slotcarboss

I have a 99 corvette that runs 230 degrees in street driving and 195 on the freeway.The cooling fans never come on.I jumpered the relay and the fans came on.I pulled the relays and checked them with my meter.Contacts open and close when I put 12 volts to the relays.Analog and digital temp work.Fans work,relays work,temp sending unit works.What else is there?

slotcarboss

thank you.I already have that drawing.like I said the fuses and relays are good.The only other item in the drawing is the PCM.Do I need a new PCM?

pewter99

lionelhutz

I doubt both high and low speed fan drivers in the PCM failed at the same time so you likely missed something in your wiring checks.

My guess would be that the low speed circuit has some issue since the high speed doesn't kick on until 236*F. Check relay 44 again and make sure the N/C contact is good.

Evil-Twin

The fans do not run above 35 mph. If you are seeing those temps on the highway you have other problems. Bad stat, clogged AC condenser, or a blocked radiator or both. Radiator and coolant contaminated over time and needs to be flushed and replaced.

Alvin@PCMofNC

On PCM check to see if red 33 and blue 42 go to ground when you think the fans should be on. The easiest way to get both to come on in short order is to turn on the A/C. Especially if the fans are not working. Also has the car been tuned? If not the stock fan turn on points are quite high.

slotcarboss

Well that's another thing the ac doesn't work.When I press the ac button it blinks 3 times and goes out.

racebum

have you cleaned the condenser and replaced the radiator? ac delco 20889 is something like $190 shipped on amazon and imo should be done on any c4 or c5 over 10 years old or 50k miles {100k miles max} with them OEM radiator. these cars are literal vacuum cleaners and you will typically have a sand castle when you clean out the condenser. at a bare minimum clean them both with 100+ psi and the air gun and or a garden hose with a pressure sprayer tip.


even with the fans working you will run 230+ in town with a clogged condenser and radiator.

this is a shopping list of your cooling system parts minus fans and relays

Ac delco 20889 radiator $188.16
Ac delco water pump 251-744 $177.61
Ac delco water pump inlet w/ stat 15-11057 $29.30
Ac delco 18021L hose $27.52
Ac delco 24388L hose $25.35
Ac delco 24458L hose $14.59
GM hose 10229491 $24

SacCityCorvette

If you sit and idle what does the temp go up to. The fans should kick on around 230 degrees.

jpatrick636

Lurking

LoneStarFRC

In a two year old thread?