Hello I have read so many similar situations but I haven’t found my exact situation.

I have only put a couple hundred miles on this project since getting it back together.

first trip last Friday morning to work 20 miles each way with light in and around miles.

no overheating. But I never heard a fan.

got home and was looking at relays and decided to check the Ac compressor mini relay. It was bad so I swapped it.

from then on almost immediate 220° and above. 240° at speed and even close to redline on coolant.
fan would audibly run for minute plus

tonight I removed the relay and let it idle in neutral for 30 minutes 217° and fan ran for less than 5 seconds

what is wrong with my compressor to cause this increase in temp. Clutch? Whole compressor?
any help would be appreciated

 

So are you having issues with your radiator cooling fan or your AC compressor ??…relay has nothing to do with the cooling fan…is your cooling fan running at low speed when you start the car with the AC turned on ??…you will need an inspection mirror and light to check…the cooling fan should be running at high speed (90% duty cycle) at 225 degrees ECT and higher…if not check your cooling fan connector….may be melted.

 

 

I don’t think the overheating is fan related. Even though I don’t have a good understanding of the variable speed fan. I don’t think it’s the problem.

I think when the ac compressor clutch engaged it puts unnecessary stress on the engine causing it to heat up way too quick. When I pull the ac relay this doesn’t happen.

has anyone had this?

 

I have never seen this but in theory I guess it can happen…is the AC cooling the car sufficiently??…compressor making any noise ??…it would probably help putting a manifold set on the system to check your high and low side…with a factory level scan tool you can check the high side pressure which should be around 200 psi on an 80 degree day…when you turn the AC on and off does the RPM drop significantly ??..I would take the car to an AC shop for a diagnosis…AC work is not a DIY type of job.

 

As stated, when AC is on(compressor clutch engaged), even with motor bone cold, raditor fan should be running and stay running when the car is sitting with motor running..
The reason for this, the ac condenser/heat exchange coil sits in front of the radiator, and the fan is needed to pull air through it, so it can dissipate the heat.

So start car with hood open, and go listen to make sure Radiator fan is spinning, and stays spinning as car is sitting.motor running with ac on..

If yes on radiator fan coming on and staying on as car is sitting with motor on, then second guess is that the condenser, that sits in from the radiator is clogged up. Hence radiator can pull air from around the condenser when ac is not on, but with A/C on and its condenser clogged, condenser is going to be very hot with it clogged in any way, and this is going to cause the radiator to be even hotter as well.

So start by getting under the noise of the car to look up in front of the lower air dam, to look for plastic bags, or leafs that are blocking the front AC condenser coils to be begin with.


If such is found, or not found but still have problems, then may be debris that are clogging up the vanes of the condenser (and maybe radiator as well) that will be needed to be back flushed out forward instead.

For air and water wands to forward flush radiator and condenser to clean the debris out of them.

 

If problem is radiator fan comes on, but only for a second and shuts back off, then would be checking the raditor fan connectors (one side of raditor, and other at PWM, as well as ground wire to chassis off PWM connector) for heat melting/corrosion problems.

If all that checks fine and not a problem with Radiator or PWM controller,, then would be checking to see if aftermarket tune in play, to see if radiator fan for A/C kick off/on pressures has been screwed with from say a bad retune flash (system/AC/ ran disable conditions, and system/ fan/desired % verses Ac pressure).


Also to note, ac has to be pressurized correctly to begin with so system/ fan/desired % verses Ac pressure are correct , pressure switch 19 needs to be working correctly for same reason, condenser in line Freon accumulator/ filter 11 needs to not be clogged to cause higher pressure on high side.


Here is a download for A/C pressure charts,
https://download937.mediafire.com/gq...ure+charts.pdf

 

I believe the fan works in all scenarios. I believe the radiator and condenser is clean. Vette stayed below 217 while idling for 30 minutes parked wit ac on.

last night I took it for a 6 mile round trip drive and within the first mile temp gauge jumped to 245 and I received a “check coolant level” message.

their may be a chance I have a air bubble so tonight I’ll take the cap off let it idle turn the heat on and see if I can figure that out

 

Just taking the cap off won't get the air out.

Put suction on that little hose going into the side of the reservoir.

 

Just like a brake bleeder?

 

Was the coolant changed recently ??...if so the vacuum bleeding method is the preferred method...I just did mine last month with no issues...you can get a kit on Amazon for less than $100.00.

 

A Plews suction gun (really a big syringe) on the small upper overflow tank line and it will suck the fluid though the system. The AC when activated always needs the fan on to have air going through the condenser even if you just started up and a cold engine. If not the condenser heats up quickly and you will get a spike in the line pressure which will shut AC and or do other bad things like blow a hose. Get fluid level fixed first as there is a host of issues that come up with that situation.

 

Thanks for your posts that display the proper electrical shematics for a lot of problems. Most people don't have a service manual.

Tom

 

Anyone can get these OEM and these Mitchell color schematics and all service info from Alldata DIY for $19.99 a month !!..you don’t need these multi volume books.

 

Good news is I bled the line with a syringe and it seems to stay below 216 on a pretty aggressive
fan works as it should.
I had to add a little antifreeze to hit the cold level in the radiator reservoir.

bad news I started charging the AC and the rubber line has a hole in it!🤦‍♂️