I was checking my refrigerant charge yesterday and noticed the head pressure would pop up and back down.

I noticed the passenger side fan would run then slow down and stop, then start running again.

Could'nt see driver's side fan because the ABS module in the way.

I'm thinking that motor shouldn't be cycling like that, but read the fans only come on with A/C at 185.

Anyways the A/C has poor performance and I recently put in some stop leak, but had many other projects going and was going to add more refrigerant when I found the fan doing this.

Is it supposed to go off and on, on C5 Corvette?

C5 Cooling Fans Operation

The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

Yes I had it in the garage, was ready to add more refrigerant when I noticed the head pressure go up and down, So I held off adding any.

I am a HVAC and a commercial refrigeration technician, but never any professional work on cars, on about 99% of home, office, commercial building A/C or refrigeration units, if the compressor is running, the condenser fan motor is running also, except for defrost modes.

Also most other cars I've helped friends and family with, the radiator/condenser fan is running with the A/C on, but most likely shuts off at a certain speed like the C5.

I'm wondering why they designed these cars to have the compressor running but no fans to pull air across the condenser to help shed the heat out of the refrigerant, maybe to help car get up to temperature faster for emissions purposes?

I'll trouble shoot the fans electrical, but with out A/C the fans run perfect, car holds 198 most times, and I have heard fans kick on at 226, and off at 219 sitting in a long drive thru.

I love having good cold A/C, Phoenix area is awful without A/C or poor performing A/C.

I'm trying to give a update, before I forget what I saw.

Yesterday I took another shot at it and charged it up, but before adding any refrigerant I just observed for a little while, the passenger side fan was coming on and off while the DIC was below 185.

I tried looking again to see if driver's side fan was running but again it's hard to tell with that abs module in the way.

Probably need to get the car on ramps and look underneath, I will report what I find when I do that.

After charging it up, I noticed the passenger side fan started running in high speed.

Probably time to clean the area between condenser and radiator while seeing what both fans are doing, never have tried it.

Good news seems my refrigerant leak is gone with the stop leak I added, it was losing refrigerant pretty fast, in September 2017 I charged car up and it was cooling, the next day took car for drive and a/c light was flashing and no compressor running.

I put gauges on and it wasn't empty, but low enough to keep compressor from running with pressure switch.

That fan cycling on and off in low speed below 185 F, could it cycle on low speed when head pressure climbs, and back off when it goes back down, by design?