TCCoA Forums banner

1 - 19 of 19 Posts

·
Registered
Joined
·
408 Posts
Discussion Starter #1 (Edited)
I have the analog/manual climate control.
There was no gradual loss of cooling -- one day ice cold, the next day nothing.

The first things I did before consulting my cd service manual was check the fuse and check for compressor seizure. Fuse is good. I can easily turn the compressor with my fingers, which indicates there wasn't a catastrophic loss of pressure at least.

Following the manual, I've checked electricals up to this part of the pinpoint tests:
C5 Check for B+ at A/C pressure cutoff switch harness connector, Circuit 441 (R/Y) to ground.
Is there B+?
Yes No
SERVICE Circuit 441 (R/Y) for open. RESTORE vehicle. RETEST system.
Answer in bold. It seems to me that it's less likely there would be an open in the harness, since there appears to be zero flex involved on this particular section and I've had no other wiring issues on this vehicle.
While I had the connector off, I checked continuity on the cutoff switch as well. That was good.

The Constant Control Relay Module (CCRM) looks to be a pain to get into, with many harness wires. I'd rather not even open the thing, considering the brittleness of other plastic which I've encountered in the engine bay of late -- unless it's absolutely necessary.

Should I perhaps be looking somewhere farther back up the line (e.g., dash control switch or thermo sensor)? I'm assuming the switch is ok, though, since there's B+ at the cycling switch. The thermostat seems to work insofar as moving the vanes (heard, not seen).

I don't have a schematic with this manual. Is there a fusible link somewhere in the a/c line that maybe the manual failed to mention?

Some of you are probably thinking I should perform manifold pressure tests. I haven't, for two reasons:
1. Although I've rebuilt complete a/c systems before, they were R-12 (yeah, it's been a while). Since I had to have a shop supply the R-12 anyway, I had them pull down the system and use their gauges, so I never bought my own set. All I did was replace all the components; well, they did let me help them do the recharge.
2. The troubleshooting flowchart in the manual skips pressure testing if cycling switch jumper does not engage clutch

So, what would be the most likely electrical failure mode for this system? Must I dive into the CCRM or would it be as productive to look elsewhere?
 

·
Super Moderator
Joined
·
9,262 Posts
What happens if you jump the contacts at the connector for the low pressure cycling switch closed with the a/c on?
 

·
Registered
Joined
·
408 Posts
Discussion Starter #3 (Edited)
What happens if you jump the contacts at the connector for the low pressure cycling switch closed with the a/c on?
That was C2 of the tests. No joy, so the manual said proceed to C4 (check B+ at cycling switch).
There was B+, so proceed to C5 as per initial post.

I made an error in the initial post -- edited (manual says skip C3 (pressure test) if C2 (cycling jumper) does not engage clutch).
 

·
Super Moderator
Joined
·
9,262 Posts
There is a high current fuse under the hood for the a/c clutch and there is a fuse in the junction box under the steering column as well. This is in addition to the relay in the CCRM for the clutch.
 

·
Registered
Joined
·
408 Posts
Discussion Starter #5
Do you mean the mega fuse? Coincidentally, I recently replaced the mega fuse sliding cover and I bothered checking it with cover off, so I know that fuse is good. Or were you referring to an a/c fuse elsewhere in the bay?

Looks like I might be looking at a bad relay or at least cold solder joints on the CCRM board. I was hoping to avoid digging into the CCRM. Resoldering (and/or relay repair) is not a prob, as I'm an electronics tech.
 

·
Super Moderator
Joined
·
9,262 Posts
IIRC there's a fuse in the high current fuse panel (what the mega fuse mounts to) for the A/C relay.
 

·
Registered
Joined
·
408 Posts
Discussion Starter #8
I finally got around to yanking the CCRM.

I drilled out the rivets and made a visual inspection of the PCB. The solder joints appeared in great shape and the factory applied a rubbery conformal coating all over it for corrosion protection. There was no evidence of overheating. either on the board or the components.

I got started on it late in the day and by the time I drilled it and found appropriate screw/split ring/nut combos in my parts bin for the four corners, I didn't have time to actually put the board on my bench to test the relays (needed the car in operation that evening).

But, since it's all drilled and prepped, next time it will be quick to pull it and do the tests. I'll post some pics of my CCRM when I disassemble it next time.
 

·
Registered
Joined
·
408 Posts
Discussion Starter #9 (Edited)
Welp, I put the CCRM on my bench and the relays are good. I didn't find any xistors shorted or open - just a quick check with a DMM; I have yet to fully test them with my TF46. The diodes all test ok. This damn silicone coating is aggravating; probes keep slipping when ya try to pierce it!

Am I missing something here or would you suspect the PCM at this point?


Was gonna put up some pics, but I found an old thread with them already: http://forums.tccoa.com/showthread.php?t=136194&highlight=relay+module.
The diff is that mine has only 4 relays as opposed to the 5 shown in that other thread and a sink-mounted xistor which is missing from said 5-relay version (IRCM).
 

·
Registered
Joined
·
7,062 Posts
Where in Texas are you?
 

·
Registered
Joined
·
408 Posts
Discussion Starter #11
Houston area, also.

I did more tests on the CCRM and am convinced this is not the problem area; must be farther up the line. Sure would like to own a breakout box for this car!
 

·
Registered
Joined
·
7,062 Posts
Houston area, also.

I did more tests on the CCRM and am convinced this is not the problem area; must be farther up the line. Sure would like to own a breakout box for this car!
Ok cool. Might have time to help.

I think you might be making this much more difficult than it really is.
 

·
Registered
Joined
·
408 Posts
Discussion Starter #13 (Edited)
I neglected to mention that the OP step C5 result is no longer valid -- must not have had my DMM probe adequately inserted into the cutoff switch connector the first time!

I shorted the cycling harness again, got my B+ at the pressure cutoff switch (which has continuity), then checked that line (circuit 883, PK/LB) back to CCRM pin 21, where there's good B+ .

Since the CCRM relay is confirmed functional, the obvious source of the trouble is pre-CCRM -- there's nothing coming into the CCRM to energize the relay coil.

I am now at this point:
C8 CHECK PCM INPUT VOLTAGE FROM A/C PRESSURE CUTOFF SWITCH
Engine off and ignition switch in RUN position.
Set A/C control to MAX A/C.
Using a voltmeter, check for voltage at PCM Circuit 883 (PK/LB) Pin 41 (4.6L), Pin 10 (3.8L).
Which is going to be rather difficult to do if I can't get behind the PCM harness connector with a probe tip or at least a short wire to clip a probe to. Hmm.. the PCED says leave the PCM disconnected, so I should be able to get in there after all.

Speaking of the PCM, I scanned it the other day; no DTC's. I didn't try to look at ACCS/WAC PID's 1101/1104 at the time. My consumer scanner (actron Elite CP9185) reports that the vehicle doesn't provide output control anyway, so I can't attack the problem that way.

I've also browsed through the exhaustive PCED pinpoint tests, most of which are simplified in the workshop section of the manual. There seems to be little more I can do at this point other than check at the PCM harness connector or start easter-egging and throwing replacement parts at the problem.

It could be other things, such as a bad dash control or damper door switch, etc., which would be preferable to worst case scenario PCM. The door would be a pain to get at, but it should be a much cheaper fix than a PCM.
 

·
Registered
Joined
·
1,252 Posts
Check your B+ at the low pressure switch with a test light not a DVM. Keep moving down the circuit with the test light until you get to the compressor clutch.

I chased my tail using a DVM on my Town Car. Even though the DVM read B+ at the low pressure switch the light did not light. It turned out to be the control unit in the car had a bad relay in it.
 

·
Registered
Joined
·
408 Posts
Discussion Starter #15
argh! The PCED threw me. It says to check the coil of the relay:

X106 CHECK WAC CIRCUIT AND WAC RELAY IN CCRM
Key off.
Disconnect CCRM
Check WAC relay coil resistance:
Measure resistance between pin 22 and pin 24 of the CCRM
.
Resistance should be between 65 and 120 ohms.
Check CCRM for internal short circuit:
Measure resitance of CCRM betwen pin 22 and the following pins: 1 through 11, 13, 15 and 21.
Measure resistance between pin 22 and the CCRM case.
Each resistance should be greater than 1000 ohms.
When in fact the a/c relay (on this model) doesn't use a coil, it's a silicon switcher! I had mistaken the smaller Omron fuel pump relay for the a/c relay.
It's only after I found the CCRM schematic in the PCED that it hit me. :bangwall:

So, my bird does have five "relays", after all: EEC, Fan Low, Fan High, Fuel Pump and this solid state a/c one.
I had mistaken the transistors as some sort of ancillary protection circuit for the PCM. :facepalm:

Now that I know what does what in this thing, I'm going to pull the transistors and check 'em out-of-circuit with my TF46 for conclusive go/no-go proof one way or another; if go, I should probably check gain against data sheets while I'm at it, for good measure. I'm tired of looking at this CCRM and don't want to have to revisit it.
 

·
Super Moderator
Joined
·
4,926 Posts
Hopefully you're documenting the schematics and part values as you go along *grins*

RwP
 

·
Registered
Joined
·
408 Posts
Discussion Starter #17
I completed testing of the CCRM. No doubt remains, it is good, so the prob is upstream or downstream of that.

I took lots of pics while I had the box disassembled, so I'll post 'em up.
Unfortunately, it seems this forum isn't friendly to slideshow embedding in posts. I tried Flickr and Picasa; feature not yet available on the new Photobucket. The closest I got to having a semi-viable slideshow was wrapping
Code:
 tags around the embed string provided by Picasa, and that wasn't quite right even after enlarging its frame (i.e., spacing it out after the opening code tag)..

I should probably start a dedicated thread for this, since it goes into detail on one specific a/c component -- which is no longer relevant to this thread subject, because it tested good.
My unit and the info I will/would present are sufficiently different from the previously linked CCRM thread as to justify independent treatment, IMHO.
 

·
Registered
Joined
·
408 Posts
Discussion Starter #18
Welp, I finally got around to checking the clutch coil and clutch>GND resistances and they're within spec.
The CCRM is definitely functional. Via jumpers, I simulated removal of CCRM pin 22 on my bench, and there's good B+ out from the A/C SSR relay.
On vehicle, there's good B+ going to the CCRM, but no B+ to the clutch.

Does this look like a PCM partial failure to you? I'm wondering how often the PCM is at fault vs. other things like damper door switch, throttle sensor, etc. I suppose a permanent WOT signal would cause the PCM to disengage the clutch, but wouldn't there be other, persistent WOT symptoms with the vehicle?

Having no breakout box, I can try to get behind the PCM harness connector with a small solid wire (22AWG or so) to clip my DMM probe to.
Has anyone done this in a pinch or is it pretty much inacessible for testing w/o the breakout box? I realize one can't [easily] disconnect given conductors as the manual advises, but just for voltage and resistance checks will I be able to get at that connector or should I not even waste my time trying?
 

·
Registered
Joined
·
408 Posts
Discussion Starter #19 (Edited)
update, plus a service port query

I recently bought a new gauge kit (FJC 6766P) and it reads extremely low pressure on both sides.
The pressure was initially around 10psi, but I lost more from the hi side when the valve stuck open!

Ok, so low pressure (i.e., a leak somewhere) is at least partly responsible for the clutch not engaging.
However, since shorting the cycling switch and verifying the cut-off switch had continuity to the clutch didn't force clutch engagement, it seems there's more going on than merely a near-empty system.

I'll know more after I add some refrigerant and see what happens at around 50psi, as per service manual (although in another section, the manual specs 60-80psi with engine not running).

I have an old vac pump which isn't up to the task, so I'm going to bite the bullet and do this job right with a new pump, a new scale and a 30lb. tank.

I'll suffer refrigerant loss during the process of leak discovery, so doing this with cans is pointless. I could just tear down the entire system and slap new seals on it all around and use 3 full cans (Ford thoughtfully designed the system to use 36oz.), but I might find a leak in the evap or condenser core(s) and new seals ainta gonna fix that (plus.. back to the store for more cans).
Also, this probably won't be the last time I visit this Bird's a/c, so I figured I'd better have a big tank handy. I don't expect to get another 16 years out of the a/c, maybe 15! :crazy: :D
Then there's the economics -- nowadays eight 12oz. cans cost as much as one 30lb. tank!

Any advice on a new scale? I've read up on lots of them and I'm currently leaning toward the TIF9010A. I don't think I'll need a programmable one and certainly not an auto-shut-off solenoid, since I'll be paying close attention to what I'm doing.

Now, the valve:
I couldn't get the hi side to close after I disconnected my gauges, and I assumed the system would be completely discharged next time I checked it, even though I did put the port cap back on.
Well, I went out today (weeks later) and discovered that it still has pressure and the valve managed to eventually seat itself! yay..

I still don't trust that valve, though, so I'm going to [hopefully] replace it and maybe the lo side one while I have the system empty.

My '96 appears to have a combination of port styles. The lo side has wrench flats, so it's definitely a 2-piece type. The hi side has no flats, BUT appears to nevertheless be a 2-piece type, because it has an inner rubber cap atop the valve plunger, just like the lo side valve.
As depicted in the service manual, the inner cap seats against the top of the valve bore.

Is the hi side indeed a 2-piece type, even though there are no wrench flats?
If I must replace the port as a whole unit anyway, it won't matter if I damage it with a pipe wrench; I'm just making certain I won't be twisting on a 1-piece port by mistake!

Anybody know a good source for the ports? I haven't been able to find aftermarkets (Rock Auto, etc.).
 
1 - 19 of 19 Posts
Top