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'88 Xj: Aux Fan & AC Clutch Inoperable - Help Requested

R

RAVC1

NAXJA Forum User
Location
Michigan
I suspected the auxiliary engine cooling fan was not working. I just proved this thought to be correct. I changed the relay (with a second used relay - in front of the washer fluid reservoir) and the fan was still inoperable. At this stage of involvement I was thinking dirty connections, poor ground, etc. Although the relay could be bad.

I recalled the auxiliary fan always rotates when the AC is turned on so I engaged the AC. The auxiliary fan did not move, yet I know it worked with the AC last summer. I repeated this a few more times to be sure then I noticed my compressor clutch was not engaging.

Now it appears I have a larger system issue. Unfortunately, I will be educating myself on these systems with this set of problems.

If anyone can offer me assistance with these issues I greatly appreciate it.

Rick
 
Well, if the system has lost its charge the low pressure switch will prevent the compressor from engaging.

Try this: use two pieces of wire and jump a ground and positive to the aux fan direct from the battery--if it runs, then your fan is good. If it doesn't, then the fan itself is bad. Second, jump the low pressure switch and see if the compressor will engage.
 
Hello Joe,

Thanks for responding. I had planned to jump the fan in the morning. I suspected the AC system might not enable if the refrigerant were gone. I'm uncertain regarding the state of charge as I know I overlooked exercising my AC clutch routinely during winter as I usually do. The repairs to AC system were made 2 years ago so, I hope it is something else as refrigerant is costly these days.

Rick
 
RAVC1 said:
Hello Joe,

Thanks for responding. I had planned to jump the fan in the morning. I suspected the AC system might not enable if the refrigerant were gone. I'm uncertain regarding the state of charge as I know I overlooked exercising my AC clutch routinely during winter as I usually do. The repairs to AC system were made 2 years ago so, I hope it is something else as refrigerant is costly these days.

Rick
Click to expand...

Have you converted to R134A/substitute yet?
 
It is easier to use a jumper wire across the connections that radiator temperature switch is connected to simulating the switch to be on. Then if the fan still does not work, try your suggestion.

joe_peters said:
Well, if the system has lost its charge the low pressure switch will prevent the compressor from engaging.

Try this: use two pieces of wire and jump a ground and positive to the aux fan direct from the battery--if it runs, then your fan is good. If it doesn't, then the fan itself is bad. Second, jump the low pressure switch and see if the compressor will engage.
Click to expand...
 
Joe, et al,

Yes, R134. However, my clutch issue could also be the relay located in the right hand shock tower area. I cleaned this area excessively late last summer when I lost ignition due to dirt buildup on my CPS and oxidation on my ignition module & coil terminals.

I have (2) working Renix vintage auxiliary fans. Now I need to check:

1 - Ground at aux. fan mating connector,
2 - Aux. fan relay,
3 - Aux. fan diode assembly.

Then I can diagnose my inoperable AC clutch.

Rick
 
The relay for my auxiliary fan is bad. I fabricated a jumper and placed it in sockets 1 & 4 and the fan moved air.

I jumped the low pressure AC switch (on my receiver/dryer) and this did not result in the clutch engaging. I then exchanged two of the four relays in the right hand shock tower area to evaluate the relay and this did not engage the clutch either. Now I'm getting puzzled. Clearly, I also need to check the wires to the AC clutch to ensure its pigtail and the the lead it connects to are sound. I suppose the clutch could have died as well. If this is true would the clutch produce a burning smell?

Rick
 
There is thermal switch in the lower left of the radiator (left is always as you are sitting in the drivers seat, in mechanics speak). The switch closes when the temp is high enough and energizes the relay, with the ignition on.

You touch the two thermal switch wires together with the ignition on and the fan should fire up.

My guess is you have a power problem in the A/C circuit. Either no power to the cab switches, the relay or maybe ECU isn't grounding the A/C relay.

I'd do some volt tests, volt meter or even a trouble light. Figure out where and why the power is interupted.

Does the blower motor work heat or A/C? If it doesn't this is a good sign you have a major power problem and we can work upstream from there. If it (blower motor) does work it is likely a downstream problem.

Relays don't often go bad, it happens but it is rare, most times it is something else.
 
Last edited:
8Mud,

Good thoughts.

I know of the radiator switch and had planned to install a cabin switch featuring a harness jumping these switch terminals (this is discussed elsewhere here in NAXJA) so, I could have manual override merely for the sake of insurance/confidence purposes. This switch acts via the diode assembly and the auxiliary fan relay to control the fan.

I recently thought of exchanging the HVAC cabin control as a test for that component because, I have a known good spare.

Yes, my blower motor works when positioned for heat, vent or any of the AC settings. I just do not get cold air in the cabin when I set it for the AC. I have rejected my engine heat the last two days on my 1 h commute home in slow moving traffic.

Your point regarding relays is understood, but now that my aux fan relay has failed it is the second relay I have been required to replace in the last 10 months. My starter relay was replaced last August.

I forgot to mention that the sight glass on my receiver/drier is silver. I do not see any color and I thought we were supposed to. I just cannot recall what the color is supposed to be...green?

Rick
 
My sight glass is clear or I'm looking at the bottom bare metal when I look in there. Some sight glasses have a moisture indicator (green good, red moisture), haven't seen any on an XJ.

Freon is colorless, though the refrigerant oil will sometimes give it a very light tint.

Usually when I first fire up my AC the sight glass passes some bubbles then fills with clear freon. Hard to tell when it is full and empty, part full is easy to see.

Possible your thermostat is faulty, but before I do any component swaps I always check for power and make sure the connectors, grounds and harness (wires) are good. I'd say conservatively, the problems I find are may 60-70% in the wiring and maybe 30-40% in a component.

Relays can fail, but I'd first make sure the relay is actuating the coil inside (continuity), the relay has continuity when actuated and when it latches it passes current. Most times the failure mode for a relay is fryed contacts, sometimes a spring pops off. When the contacts fry it usually indicates a deeper problem, like why did they fry? I swap out relays just to eliminate them as a possible problem, but I have the relays out of my 87, that are still OK.

The next time you go to a junk yard find an older BMW and yank all the 30 amp Bosch relays out of there, Bosch *premium* relays last.

Between Mike, Joe, Cruiser and a few others, we've likely spent thousands of hours picking our way through the Renix electrical. I find it interesting, kind of like studying a Platypus, one of nature's oddities. Designed by the French and basically grafted onto an American host and built by Mexicans. LOL
 
8Mud,

Please don't ask me about the French...

I too enjoy the Renix vintage Xj's. I have had (3). Call me sick, but yes I like the challenge.

I repeated the aux fan on test as you stipulated earlier. That is, I jumped the harness connector for the radiator switch with key ON. The fan rotated even with one of my bad relays. I'm uncertain if this adds new information to my method of installing the jumper wire in the relay socket. However, I was just attempting to test the fan with my test. Yours may be more thorough.

I am finding I lack power at the AC clutch. My test light is working correctly, but I cannot determine why the smaller of the two tube connectors (on the orange wire) does not possess 12 VDC. I think this is what I need to track down. I had key ON and the same suspect aux fan relay as used above in its socket for this test. AC modes were selected on the cabin control and still no power on this small diameter connector (easily traced to the ac clutch). My AC clutch ground is sound.

Rick
 
I'm fairly certain the motor has to be running for there to be power to the A/C clutch.

I've never had many issues with my A/C so I may not be the one to ask about this. I have seen more than a few Aux fan issues though.

From the schematic the A/C relay needs the pressure switch closed for power to the 87 pin of the A/C relay and the thermostat to be closed to signal the ECU to ground the A/C relay actuator coil and power from the fuel pump relay to the A/C relay actuator coil. The fuel pump relay closes when the engine is running.

I really don't know if the thermostat is NO or NC, I've never had one go bad.
 
8Mud,

With time & additional effort I now think you are completely correct in that I have a power or, power distribution issue. I recently used my test light to jump the B+ terminal of the battery to pin 5 of the aux fan relay socket. This rotated the aux fan. This indicates my aux fan relay is fine and my 'usual' sources of 12 VDC to pin 5 on the aux fan relay socket are not.

Rick
 
8Mud,

I began looking at the screw terminal on the start relay. This is where many of the B+ leads begin. Most of the insulation near the ring terminal is swollen and softer than that downstream by as little as an inch. All the local auto parts stores tell me they (should) have suitable replacement material, but I want to ensure success the first time.

Anyone have experience replacing their fusible links in this section of the wiring harness? I would like to resolve these issues tomorrow if feasible, but beter information is worth waiting for.

Rick
 
RAVC1 said:
8Mud,

I began looking at the screw terminal on the start relay. This is where many of the B+ leads begin. Most of the insulation near the ring terminal is swollen and softer than that downstream by as little as an inch. All the local auto parts stores tell me they (should) have suitable replacement material, but I want to ensure success the first time.

Anyone have experience replacing their fusible links in this section of the wiring harness? I would like to resolve these issues tomorrow if feasible, but beter information is worth waiting for.

Rick
Click to expand...

PM 5-90 or search--you can replace those fusible links with other types of fuses.
 
If you jumped the thermal switch and the relay fired up the aux fan you are good on that circuit. The only other possible problem would be if the aux fan didn't come on when the temperature gauge showed well above the center point, then you *may* have a faulty thermal switch. Thermal switches don't often go bad, but they do get lazy with age and the aux fan may come on later than it should.

The power to the climate controls and most of the A/C system is the brown wire from the ignition switch then through the blower fuse. If the blower is working, you have power in this circuit.

Do you have power to one leg of the pressure switch, with the A/C on? Do you have power through the pressure switch? Do you have power to the 87 pin at the A/C relay?

If the thermostat is faulty the ECU won't ground the A/C relay actuator coil. The sole function of the thermostat is to keep the evaporator from freezing up. It opens the clutch (A/C relay) when the evaporator gets too cold.

Think like a mouse following a maze and check every stop (connector) or event (relay, switch, thermostat etc.) along it's path.
 
clogged radiator over cools a slow moving coolant volume and keeps the thermal switch from tripping the fan too.
 
Joe, 8Mud & Ecomike,

Awake and back at it today. My garden tractor had to be torn apart to reassemble the starter after I signed off last evening. I have to complete this repair before resuming the Xj work.

I do not like the condition of the insulation at my starter relay so I'll follow Joe's suggestion to search for replacing fusible links with fuses next. I may not have a problem with this currently, but avoiding one is preferred. Rock Auto is excellent for solving 'future' problems. Ironically, the worst sets of wires are both org/grn pairs...one of these pairs is for the aux fan (according to my '89 FSM - my '88 FSM is on my pc that does not currently boot.)

I checked my grounds in front of the washer fluid reservoir yesterday as well. The black wire in the aux fan relay socket is grounded at this location. All appeared fine. I will check the resistance of my thermostat switch to see if this offers any clues because, I was surprised when the fan rotated when I jumped the 12 VDC directly to the aux fan input/orange wire yesterday.

I'll need to check these suggestions for the AC power and the thermostat. So far, inadequate grounding of the AC relay makes sense as a possibility for my inoperative clutch. I also realized it could be too far from the magnet and cannot be pulled in to engage. Regardless, I need to determine why I do not have power at the clutch first. I am fairly certain my memory can still hear/sense the ac clutch engaging in the recent past.

Thanks.
 
I think I can safely conclude my radiator thermo switch is bad and this is the reason my aux fan does not energize. I pulled into the drive a few minutes ago and let the engine idle so the coolant temperature would increase. I had the hood open before the gauge (for the sensor at the left rear corner of the cylinder head) reached 210F, and the fan was still off. I went to get my test light and jumped B+ to the input terminal (org wire) of the aux fan relay socket and the aux fan has been running continuously since. The coolant temp is decreasing, but it does not happen quickly with the OE aux fan. I guess I need to assess that Taurus fan conversion more seriously...

More on the AC clutch power issue later.

Rick
 
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