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Discussion Starter · #1 ·
Motor vehicle Electrical wiring Vehicle Automotive tire Gas



What are these relays on the drivers side inner fender?
 

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Those are likely relays for the ESOF system. They control the motor on the transfer case. Might be daytime running light relays if you have that system.

on edit: just say you have a 2WD truck, so not ESOF.
 

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Aren’t those for the trailer lights?


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Good question. As I was looking around trying to troubleshoot a few things I saw these 2 relays in their own box.
 

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Discussion Starter · #5 ·
I have 2wd. Maybe they are for trailer lights.
 

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Isn't one of those the ac compressor relay?
 

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Isn't one of those the ac compressor relay?
I think you're correct that it's for AC, but for the magnetic compressor clutch. The two smaller relays appear to be trailer tow turn signals (left and right).

The 99-01 trucks have a 2-relay box for Trailer tow battery charge and backup lights. Only gas trucks in those years have an AC clutch relay.

Here's a diagram from the service manual. for the 02's
 

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