Electric fan/AC on, what controls it

tbonz

tbonz

Registered User
My compressor cr@pped out last week, so my brother installed a new compressor, accumulator today and converted my system. Only thing, his friend who charged the system said the fan should go on when the ac is on no matter what... is that true? My fan doesn't go on when the ac is turned on. What controls the electric fan, what should we troubleshoot?



Thanks for any info!



Todd
 
The fan is controlled only by the EEC. The AC system has to "tell" the EEC to turn on the fan. The fan will not turn on unless there is enough refrigerant in the system to trigger the compressor. This can be simulated by short circuiting the pressure switch on the accumulator/dryer.
 
Yes, the fan must run to pull the heat out of the condenser; otherwise no cooling and possible overpressure. The EEC shuts the fan off when cruising at 45 or higher since there's enough air flow. Could be a bad IRCM.

I worked around it by wiring a diode inbetween the compressor "on" wire and the low speed fan "on" wire so that when the compressor is engaged the fan turns... but thats not the right fix for the problem.
 
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XR7 Dave said:
The fan is controlled only by the EEC. The AC system has to "tell" the EEC to turn on the fan. The fan will not turn on unless there is enough refrigerant in the system to trigger the compressor. This can be simulated by short circuiting the pressure switch on the accumulator/dryer.
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Yes, what he said.
 
TbirdSCFan said:
Yes, the fan must run to pull the heat out of the condenser; otherwise no cooling and possible overpressure. The EEC shuts the fan off when cruising at 45 or higher since there's enough air flow. Could be a bad IRCM.
Click to expand...

If the IRCM is bad then the fan won't run on low speed at all. Do a KOEO test to verify EEC control of both fan speeds. If the AC is charged and the compressor runs, the fan will turn on (assuming it works).

As for the mph related logic, the fan only shuts off at 40mph IF the only reason it was on in the first place was due to the AC. If engine temp demands the fan on, it will come (and stay on) on regardless of speed until temperature drops below the commanded "off" temp.
 
XR7 Dave said:
If the IRCM is bad then the fan won't run on low speed at all. Do a KOEO test to verify EEC control of both fan speeds. If the AC is charged and the compressor runs, the fan will turn on (assuming it works).
Click to expand...
Since I've wired in fan control switches in all 3 of my birds, I don't pay that much attention to the fan operation on my my 5spd. I'll try it and see.

XR7 Dave said:
fan only shuts off at 40mph IF the only reason it was on in the first place was due to the AC. If engine temp demands the fan on, it will come (and stay on) on regardless of speed until temperature drops below the commanded "off" temp.
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Yup. I wired in an override switch for both speeds and a fan-power-applied led on my dash right under the auto-lamp switch. This is how I know its 45 for A/C and also how I know if it turns on at the right time.
 
How hard is it to convert it to the new system? Is there a kit we can buy? How about a web page with instructions.
 
sccrewzer said:
How hard is it to convert it to the new system? Is there a kit we can buy? How about a web page with instructions.
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Not hard, but you need to have your R12 recovered by a professional facility. Then you can replace the accumulator / dryer with a new one, and replace the fittings with the R134 ones.

Technically, you dont HAVE to convert, you could keep it R12, but the refrigerant is expensive.

- Dan
 
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