wondering if the relay contacts are burning up or the coil is opening?
I guess there might be different manufactures of relays but have not gone down that road yet.
Melting Slicks
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
The last Delco relay I bought from GM was China made. 
A Vette pal uses (just made one for me) a replacement, higher rated relay that he claims should go forever.
The sealed relay is a common NTE R51-1070-12, rated at 70A, versus the factory's 30-40A. Roy added a small diode across the switching portion to eliminate arcing which he states burns out the contacts on the Delcos. I see no reason why adding a diode wouldn't similarly help a stock relay.
The downside of the NTE relay (available and nearly any electronics store) is two larger lugs, part of the higher rating, which will not clip to the Corvette harness. I haven't found a plug, so four spade connectors are used. Roy epoxied a small mounting tab, with a hole to affix it in the stock place, with the stock hardware.
The banded end of the diode goes on the IGN switch side, the blue wire next to the red BAT feed in the early C4.
The upside is doing this once and that the NTE is totally sealed. I will make another one for my Corvette truck project.
The sealed relay is a common NTE R51-1070-12, rated at 70A, versus the factory's 30-40A. Roy added a small diode across the switching portion to eliminate arcing which he states burns out the contacts on the Delcos. I see no reason why adding a diode wouldn't similarly help a stock relay.
The downside of the NTE relay (available and nearly any electronics store) is two larger lugs, part of the higher rating, which will not clip to the Corvette harness. I haven't found a plug, so four spade connectors are used. Roy epoxied a small mounting tab, with a hole to affix it in the stock place, with the stock hardware.
The banded end of the diode goes on the IGN switch side, the blue wire next to the red BAT feed in the early C4.
The upside is doing this once and that the NTE is totally sealed. I will make another one for my Corvette truck project.
Last edited by whalepirot; Jan 7, 2010 at 10:38 PM.
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Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Even if you have a later 'vette that drives the relays from the ECM, the diode will reduce the load on the ECM, so the diode across the coils is a good idea for both fan relays. (The stripe on the diode must go toward the + voltage).
Thank You, veterans!
Last edited by Hot Rod Roy; Jan 9, 2010 at 04:08 PM.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
This diode across the coil of the relay eliminates arcing in the water temp sensor in the head, which assures a long life for the temp sensor. I installed on of these 70/80 amp relays in my '84 about 5 years ago, and have had no trouble since. The larger spade terminals on this relay solves the problem of overheated terminals in the stock relay connectors.
Even if you have a later 'vette that drives the relays from the ECM, the diode will reduce the load on the ECM, so the diode across the coils is a good idea for both fan relays. (The stripe on the diode must go toward the + voltage).
Thank You, veterans!
Even if you have a later 'vette that drives the relays from the ECM, the diode will reduce the load on the ECM, so the diode across the coils is a good idea for both fan relays. (The stripe on the diode must go toward the + voltage).
Thank You, veterans!
Not sure about the "fan" relay off hand but most of the relays in these C4 relays already have an internal resistor across the coil to reduce the bounce/surge.
A small metal oxide varistor (MOV) can also be used to take the bounce/surge out of the relay's coil to reduce the burn effect of the bouncing contacts on the other end of the fan circuit that is being open/ closed. Hook the MOV up the same way polarity wise as Hot Rod Roy suggests.
Last edited by engle1147; Jan 11, 2010 at 06:20 PM. Reason: I agree
opps should have been this 