2004 F350 6.0, 180,000 miles

The original ac compressor started working sporadically. It would cool, then stop cooling, then start again. It had good pressures & freon. I thought it might be the air gap on the clutch or a bad pressure switch, but before I could check, the compressor locked up necessitating replacement.

The compressor has been replaced, and works great, but if you let it sit at idle for a few minutes, the high side pressure will climb past 275. Putting a fan in front of the radiator would instantly drop the pressure down to 225. It appears that the excessive high pressures grenaded the compressor.

A code scanner was attached, and if the truck is started cold, the rpm's for the cooling fan show to be around 350rpm, but within 5 minutes drop to 100rpm. I was told the rpm's should be around 700rpm. You can put your hand on the blade while idling and easily stop it from turning.

I have a spare 2005 engine with 56,000 miles I bought complete with a cooling fan. I replaced my original fan with this one and it has the same rpms. I replaced the sensor switch on the thermostat, but still no change.

How can I test the cooling fan to see if it is working properly?

How can I diagnose to make sure the computer is sending the right signals to the fan to increase the rpm's?

What other sensors might be at fault?

Does the computer need to be re-flashed?

A new fan is around $350.00, and I don't want to buy a new one if it is not the cause of the problem.

Anyone know what might be the problem?

Thanks in advance....

 

Sounds like you need a new Fan clutch

I will look the values up for it

Is your EGR Valve plugged in

 

EGR is not plugged in, by suggestion of this site.

Will that cause the fan to not operate properly? If so, wouldn't everyone who unplugged their EGR experience the same problem?

Do you think that two different fans could be bad?

 

There are lots of varibles that controll the Fan
ECT
A/C
Ambeint Temp
Vehicle Speed
and there maybe some that I missed

and heres the value
FANSS 0 533 488 0 - 4000 RPM Fan Speed
KOEO= 0rpm
so 533 Fan rpms at Idel
and 488 Fan rpms at 2500 Engine rpm

When I start my truck
ECT under 100*
Ambeint Temp 94* or Less
My fan RPMs 400-550 RPMs

The PCM uses lots of things to determine Fan speed

Make shure EGR valve pluged in
Check the wire harness at the fan shroud known Chaffe spot

Do you have a Scan Gauge theres a X-code to watch the fan

 

It has been determined that aLL years need the EGR valve plugged in for fan operation from some of the FORD Techs and a few others
IIRC everyone that had the EGR Valve unplugged didnt have the All the Fan steps it is all or nothing

this could very well be your problem

Even those who do an EGR deleate need to plug the valve in so the fan works

Plug the EGR Valve back in for shure

And an answer to your ??? YES everyone that has the EGR Valve unplugged has an issue with the fan operation wheather they know it or not

and odds of 2 fans bad are slim

 

to test the fan you need a scan tool that can active command pids.
command fanvar# to 100% then moniter fanss and rpm.
with rpm at 2500 fanss should be 2800+

 

I don't believe 275 is an excessive high side pressure. Also, there is a high pressure cutoff switch that will stop the compressor if the pressure gets too high. I can't find what that value is, though. There is even a high pressure relief valve to protect the compressor. I don't think high pressure could have damaged your compressor, unless all of these failed.

It would still be worthwhile to test the fan operation as Cheezit describes. However I can say my fan does not come on for A/C unless it's really hot outside.

 

OK, I found it. The high pressure switch opens between 435 to 475 PSI. The relief valve opens between 550-600 PSI. This tells me that Ford specs the compressor to be good at pressure up to those values.

 

Plug your EGR in...... it was bad advice to unplug it.

 

EGR valve is plugged in.

Same problem...any other suggestions?

If the computer is telling the fan to turn a certain speed and it is not, would there be a code thrown or some sort of error message?

If I took it into a Ford dealer, would they be able to diagnose the problem, or just try to sell me a new fan?

Any particular dealership in Houston, Texas to consider?

Just a note: I unplugged the valve from advice garnered here. There was a whole big thread a few years ago about how to do it, and why it should be disconnected.

 

I know I probably read the same thread about unplugging it. But after some reasearch by many folks on here it was determined that EGR valve needs to be plugged in for fan operation. Heck I have an Full EGR deleate but I still have the egr valve plugged in just for fan operation. Just the nature of the beast..

The Ford Dealer should be able to diagnos it for you
Have you already tried to put a new Fan clutch in???

Have you looked at the wire harness at the fan shroud for wire chaffe??
are all the pins good on harness none broke or bent

 

So far I haven't seen anything that would indicate that you actually have a problem.

However, the dealer should be able to verify the operation of the fan by activating it to 100% and watching the fan speed.

 

Does it chaffe on the wiring harness of the truck to the plug where the fan connects, or from the plug/wiring attached to the fan?

 

right here is one spot that I know of at the fan shroud