When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Neither cooling fans come on when I press the AC button, so I used ALLData, the first thing it told me to check was the AC pressure switch connector, it said that it should have 12v but instead I got 10v, next thing to test is the AC diode, but I can't find it. Slowly I've noticed that the someone before me has done some rewiring, like how on the pressure switch connector the red/wht wire is suppose to be power but for some reason blu/wht (it actually should've been a grn/wht not blue/wht) has power or when I was testing the ignition switch I notice that the connector has different colored wires going into it and the terminals are mirrored (like how constant battery terminal has a yellow wire when it should be a white wire and the terminal is in the top left instead of the top right). Based on this picture it should be near the fuse box somewhere above what I think are relays. With that said I have no idea how to find this diode, so I was wondering if any of you guys have any tips on how to find it.
I'm thinking about going to a savage yard to search for a diode to make sure I'm not going crazy and I have a backup diode just in case the one in my car is bad.
It is part of the Main Wire Harness, plugged into a black connector (Connector C423). It may be wrapped with some electrical tape on the main wire harness loom.
Maybe I'm not looking hard enough but I didn't see it on the main wiring harness, the first question would be is the connector attached to the body like how some of the wiring harnesses have body panel clips to attach itself to the body, also how big is connector? I know it's a diode that has 2 wires going into so I imagine it's not that big but you knowing getting a reference to its size wouldn't hurt.
This photo is from a member's 1996 Accord I helped on another forum regarding power door locks. But, at the top left area, you can see a Red/Wht wire and a Green wire; those wires lead to the connector for the A/C diode.
I found it, it was wrapped in tape with the wiring harness loom so I couldn't see it until I cut off some of the tape.
So if I'm reading the diagram right I should be getting resistance from B to A while none from A to B right? Because when I test it I'm getting resistance from A to B while I get none from B to A. Just to be sure I'm not being stupid I have the red multimeter lead on A and the black lead on B, with that setup I should be getting no resistance?
The service manual test is to check that current flow in one direction only. If it flows in both directions, it is faulty.
When the red positive test lead is on the anode side (A) and the black negative lead is on the cathode side (B), there should be current flow. When the test leads are reversed, there should be no current flow. - Your tests are consistent with this.
If your multimeter has a Diode Test Mode, that would be the best approach vs just resistance testing alone. But, regardless of using the utilizing the diode test mode (if equipped), your diode is most likely good.
Ah, in that case yeah I am getting a voltage of 0.5v in one direction but not the other, so in that sense the diode is fine. I need to go back and check if I'm getting battery voltage at the A/C pressure switch connector, I hope its at battery voltage otherwise I'm screwed.
Generally, no, a bad radiator fan would not a cause the A/C to not run. The fan runs when the A/C is on; but, is not a component that would stop the A/C from running.
I vaguely remember someone I helped on another forum where the O/P initially focused on the A/C diode, after he found the A/C diode was okay; his own further diagnostics found the A/C thermostat was the cause of his issues.
You should keep at it and ask questions even if I or someone else may not end up giving you the solution. You may solve it yourself when you get your thoughts going. You remind me of that other person I referred to in the other forum; but, younger. You were like him, testing, thinking logically, thinking of other causes, etc.
Well that's one way to put a big-dumb smile on my face. I asked because weeks ago when I had a mechanic put refrigerant in my car, there were no leaks, the compressor was new so it should work, but it didn't. The fans weren't cutting on, he told me I should replace them, in my experience the fans do come on its just that the radiator fan rattles a lot for a while - okay since I got the car I've ignored it but recently since the mechanic brought it up and my general annoyance building up I've decided to replace, actually I got a new fan in my living room. I just needed someone more knowledgeable with Hondas to correct me on that. So at this point I'm not sure if I should test the A/C thermostat or go back and figure out why I'm getting 10v at the A/C pressure switch connector.
This is some info. of how part of the circuit works:
When you push the A/C switch ON, and the heater fan switch is in position 1, 2, 3, or 4, a “ground” input is provided to the ECM/PCM through the A/C thermostat and the A/C pressure switch. The A/C compressor clutch relay is grounded by the ECM/PCM. When energized, the relay allows battery voltage to energize the compressor clutch coil which then engages the clutch.
Technical info. regarding how the A/C thermostat works:
The A/C thermostat is essentially a switch to control the A/C clutch cycling. The A/C thermostat for your model year car is principally comprised of a thermal resistor (thermistor) and a transistor (used as a switch).
The A/C thermostat has a three-wire connector.
For a transistor, current flow from Emitter to Collector and that flow is controlled by current applied to the middle terminal Base. The Blk/Yel wire coming through Fuse No. 8 (7.5A) from the under-dash fuse box is the 12 volt power source (+) which applies power to the transistor’s middle terminal (Base). (See diagram in the third image above, and this link regarding transistor to gain a better understanding.) TRANSISTOR | JOEL
The 12 volt power going to the transistor Base, is also controlled by the thermistor. The resistance at the thermistor changes with temperature; so, the lower the temperature, the higher the resistance. If the temperature is below 37 degrees F, the resistance would be high, which would then limit current to the transistor Base; effectively cycling the A/C compressor off.
The Blu/Red wire would be the wire to supply the ground (-) when the A/C switch is ON, and the heater fan switch is in position 1, 2, 3, or 4. The Blu/Red wire runs through to the transistor’s Emitter.
If the ignition, A/C , fan switch is turned on, and the temperature at the thermistor is above 37 degrees F, the ground signal should go through the transistor to the Collector (where the Blu/Yel wire is connected) and further through the A/C compressor circuit. This is assuming the thermistor and the transistor in the A/C thermostat is working properly.
I did, just tested the connector. I'm getting no voltage in blu/yel on the A/C thermostat connector. I guess I found the culprit, if I'm reading it right blu/yel comes from the A/C pressure switch, when I think about it I don't think I've tested the continuity of the pressure switch, I'm going to go do that.
I added notes and directional arrows to the circuit diagram based on my understanding of how the circuit works:
The A/C thermostat for your car is a discontinued part; so, if you find one in a salvage yard for a few bucks, that would be great. The other guy I previously referred to, I believe picked one up for $5 from the salvage yard by pulling it himself.
I found a different thread on Honda-Tech where this guy determined his A/C thermostat was bad on his Civic. Since he couldn't readily get the OE thermostat, he went with an alternative.
Looking for the AC diode in a 1997
