Originally Posted by
fc735
i only use the mopar one, although the NAPA unit is a reboxed OEM part. NEVER use anything from AZ for electrical.
this is a PWM controlled relay, they have a penchant for burning up the drivers if there is too much draw. its basically a solid state relay. will set a CEL and cause multiple other issues if you try to rig in a standard ISO relay.
they fail for a reason:excessive current draw. every one that comes in and i diagnose as needing a fan relay gets a current ramping done of the fan, and almost every one of them has a fan that is going out drawing too much current.
it is very common for them to need both a fan and the relay, and i have never had one come back for repeat failure. not only on the grand cherokees, but also on the caravans.
it really bothers me that there are so many techs out there that do not bother to check the current draw of a circuit to determine why something failed, instead of blaming "inferior parts". and yes, most dealer techs do not even check the fan draw, cause "they aint paid to". there are multiple tech tips on Identifix, ALLDATA, and MOD, yet people do not want to read and learn.
Yes, the CEL P1491 is how I know it is going out every time. The fan is cheap enough I think, I will order a new fan and install that in the next few weeks. Damn thing cost me $61.00 today, it was $35 last time I got it. I have had this Jeep for 2 years, and I have had to replace the relay 4 times, replace the radiator once, now the radiator has another slow leak in it. I tried some stop leak, will see how that works. Its like this car just wants to be constantly in a state of almost overheating.