QuestionI have a 889 grand Marquis and the A/AC gave out. The compressor will not engage even with a jumper wire across the terminal @ the compressor. Because of that I cannot accurately check the pressures with gages. However, with hoses connected the low pressure side reads almost normal psi of 30-50. The high side reads nothing. I'm leaning towards the orifice tube being restricted, clogged or otherwise in need of replacement.
Also, I'm not sure if related but the blower motor only works on high and when placed on it draws down the lights something terrible.
I read past post and I will check the blower resistor (if I can find it).
I started off by replacing the low pressure switch and it didn't help my situation other than now having a new low psi switch.
Thanks in advance!
Johnny
AnswerJohnny,
First, I am going on the assumption that you have the Grand Marquis GS 5.0L with the manual A/C versus the automatic A/C. If you have the automatic, the checks will be slightly, but not much different.
You said you jumped the terminals at the compressor? The terminals that you need to jump are the ones in the low pressure switch plug. With the Key in the run position, and the a/c switch on, if you jump the low pressure switch plug, that should allow you to hear the compressor clutch engage. If you are reading 30-50 psig with the compressor off, that tells me that your system is very low on refrigerant. Dependant upon where your low pressure switch is set to open the contacts at, there may not be enough pressure in the lines to close the contacts. Try this first.
If still nothing, check your light green/purple wire for 12 Volts. If you have voltage at this point, The next stop for voltage is the Wide Open throttle cutout relay. You should have voltage on the Black/yellow wire coming out of this. From there it travels to the clutch itself.
Going back to the pressure switch... if you do not read voltage on the lt. green/purple wire then the problem lies in the control switch. (Assuming you have already checked your fuses)If you havent checked them then check these before everything else.
Going back to the WOT relay If you have voltage on the Pink/Lt blue wire, and no voltage on the black/yellow wire... Check your Red wire and your orange/lt blue wire. These two should both voltage on them with the relay plugged in. If you do not have voltage on on and not the other, replace this relay. If you have voltage on both and still none on the black/yellow wire, replace the relay. If you do not have voltage on either... then the problem lies somewhere else in your vehicle's wiring and this is not allowing your WOT relay to get energized. Just to double check... if you jump the black/yellow wire to the pink/lt. blue wire, you should hear your clutch engage. If it does, then it is either the WOT relay or elsewhere in the vehicle wiring. If it doesn't engage, check the ground wire on the clutch itself (black)
I hope this was of some help without getting too confusing. If I can do anything more now or in the future, do not hesitate to ask. Thank you for the question and good luck in everything.
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