98 XJ- the jeep still has ac that works but everytime heat/air is on, the efan cycles on and off, on and off, on and off. Any ideas? Just kind of annoying and its drawing the alternator down pretty bad...

 

With AC selected the E fan will cycle on and off. With Heat selected it shouldn't be running unless your coolant temperature is too high.

How is it drawing the alternator down? Are you seeing the engine RPM sag when the fan is running?

 

Yup, it does when is heat is on also. That's my confusion. I'm wondering if its something with the thermostat? Temp is always perfect, think it tops out at 195.

Yeah it starts to bog down and voltage drops to almost 9 then back up to 12. We've been having a slight starting issue and will have to pump the gas to get it to start up...

 

If you have it on defrost that will kick on your AC compressor and possibly the E-fan too.

 

Cool, thanks. I'll have to try it on others and see of it doesn't do it. I almost always have it on defrost...

 

The IAC should control engine RPM at idle, if within its control range.

It looks like you may have battery or alternator problems.

You should drive your Heep up to Advance or O'reilly auto parts and see if they'll do a battery capacity test with the battery installed. They usually do it for free. If the battery is okay, you may want to remove the alternator and take it to them for a bench check.

 

Could the temp senor on tge thermostat housing have anything to do with the e fan staying on constantly causing the heat inside not being great?

 

ELECTRIC RADIATOR FAN RUNS
ALL OF THE TIME (2.5L/4.0L
MODELS EQUIPPED WITH A/C
AND 4.0L MODELS EQUIPPED
WITH MAX COOLING)
1. Fan relay, powertrain control
module (PCM) or coolant
temperature sensor defective.

 

I thought you said the fan cycles on and off, on and off, on and off.

The PCM uses the same voltage output from the ECT sensor to run the coolant temp gauge as it does to trigger the fan when the coolant temp reaches a preset value.

If you re seeing 195* F on the temp gauge there's a chance that's what the PCM sees as far as the trip point for the fan, approximately 218*F.

The electric radiator fan serves two purposes: To assist in cooling down the engine if the coolant temp gets above 218*F and to draw air accross the AC condenser when AC is selected.

If you do have defrost selected on your AC/Heat control panel mode selector (#5 or #6 in pic below), AC is being requested and the compressor will engage. If you have the Temp Selector on the AC/Heat control panel selected to a midscale (Blue/Red) setting, you will get the 'heat not being so great' because the blend-air door is allowing cold air from the AC evaporator coil to mix with heat from the heater core.

Try moving the Mode Selector to the panel outlets (#7 or #8 in pic below) and turn the Temp Selector to full heat (Red range) and see if the fan still runs on-off. If it does, there's a fault in the AC circuit or in the ECT Sensor circuit.

To isolate the AC system altogether, remove the electrical connector from the low pressure cyling switch on top of the AC Accumulator. This will kill the AC system and the fan should not run at all - if the fault is in the AC circuit. If the fan still kick on and off then it can be assumed you have a ECT Sensor fault or a fault in the fan control circuit.

 

Cycles on and off. Oil pressure is at 10lbs this morning at idle

 

This is confusing.

ON/Off cycling is normal, like CC said. If it stays on, then either it does this because your coolant temp is high/ECT sensor is giving the wrong reading causing the PCM to think your running hot, or (as in my case) e.g. the relay is faulty.
My e-fan also cycles when selected position #5 (which I only found out now, since I never use is here in Queensland, Australia)

Side note: CC, is there anything that you DON'T have a pic of?! lol