Radiator Fans - 99 Venture

I am troubleshooting my temperature fluctuations. I replaced my water pump which was leaking through the weep hole. Actually I was surprised that it could fling as much coolant as it was flinging. I thought the LIM gasket again.

I am also driving around with a code reader that gives me real time temperature readings. It now seems to hover around 199 F but sometimes goes as high as 204 F but only for a few seconds.

I am still burping my cooling system of air. I let it idle today and the radiator fans did not seem to come on. I checked the temperature and it was a steady 199 F. The ambient temperature was about 32 F to 35 F or so. I suppose the radiator is capable of releasing the heat at idle in the cool ambient air without needing the fans but I'm not sure.

I checked the 2 30 amp fuses and they seem good. I looked at the relays but did not pull them to test but I will soon. I assume they pull out with a bit of force.

For some reason my questions were truncated from my original post. So here they are:


1) Does the PCM use a separate temperature sensor to control the cooling fans? or is it the same one as the temperature gauge?
2) What temperature do the cooling fans trigger at?
3) do they come on as a pair? or one at a time?

The sensor near the water neck has a circuit for the dash guage and a switch circuit for the fans, one of the fans is keyed off the AC system IIRC. My fans trigger at like 230* (I was worried but my uncled wasnt (GM Mechanic)).

Hi DRW1000,

I have a pretty good amount of detail about the 2001 cooling system & fans (see page here (http://www.my-chevy-venture.com/engine-cooling-system.html)). I believe the 1999 is the same, but I can do a little checking on that.

If your scan tool says less than about 220 F, then you should be OK. You may also be able to turn on the heater, to the Defrost setting to see if the fans will kick on. Defrost turns on the AC compressor and cooling fans, most of the time. I don't know if that would happen at 32 F outside air temperature though.

Let us know what you find out.

Take Care,

Hi GregA,
Excellent information on your site. If I understand the conditions for the fans to come on it seems that the A/C has to be in working order. I hope this isn't the case because I lost my refridgerant a year or 2 ago. There is a huge hole I believe in the lines going to the rear evapourator. I never bothered to fix it as this is a winter beater.

I also see that the temperature needs to be a lot higher in any event to trigger them to come on.

If it is mild enough over the weekend i will bypass one of the relays to see if the fans spin.



Hi Lesterl,
Thanks for the info. It seems consistant with what GregA was saying as well. BTW how do you know your temperature? My gauge only gives the extremes. I had to use an external Code reader to get the actual temperatures.