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chris
chris, Ford Mechanic
Category: Ford
Satisfied Customers: 3130
Experience:  ASE Master -Ford senior master-20 years experience
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Ford Crown Victoria LX 1997 Crown Vic A/C -- w/ EATC (LX).

Customer Question

1997 Crown Vic A/C -- w/ EATC (LX). Compressor only comes on w/ cutout relay out & PCM voltage & compressor feed jumpered. Jumped cycling switch (w/ relay in): no comp - disconnected TPS; no comp - disconnected CTS; no comp. ONLY works when jumpered. switched out relays, no change. Any suggestions?
Submitted: 3 years ago.
Category: Ford
Expert:  chris replied 3 years ago.

Hi there

take a look at the wireing pic below

graphic

as you can see there is a fuse in the interior fuse panel that runs through the a/c switch on the dash , and then goes to the low side switch ,, so start at the low side switch and see if there is power there with the key on and a/c om,,,if not then check that fuse in the car ----if there is power at the low side cycling switch ,,then jump the two wires together and move to the high side switch for the a/c ,,this switch should have power going into it and out of it ,,,if it does not then the high side switch is bad.. tell me what you find ,we can go back and forth on this page

-----

Chris

Customer: replied 3 years ago.

Chris,

I've jumped & tested these but i'll try again. I found B+ at the switches & tested the switches w/ a VOM & got full continuity through them (no resistance). I'll try again...

Expert:  chris replied 3 years ago.

ok power runs through the low side switch and then through the high side switch ,,and then to the relay ,,,

also if you remove the relay for the a/c and look on the bottom of it ,,there is numbers next to each pin on the relay ,,, pin 30 and pin 86 ,ware they go into the fuse box should have power on both of them , with engine on and a/c on,,,see if both do or not , with the relay removed see if these two pins ware the relay goes have power

Customer: replied 3 years ago.

Chris,

B+ across both switches; no resistance on switch pins; jumpered both switches, no change. Compressor will still only operate if I jump the relay pins from comp feed to PCM B+ feed (relay out). Otherwise, no comp...

 

W/ key "on", I have B+ from #86, .25 (1/4)V on #30 & a couple of millivolts on #85...

Customer: replied 3 years ago.

BTW, relay clicks when plugged in w/ key on...

 

Expert:  chris replied 3 years ago.

ok, did you remove the relay ,, turn the a/c on and car on ,,and see if you have power at pin 30 and 86 in the fuse box ware the relay went ,,,, with all switches back in place

Customer: replied 3 years ago.
As noted above, w/ key on, relay removed, 12V @ pin 86 but only 1/4V @pin 30...
Expert:  chris replied 3 years ago.
ok,, that pin 30 ,, comes from the high side switch ,,and should have power with car on and a/c on ,,,so its back to the low side switch and high side switch as the problem,,, you said that there is power at the low side switch ,,,, and I think you said the high side switch had power going into it and out of it ,,,,,then this mean there is a open from the high side switch to the relay on the dark green/ orange wire,, so,,,if this wire has power at the high side switch ,with car on and a/c on,,, and there is no power at pin 30 at the relay ,,,then there is a open on that wire,,,, you can run a new wire from the high side switch to the relay or try to find the open ..
Customer: replied 3 years ago.
Just for verification; the high-side switch is the one above the compressor (near the RF corner of the engine) pointing toward the back of the car...
Expert:  chris replied 3 years ago.

below is a pic o the low side switch mounted to the accumilator ,number 4

graphic

and below is a pic on the high side switch ,called the cut off switch

graphic

Customer: replied 3 years ago.

OK, more testing. B+ (12V) at high-side connector (red one); checked continuity from that connector to pin 30 (no resistance, ckt closed), so wire is OK. High-side switch has no resistance (closed) on pins. Is switch still bad..? Does the system have to be evacuated & re-charged to replace it..?

 

I still get no voltage if I jumper the connector..? WTF..?

Expert:  chris replied 3 years ago.
very odd,, you have 12 volts one of the wires at the high side switch ,,,then you jump the two wires together at the high side switch and there is still no power at pin 30 at the relay ,,, but you also checked resistance across the high side switch wire dark green/orange wire to the pin 30 ,,and had no resistance... ?????????????,, that means all is ok ,,,,, very odd,,, now I know you know how to test for power on a cercut,,, but dont take this wrong,,, how are you doing a resistance test on this wire from the high side switch to pin 30 ... ??,, just making sure , dont take this wrong , lol
Customer: replied 3 years ago.

Here are my findings, which have me more confused than ever. I have 12V to Gd on one pin of the h-side connector (w/ IGN & A/C on). I have ZERO resistance on the other pin to pin 30 @ the cutoff relay. But when I jumper the connector, all I get at pin 30 is .25 volts. What am I missing here..? There HAS to be a feasible explanation.

 

No offense taken. Yes, I know how to test. When I place one probe (w/ VOM set on 20K ohms) on the pin one the high-side connector, and the other probe to pin 30, I get no resistance (zeros on the readout, it is digital), same as when I touch the 2 probes to each other w/ the same ohm setting...

Expert:  chris replied 3 years ago.
ok, then I would run a new wire from the conector on the high side switch , green/orange wire , to pin 30 of the relay ,, you can just do a temp wire run not permiment just to see if this repairses the system ,, if you have about 5 feet of wire around , tap into that wire at the high side switch and then rap the other end of the wire on the pin 30 of the rely and plug it in ans see if it works
Customer: replied 3 years ago.
OK, let's try it...
Expert:  chris replied 3 years ago.
good luck
Customer: replied 3 years ago.
All right, now I've gone past my competency level -- I have B+ at the pink wire on the hi-side connector. I ran a jumper wire over to the cutoff relay connector. I checked voltage to the jumper -- I had 13.55V to the body gd on the inner fender. I removed the relay and connected it (still w/ 13.55V) to pin 87 (comp feed). The compressor did NOT engage. But when I jumpered pin 86 (PCM B+) to pin 87 the compressor engaged INSTANTLY. I don't get it. It's getting B+ either way..! Why will it only operate off the PCM voltage supply..?
Expert:  chris replied 3 years ago.

hay ,,,thats a good test you are doing to find ware the problem , is ,, now move to the low side switch and try the hot wire there and run it to pin 87 ,,, if thats ok ,,, plug the low side switch in ,,, then tap into the other wire of the low side switch , key on , a/c on ,, and run it to pin 86 ,,see if it turn the compressor on ,,,, this will help narrow down ware the problem is

Customer: replied 3 years ago.
OK, in process...
Expert:  chris replied 3 years ago.
ok
Customer: replied 3 years ago.

Chris,

Same result. I have the same voltage reading (13+V) coming from both the PCM feed and the lo-side feed. Yet when I jum the lo-side feed to pin 87 I get nothing; when I jumper to the PCM feed the compressor engages (even w/ identical voltage readings on both jumpers)... Is this an amperage issue perhaps..? Why will it run from one 13V feed and not another..?

Expert:  chris replied 3 years ago.
very odd indeed,, it could be a case of high resistance in that power feed ,, but we have to find ware it is -- now we have to go back further --look at the wireing diagram ,, power comes from that fuse 5 in the interior fuse panel then into the a/c switch and out to the low side switch ,, so lets start at that fuse 5 ,,, it may be loose or corroded, ,,run the wire from fuse 5 to the relay pin 87A and see if you can make the compressor work ,, then you have to move to the switch ...
Customer: replied 3 years ago.
All right. And thanks for your patience (thus far), LOL...
Expert:  chris replied 3 years ago.
well got nothing better to do , I broke my collar bone at work two weeks ago,, and cant do much but type
Customer: replied 3 years ago.

Jumper from fuse 5 B+ to pin 87 operates the compressor (same as PCM B+). Next test..? BTW, changed out fuse 5 (it looked OK) & no change... So it wasn't the fuse.

 

Sorry about your collarbone <ouch>, I'm working in 90+ SoCal heat but I'm used to it. I hate cold... LOL

Expert:  chris replied 3 years ago.
ok, you have to access the a/c control switches ,,the back of them ,,, power from that fuse 5 comes on the p/o wire to the back of the a/c controls ,,,do your test from this wire to the pin 87a,,,, if that ok,, then jump that p/o wire to the p wire , basically your by-passing the a/c switch ,,, and see if the a/c compressor turns on ,,,if it does then the a/c switch had high resistance causing the system not to work
Customer: replied 3 years ago.
How hard is it to R&R the control head..?
Expert:  chris replied 3 years ago.

graphic

the panel around the a/c switches pops off,,, then there is four 7 mm bolts that hold the control head in place

Customer: replied 3 years ago.

Grabbing my metric crescent wrench... ;o)

 

Expert:  chris replied 3 years ago.
ok.................
Customer: replied 3 years ago.
OK, test results: Jumper to ppl/or, compressor engages; jumper to ppl (next to it), nothing...
Customer: replied 3 years ago.
Hold on, re-read your post, forgot tojump p/o & p...
Customer: replied 3 years ago.
w/ relay back in & all connections reattached, jumped ppl & ppl/or on control head connector -- compressor DID NOT engage...
Expert:  chris replied 3 years ago.
ok,, just ti make sure ,,, you used a jumper wire from the back of the a/c head p/o wire to the relay and the compressor engages,,, so this means the power input to the a/c control head is ok,,,,,,,,,,,,,,then you jumped the p/o wire to the p wire on the back of the control head conector,,,,,and made sure all switches and relays ware in place , plunged in ,,,and the a/c compressor did not work .......correct ??????
Customer: replied 3 years ago.
Correct. W/ all connections re-connected, I jumped across the p & p/o & no compressor engagement...
Expert:  chris replied 3 years ago.
ok, now run a jumper wire from the back of the a/c control head on the p wire ,,, plug everything back into place and run the other end of the jumper wire to the p wire on the low side switch ,,, you are basically running a new p wire from the control head to the low side switch ,,,,then with all plugged in place, relay in , switches in place , see if the a/c comes on
Customer: replied 3 years ago.
With the control head plugged in or unplugged..?
Expert:  chris replied 3 years ago.

plugged in

Customer: replied 3 years ago.

Chris,

I have tried the following "jumps" with these results: From p/o (where I have power), to the compressor side of the lo-press sw, no comp; from p/o (control head) to comp side of hi-press sw, no comp; from p/o (CH) to pin 30, comp activates.

 

These tests were unplugged, let me plug 'er in & try again...

Expert:  chris replied 3 years ago.

lets go back a little again ,, unplug the control head ,, jump the p/o to the p on the control head conector ,,,,, then go to the low side switch p wire and jump that to 87a in the relay fuse box for the a/c relay ,,,, does the compressor engauge ??????

Customer: replied 3 years ago.
OK, I've tested 7 ways to Sunday. With c/h plugged in, if I jump p/o to pin 87, compressor engages; if I jump p to pin 87 (w/ controls at 60F & max A/C), no comp. Yet I get B+ to gd from either p/o or p. So I take it this means resistance in the switch, correct..? Is there any way to clean it (I've done this w/ electrical switches before w/ good results)..? Or am I doomed to wander the local wrecking yards for another control head..?
Expert:  chris replied 3 years ago.
well,,its worth a try to take the control head apart and try to repaire it ,,,never tried it before,,, but what do you have to loose,,, this car did not change much over the years so ford should still make the part .... good luck
Customer: replied 3 years ago.
Let me give it a shot & report back. If no change, I at least think this isolates the problem. Car has 142K on it now (runs great still) w/ next to no service issues during it's lifetime... I'll go out & try a cleaning on it...
Expert:  chris replied 3 years ago.
ok, sounds good
Customer: replied 3 years ago.

Chris,

OK, after a multitude of tests, re-tests & all else, I finally got the compressor to engage by jumping the p/o & p wires w/ the control head plug disconnected & all else re-connected. That isolated it to the control head switch. Cleaning did not resolve the issue, so now I know that a replacement control head is what I need. I thank you so much for your time, & patience, & hope your collarbone heals quickly. Please respond so I know you got this message & I will accept & checkout. Thanks again..!

Expert:  chris replied 3 years ago.

ok,, thats ,, good, thanks,

Chris

chris, Ford Mechanic
Category: Ford
Satisfied Customers: 3130
Experience: ASE Master -Ford senior master-20 years experience
chris and 6 other Ford Specialists are ready to help you
Customer: replied 3 years ago.
BTW, ran the EATC self-test & came up w/ DTC's 115 & 125 (vss & cts intermittent fail), cleared them & no change. Even diconnected Battery to see if that might re-set anything & no luck. So off to get another control head I go...
Expert:  chris replied 3 years ago.

ok, never has this problem on any other unit like this ,,

good luck

Chris

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