T O P
AutoModerator

Thanks for posting on /r/MechanicAdvice! This is just a reminder to review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). If you are here asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **If this post is about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ If you have tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*


Gasman0187

There should be 2 fans. One is a cooling fan that should kick on at a set temp. The other is the AC fan that should come on as soon as the AC is on. If the main cooling fan is not coming on then when you turn the AC on that fan is doing an adequate enough job of cooling the truck. It most likely will not as the outside temp rises. Check your fuses and relay to the cooling fan. If they are good get the truck up to temp and test the hot wire to the cooling fan with a test light. If you have power your fan is toast.


axe81

In addition to this, some older vehicles with electric fans used a different temp sensors for the dash and the computer. If have access to an OBDII scanner that reads data it might be worth A look to see if the computer is getting an accurate temp to turn the fans on. Compare it to the dash gauge for quick reference. They default to -40 if the sensor does not read


Gasman0187

True. Didn’t think about that. Had that same issue recently with a Ford Ranger. The dash and the Zeus were completely different. Ended up being a bad temp sensor. Good call.


axe81

Biggest reason I remember it is my Subaru has 2 temp sensors right next to each other (both a bitch to get to) and they didn’t use the same one until 2006


2006Silver

Hello, My 06 Silverado overheats unless the A/C is on. Coolant appears full, needle never moves if the A/C is on, even when towing in traffic. I haven’t seen the fans come on without AC. The truck coolant temp climbs above 220*F No obvious codes/check engine light either. Thanks for your advice!