The problem with your assumptions in this scenario is that even if you [complete] a circuit, the A/C still isn't simulating normal function. You have one or maybe even two pressure switches and without a wiring diagram, Lord only knows what else.
Everything else should think the compressor circuit is completed. What leads you to believe otherwise? The difference between positive and negative across the clutch coil induces the E-M field, but that field doesn't energize anything else or send a signal back. You can see that here:
That, of course, is for a fox, but hey... that's what we know, here.
That, of course, is for a fox, but hey... that's what we know, here.
You can simulate electrically the A/C being "on" all you want, but it will never simulate the load on the system, either from the power required to spin the compressor or the flow of refrigerant through the system.
If possible, I would hook up a set of gauges to the A/C system and tape it to the windshield and drive the car. The pressures may be normal at idle, but when driving down the road you may have higher than normal pressures building up in the system creating extra load.
The Grand Marquis also probably has ambient air temp sensors in the duct-work and in front of the car to measure outside air temp.
Did you mention if this vehicle has Auto A/C or Manual A/C? The electrical system is different for each system.
If possible, I would hook up a set of gauges to the A/C system and tape it to the windshield and drive the car. The pressures may be normal at idle, but when driving down the road you may have higher than normal pressures building up in the system creating extra load.
The Grand Marquis also probably has ambient air temp sensors in the duct-work and in front of the car to measure outside air temp.
Did you mention if this vehicle has Auto A/C or Manual A/C? The electrical system is different for each system.
Can’t you just jump out the low pressure switch and unplug the compressor?
If you want, measure the resistance of the coil for the ac clutch and install an equal resistor across the two wires to the compressor
I can only relate to what my ‘00 GT 4.6 does, and the ac system is not that smart. Doesn’t really know if the compressor engages or not.
How good is your OBD2 scanner? Can it do live data?
Go to pid 106 (I think) which is “total misfires” it may not be that pid so search around. Display this and go for a drive. Turn the ac on and se if this is counting misfires. Sometimes it will count them but not enough to throw the CEL.
There’s other data you should look at as well when the issue occurs. Misfires, short and long term fuel trims, as well as o2 data. I’d go for a ride, get the situation happening and hit record and then go back and see if anything looks off
Go to pid 106 (I think) which is “total misfires” it may not be that pid so search around. Display this and go for a drive. Turn the ac on and se if this is counting misfires. Sometimes it will count them but not enough to throw the CEL.
There’s other data you should look at as well when the issue occurs. Misfires, short and long term fuel trims, as well as o2 data. I’d go for a ride, get the situation happening and hit record and then go back and see if anything looks off
Ok, not sure if this helps, but I found a webpage with the AC wiring diagram for your car. I hope it helps:
But to answer your question you posted about my previous post, I was suspecting the PCM might have a fault that upon receiving the signal to engage the AC system, was sending bad/wrong impulses to any vehicle feature creating your headache. It appears from the diagram, the PCM isn’t so involved in that system, although, lots of stuff is. Good luck.
Air Conditioning — Mercury Grand Marquis LS 1998 Wiring Diagram
Air Conditioning wiring diagram for Mercury Grand Marquis LS 1998. Component locations, pin connections, and complete circuit paths.
But to answer your question you posted about my previous post, I was suspecting the PCM might have a fault that upon receiving the signal to engage the AC system, was sending bad/wrong impulses to any vehicle feature creating your headache. It appears from the diagram, the PCM isn’t so involved in that system, although, lots of stuff is. Good luck.
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So I am building a '70 F100 with a 2006 CV front suspension so I have a login to crownvic.net and mercurymarauder.net so I did some search and I think this answer is in this thread:
Hope it helps but I am not 100% sure as I have never owned one personally just cut one up for the parts.
Hope it helps but I am not 100% sure as I have never owned one personally just cut one up for the parts.
"My 98 p71 also does this. Im guessing the extra load causes the tcc to unlock. When I datalog thats exactly what its doing, unlocking when the compressor initially kicks on then reapplies. Do you have any problems where it will almost die when coming to a stop then it revs and the car lurches forward?"
Might be what yours is doing. TCC = torque converter clutch solenoid.
For the most part the guys on crownvic.net are pretty helpful but the guys over the the Marauder site are way more technical.
Might be what yours is doing. TCC = torque converter clutch solenoid.
For the most part the guys on crownvic.net are pretty helpful but the guys over the the Marauder site are way more technical.
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