87 GN air conditioning issue

[theman1990]

You should have the FAST program to work on this car with, even if there's no AC issue.
No reason your LT, assuming it's not DOS based, can't load that program.
Before you do that, determine if the ac relay is even wired into the FAST.
From what I gather, the stock ecm is still in use and the FAST is on the engine. Y/N?

Incorrect (b/c I'm new to standalone stuff...) The XFI REPLACES the factory ECU completely. I didn't know this until I pulled the kick panel to get the ECU model and found the XFI. The few electronic tune stuff I have ever used still utilized factory ECU so I assumed this did, too. My mistake The XFI uses a serial port cable which I haven't used on a laptop in a decade... I did order a converter cable so we'll see... The relay is DEFINITELY being controlled by the green/yellow input wire from the ECU and all signs point to a likely thermostatically controlled setting with the numbers probably set to disable A/C clutch at 180ish hence it turning on/off at very consistent periods at idle... It engages, water temp increases a few degrees due to load, it gets turned back off, water cools, repeat.

 

[Chuck Leeper]

Incorrect (b/c I'm new to standalone stuff...) The XFI REPLACES the factory ECU completely. I didn't know this until I pulled the kick panel to get the ECU model and found the XFI. The few electronic tune stuff I have ever used still utilized factory ECU so I assumed this did, too.

A totally new ballgame....
G/L with the investigation

 

[theman1990]

A totally new ballgame....
G/L with the investigation

Ya, the guy above as well as tech at FAST agree that the "A/C cutout temp control" is set too low... It's to protect against overheating sooooo fingers crossed!

 

[John Larkin]

If you don't have a front mount, you will be fine. Coolant will probably get to 210 while the a/c is on because you are introducing alot of heat in front of the radiator but it will cycle. Just don't flip your wig when it happens, I did and then found out it is normal.

 

[theman1990]

Problem solved! The FAST XFI was set to cut the AC off above 210 degrees! Now I have to figure out why the engine at idle long enough gets up to 240° lol

 

[XracerX]

Glad you found the FAST setting causing the issue. Problem is that it shouldn't get that hot, but could.
Could possibly be a bad thermostat.
I'll guess and say its prolly got a 195* thermostat.
Most of us replace it with a 160 degree. You should consider the 160* thermostat since your in Florida.
Could also be air in the cooling system. or low coolant. or a clogged radiator is worst case scenario.
When it gets up to 240* how far down does it drop when the thermostat opens? If you have the ability to read the coolant temp this would give you some idea of what thermostat is in it.

 

[XracerX]

"The suspense is killing me. I wonder how long it will last." Willy Wonka

Hi Chuck !

 

[theman1990]

I think it might be that the PO retained the stock fan... The car is putting out 380hp at the wheels w/ a front mount intercooler so I suspect it's just heat soaked. I ordered the double spal fan to go with the big 3 row aluminum radiator.

 

[Chuck Leeper]

"The suspense is killing me. I wonder how long it will last." Willy Wonka

Hi Chuck !

Hi Joe!