Running Hot and No A/C - Chevrolet Problem
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Customer Complaint: This 2014 Chevrolet Suburban with a 5.3 liter engine came to the shop for a running rough issue along with low idle and stalling at stoplights. While it was at the shop being diagnosed for this issue, we noticed it was running hot and the air conditioning (A/C) would not work well. We talked to the customer and asked if they would like us to chase after this issue along with the original issue. The customer said yes and I started to dive into it.
First Thoughts: This vehicle is a little strange. It would not overheat and the A/C would work fine going down the road, but when idling for long periods, it would run hot and the A/C would not cool well. The A/C was still a little cool, but not the temperature it was supposed to be.
There can be many issues that can cause a running hot issue and an A/C issue. But the issues with this vehicle actually have something in common.
First, we will talk about the two different issues and some common causes.
Common causes to a running hot issue:
Low coolant.
Bad water pump.
Bad thermostat.
Bad cooling fan.
Common causes to an A/C not cold enough issue.
Low freon.
Dirty/ Clogged A/C condensor.
Dirty/ Clogged A/C evaporator core.
Bad cooling fan.
All of the issues above were possibilities to these issues, but there was one thing I thought was interesting on this vehicle.
Diagnostics: I noticed when the vehicle was idling for a while, the A/C was running, and before it was starting to overheat, the left cooling fan was the only fan running. The left fan was running full blast, but the right fan was not on. I thought this was strange because when a vehicle is hot and has the A/C on, the fans will usually be on at the same time.
I had to let the vehicle cool down because it was getting hot and decided to check the codes with the scan tool.
No codes were in any modules.
I decided to look up the description and operation of these cooling fans. I had a feeling that they were supposed to be on at the same time and only one of them being on was my issue.
After reading about these cooling fans and how they operate, I found that the cooling fans have separate relays that control the low and high-speed operation.
Note: I use Alldata for all of my service information. Alldata has a vast amount of information like descriptions and operations of different systems on a vehicle, step-by-step repair procedures, and wiring diagrams.
After looking at a wiring diagram, I found which wire was the power feed for the right-side cooling fan.
I started the vehicle and with my Power Probe 3, I was able to see the voltage was not correct. It should have battery voltage on that wire going into the fan, but it only had 7 volts.
The fan did not have enough voltage to turn on. But why? My thoughts were there must be some corrosion causing resistance or a wire that is partially broken.
I decided to look at the fuse for that specific cooling fan. I didn’t notice any corrosion, but I did notice that it was unusually hot. I felt the relay for this specific fan and it was unusually hot too.
What I found next was shocking.
Notice the color of the relay.
Burned relay
This cooling fan relay got HOT!
It melted the fuse box!
Well, I found my resistance.
What caused this to happen? The right fan shorted and caused this to happen.
After replacing the cooling fan assembly and fuse box, the vehicle did not run hot and the A/C was nice and cold.
Fixed!
A lot of mechanics forget about the cooling fans when diagnosing these problems. The cooling fan is an important component in keeping the vehicle cool and keeping the A/C cool. Always make sure the cooling fans are operating correctly when diagnosing an overheating issue and/or an A/C issue.
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