: radiator fans?



hankk17
04-28-04, 01:36 PM
hey all. I replaced my radiator some weeks back on my 99 eldorado. I filled the radiator with dexcool and distilled water and massaged the top hose until the system was purged of all air.

Since then I've noticed a few times that the overflow tank has been dripping a bit - which I figure is normal as the system is balancing itself out.

My real question though is this - yesterday after a long hard drive down Rte 495 I pulled into my driveway and popped the hood to check on things. I noticed that only 1 of my fans on the radiator was spinning.. and the other was sort of trying to spin, but I could stop it with my finger.

I know for a fact that after I did the radiator replacement that they were both running at the same time... but now they're not.

Do the fans run independantly of one another? Or should they both engage when the computer tells them to?

hankk17
04-29-04, 05:34 PM
anyone? anyone? anyone?


bueller..?

RLLOVETT
04-29-04, 05:41 PM
I'm no Bbob but I think they come on together...

LCLCLC
04-29-04, 11:19 PM
Looking at a 97 manual... There are three relays that control the fans. They are all just below and between the two fans. If you recently had the radiator out, I would think you would have 'disturbed' these relays, wiring, and connectors. First thing I would do is reseat all connectors, and then look for pinched or broken wiring, etc.

Looking at the wiring diagram, and I'm not the greatest at electronics (plus, I don't know how the PCM actually controls the relays), it looks like both fans are to run at once.

But, strange to me at least, there are two circuits (each controlled through grounding the relays by the PCM) - a 'low speed' and a 'high speed' (this is why 3 relays are needed). And stranger, it gets the 'low speed' by running the power in SERIES through the two fans. This will reduce the voltage/power to both the fans, making them run slow.

The second 'high speed' circuit switches the relays so each fan has the full 12volt available to each, in parallel, which would allow them to run at full speed.

As I said, these are both controlled through the PCM computer.

Does anyone else have this diagram? Is this how it really works? Is something like this a standard design in autos to get 2 speeds out of fans?

BeelzeBob
04-30-04, 12:39 PM
I believe both fans should run together in either LO or HIGH speed. The relays configure the fans in a series/parallel arrangement to control the speeds. If one isn't running I would start checking connections....

Lawrence
04-30-04, 12:40 PM
hey all. I replaced my radiator some weeks back on my 99 eldorado. I filled the radiator with dexcool and distilled water and massaged the top hose until the system was purged of all air.

Since then I've noticed a few times that the overflow tank has been dripping a bit - which I figure is normal as the system is balancing itself out.

My real question though is this - yesterday after a long hard drive down Rte 495 I pulled into my driveway and popped the hood to check on things. I noticed that only 1 of my fans on the radiator was spinning.. and the other was sort of trying to spin, but I could stop it with my finger.

I know for a fact that after I did the radiator replacement that they were both running at the same time... but now they're not.

Do the fans run independantly of one another? Or should they both engage when the computer tells them to?

The fans do run independantly and have 2 speeds. Turn on the AC. Both should run full speed. If they do I would say you are OK.