My truck builds heat at idle with the A/C on. The temp steadily rises to 210 at which point I lose my nerve and open the windows. Any engine speed above 1200 RPM resolves the situation and temps fall back below 200. Electric condenser fans run normally with A/C on (though frankly I'm not sure how effective they are at the age of 20 years).

I bought myself one of the fancy IR thermometers with the laser sight and last night took some readings of different areas of my radiator. This is what I found....



So, what next? Does this look like a radiator that is clogged or restricted, or a radiator that is doing its job?

 

sure looks to me like your rad is operating properly,unless the temp should be lower than 170 on exit,i would try putting a bottle of that super coolant [i used hyperlube] i also replaced my original fans with aftermarket ones [they almost sound like a turbo when on] i put the biggest i could fit,think they were 10in and just some brand that local auto stores carry,one of mine stopped working so first i would put ac on and look with flashlight that they're working,and of course check that viscous fan is good

 

Interesting... I have noticed mine building heat while sitting with the AC on (25 mins at idle brought her up to 215), granted ambient temps have been in the 90-100* range here lately

I'm running a new eBay radiator that keeps her at 184* on the street, I figured it was just the summer heat

Fan clutch seems OK and so do the AUX fans but it does make me nervous, especially when things get slow on the trail.

 

what are you guys using to measure temp,i tried hooking up an obd11 and leave it but it only says system ok,do you use a ultra gauge? am i doing something wrong with obd?

 

Mine does the same thing with AC on. Runs fine temps then hit a traffic light and I can watch that gauge start creeping. Light turns green I go and seconds later it starts rapidly dropping. Have yet to determine the cause. Almost don't care anymore and just only run AC on highway. Sucks, but, more important vehicle repair priorities unfortunately...

 

OBDII wifi dongle and OBD Fusion app for iphone. Realtime data.

 

Most guys seem to go with the Ultragauge, I run the Scangauge E in both my trucks because it fits perfectly in either the coin holder or ash tray locations;

 

fan clutch is my vote (if you know you dont have a leak)
they can seem fine by hand but should be replaced with the water pump as I understand they are usually dead at 50 to 100k

 

fan clutch is 1 yr old (OEM because the autozone cheapie was just too aggressive and loud) and judging by the sound the "roar", it is working properly.

 

Unrelated self-serving dumb question, when you turn your Ac on, do both fans spin up? I am just noticing one turning on