MikeF

Had the car in for routine maintenance and asked the mechanic to run fault codes...just for fun. Well, he came back to me with three codes, one for the oil cooler blower, one for the AC condensor blower, and one for a stage 2 blower (what is this?). Could all these blowers be dead and the car still operate perfectly? I checked fuses and the oil cooler fuse was blown. Put in a new 30A fuse and let the car get good and hot...I did not hear any fan kick on near the oil cooler. Temp guage never reached above the midpoint on the guage. I've never had a hi-temp problem.

Any thoughts?

Thanks,

Randall G.

Hi Mike,

>Could all these blowers be dead and the car still operate perfectly?

Well, not perfectly or optimally, but it will operate okay. With respect to the A/C condenser blower, your A/C won't be as efficient, but will still blow cold air. With respect to the oil cooler fan, the oil cooler is very efficient, and will keep the oil from getting too hot, even without an operating fan. Many 964/993 owners are driving about with OOS oil cooler fans, as the effect is not gross. But, in reality, your oil could be cooler.

>stage 2 blower (what is this?).

This usually refers to fast or high-speed operation, as compared to slow or low-speed operation. For example, the stage 2 blower for the oil cooler is actually the same fan as stage 1 (slow-speed), but operating in fast-speed.

Your A/C condenser fan should come on with your A/C (ignition on). If it doesn't, something is amiss.

The most common cause of OOS A/C condenser/oil cooler fans is the resistor that is in series between the slow-speed relay power and the motor. However, there are other possible causes, such as the relay and climate control unit.

To easiest way to verify your fan motors are okay is to perform a jumper test, as described here:

<a href="http://members.rennlist.com/rgranaas/rgranaas.htm" target="_blank">Oil Cooler Fan Ops Summary</a>

Lots of other information on troubleshooting, as well.

Best of luck!

MikeF

RG...You da man!!! I printed your instructions and did some jumping. All fans work fine...I could only get a high speed fan on the AC by jumping from 3 to 5. At 3 to 7 there was no low speed fan for AC...should there be? What's intresting is that I turned on the AC (first time in a while) and the fan came on...stayed on for a few seconds, kicked off, then back on again. It continues this cycle and I can hear the relay click each time it kicks on and off. Safe to assume this is normal? I switched relays and it did the same thing, so I assume relays are OK.

Also, since I got a low and high speed fan on the oil cooler, is it safe to assume that the relay (AC switch confirmation), the fans, and the resistors are OK? Now I'm wondering if the fault codes were old, uncleared codes from the PO!!! Or, if the oil cooler blown fuse caused the fault code. Any thoughts?

My temp guage never gets much above 9 o'clock. I'm wondering if the low speed fan came on and I just couldn't hear it with the engine running.

Thanks for your help with all these questions. I think I was about to be taken to the cleaners!

Rgds,

Randall G.

Good morning Mike,

&gt;At 3 to 7 there was no low speed fan for AC...should there be?

Unfortunately, yes. This is pretty much positive indication that your A/C condenser resistor has failed.

&gt; What's intresting is that I turned on the AC (first time in a while) and the fan came on...stayed on for a few seconds, kicked off, then back on again. It continues this cycle and I can hear the relay click each time it kicks on and off. Safe to assume this is normal?

This is unusual, not normal. Was the fan starting in slow-speed or fast-speed? I'm guessing your resistor is working on an intermittent basis. For example, I know of a few 993 owners who's oil cooler fan would come on, but only run for about 10s (not long enough to do any good). Apparently, the resistor is mainly failed, but completes the circuit intermittently.

&gt;Also, since I got a low and high speed fan on the oil cooler, is it safe to assume that
the relay (AC switch confirmation), the fans, and the resistors are OK? Now I'm wondering if the fault codes were old, uncleared codes from the PO!!! Or, if the oil cooler blown fuse caused the fault code. Any thoughts?

I think your relays are fine, based on the A/C condenser fan behaving the same after a swap. I believe the A/C condenser blower fault is being caused by a faulty resistor. I believe the blown fuse caused the error codes for both the oil cooler fan and stage 2 blower--stage 2 being fast-speed. The oil cooler blower fuse is in series for both slow and fast-speed. So, an error would pop up for both in a test if the fuse was blown.

To be completely sure your oil cooler fan is fine, I would do the following: If you let your car idle long enough in the garage, it should get warm enough for the oil cooler fan to start. To expedite the warming process, you can place an "industrial style" blanket over the rear spoiler grille (a trick I learned from Andial)--this will really get the engine warm in a hurry. At somewhere near the 9:00 mark, the fan should start and keep running until it has actually cooled the oil. If your fan behaves as such, it's certainly A-Ok.

With respect to your A/C condenser fan, I believe your next step is to take resistance readings between terminals #5 & #7 of relay R14. If it doesn't come back near 0.6 ohms (the resistor is 0.45 ohms), you have positive confirmation the resistor is failed. Oh, and you can also do the same (resistance readings between #5/#7) for the oil cooler fan resistor while you're at it.

Best of luck, and look forward to hearing what you learn.

MikeF

Randall,

OK, I let the engine warm up with blanket over rear deck lid. At 9 o'clock, nothing happened. I let it continue until 10 o'clock and still nothing. I shut it off after that. I disconnected the lead going to the oil temp sensor. I restarted the car and the fan came on full speed and cooled things right down. It stays on all the time...does not shut off even once temp is below 100c. Does this mean that my temp sensor is shot? I can probably get one on Monday and pop it in. Look forward to your response. I assume it's OK to leave the temp sensor disconnected...keep engine nice and cool.

Now to check resistance on the AC side.

MikeF

RG...here's more:

Checked resistance between 5 and 7. On the AC side...no reading...bad resistor? On the Oil Cooler side, the reading jumped around a bit but I'd have to say it was around .02-.03 ohms. Also, just for grins, I connected multimeter to each of the oil temp sensor leads and got a stable reading of 4V. Any ideas?

If that is the resistor on top of the oil cooler...yes, its a PITA to get to.

Thanks for your help.

Randall G.

Hi Mike,

&gt;Checked resistance between 5 and 7. On the AC side...no reading...bad resistor?

Yes, sounds like an open circuit, which means bad resistor.

&gt; On the Oil Cooler side, the reading jumped around a bit but I'd have to say it was around .02-.03 ohms.

Do you mean 0.2-0.3 ohms? 0.02 is too low by a factor of ten, as the resistor itself is 0.45 ohms. Anyway, besides having continuity, the fact that the fan ran when jumpered in slow-speed is pretty good indication that your resistor is okay.

&gt;OK, I let the engine warm up with blanket over rear deck lid. At 9 o'clock, nothing
happened. I let it continue until 10 o'clock and still nothing.

Doesn't sound good ... your fan should have started by then.

&gt;I restarted the car and the fan came on full speed and cooled things right down. It stays on all the time...does not shut off even once temp is below 100c. Does this mean that my temp sensor is shot?

When you disconnect the oil cooler temperature sensor, the climate control unit sees an open circuit, and starts the fan in the default (worst case) mode = fast-speed. It will run continuously in fast-speed as long as the sensor is disconnected. This does not mean the sensor is bad.

&gt;I assume it's OK to leave the temp sensor disconnected...keep engine nice and cool.

Yes, it's okay. Actually, several owners have disconnected their temp. sensor permanently because they like how cool the car runs. The only downside is extra wear on the fan, but at about $100 for a replacement, they reason it's worth the reduced engine wear. It's also pretty loud in fast-speed, and that's why I designed a jumper to run the fan continuously in slow-speed.

Looks like you're into a full-blown troubleshooting effort for your oil cooler fan. For example: 1) resistance readings of the sensor as it warms up 2) voltage drop across the resistor with fan jumpered in slow-speed--more verification that the resistor is okay 3) continuity between the CCU and relay/sensor.

Good luck! I'll catch up with you later today--off to catch a matinee of the Lord of the Rings.

MikeF

Ha! Sounds like we had a similar day. Had to abandon my efforts as I promised my son that I'd take him to see Jimm Neutron this afternoon.

Well...I'm nearing the end of my diagnostic hunt...as you can tell, I'm an amature, at best, with a multi-meter. You're probably right about the reading being .2-.3, either way, I'm feeling OK about the oil cooler resistor. For under $20, I think the next step will be to change out my oil temp sensor and hope for the best...agree? Plan B will be to copy your low speed jumper. I assume I can buy the necessary resistors at Radio Shack and wire it from #6 to ground as you suggest.

I will also pick up a ballast resistor for the AC side and attempt finding and changing it...but this is lower priority.

Thanks again for your help and advice. Hopefully others can learn from this...I know I am.

Randall G.

Hi Mike,

&gt;Thanks again for your help and advice

My pleasure!

A few more thoughts. Try repeating the resistance readings. If you're actually reading something like 2,000 or 20,000 ohms--or even 20 ohms, that's no good. While you have continuity, the voltage getting past the resistor to the motor will be insufficient to turn the motor. Also, if your jumper is of sufficient gauge, try leaving it installed for awhile to see if the slow-speed fan cuts out. If it does, it's a good chance your resistor is failing intermittently. FWIW, several owners have had dual failed resistors--i.e., both the A/C condenser and oil cooler fan.

Talk to you soon!

MikeF

When I took the readings, the car was off. Should I have measured the resistance between 5 and 7 with the ingition on? Also, since the oil temp sensor is now disconnected, will it still give correct readings?

MikeF

OK...I jumpered "on" the low speed fan and let it run for about 5 minutes. Stayed on with no problem. Also, remeasured resistance between 5 and 7. Just to be clear, my multi-meter was set for K-ohms...the reading was about 2.5, does this make sense?

So, my preliminary diagnosis is...on the A/C side...bad resistor (no low speed motor when jumped). On the oil cooler side, bad oil temp sensor or a CCU problem. I will pick up a sensor and a resistor for the AC side tomorrow (X-mas eve...not sure if dealership is open).

Is the resistor as difficult to access on the AC side (haven't looked in that side yet)? Can you describe its location?

If replacing temp sensor does not solve oil cooler side, I'll run a ground with 3 1.9ohm resistors in series and a small fuse to the number 6 leg of the oil cooler relay connector as you describe. The purpose here is to have the fan run on low, all the time. Please confirm that I've got it all straight.

With much appreciation,

Randall G.

Hi Mike,

&gt;When I took the readings, the car was off. Should I have measured the resistance between 5 and 7 with the ingition on?

You had it right--measure with the ignition off.

&gt;Also, since the oil temp sensor is now disconnected, will it still give correct readings?

Yes--they're different circuits. The temp. sensor is in series with the CCU, the resistor is in the relayed fan power supply circuit.

&gt;Just to be clear, my multi-meter was set for K-ohms...the reading was about 2.5, does this make sense?

Actually doesn't make sense--the resistance is too high. If you actually have 2.5 Kohms resistance in series with the motor, the motor will draw at best 12V/2500 ohms = 0.0048A. The slow-speed fan is supposed to draw around 9.5A. So, as you can imagine, 0.0048A isn't going to do much. I'm guessing you're probably reading the meter wrong, especially considering the fan ran in slow-speed for 5 minutes when jumpered.

One more approach is measuring the voltage between terminals #5/#7 with the fan jumpered in slow-speed. You should see about 4.2V, which is the voltage drop across the resistor. 4.2V//0.45 ohms = 9.3A. Give it a try, and let me know what you find.

&gt;So, my preliminary diagnosis is...on the A/C side...bad resistor (no low speed motor when jumped). On the oil cooler side, bad oil temp sensor or a CCU problem. I will pick up a sensor and a resistor for the AC side tomorrow (X-mas eve...not sure if dealership is open).

I think your diagnosis is right on track! While you're buying parts, you might consider picking up a relay as well ... just so you can positively rule it out as the problem.

&gt;Is the resistor as difficult to access on the AC side (haven't looked in that side yet)? Can you describe its location?

I can't really describe its location, other then it being attached to the sheet-metal (my resistors are both okay, so haven't had a need to personally get at 'em). I do understand it's much easier to replace than the oil cooler fan resistor.

&gt;If replacing temp sensor does not solve oil cooler side, I'll run a ground with 3 1.9ohm resistors in series and a small fuse to the number 6 leg of the oil cooler relay connector as you describe. The purpose here is to have the fan run on low, all the time. Please confirm that I've got it all straight.

Yes, you've got it straight. But, no need to actually use three individual 1.9 ohm resistors--I used three because that's what I had around the house (left over from university labs). I believe a single 5 ohm resistor should work, if that's all you can find.

Another option is installing a switch in wire G12, between the temp. sensor and CCU. Opening the switch would be analogous to disconnecting the temp. sensor, and would start the fan is fast-speed. I personally didn't take this approach because I wanted to take a completely non-invasive approach--no wires spliced, no holes drilled for a switch. I also wanted the fan to run automatically.

As a final option, Andial sells a switch kit that can be used to turn your fan on manually, as well. I believe it was really intended for people with functioning fans that wanted the option to start the fan manually when they felt the car was running too warm.

Talk to you soon!

MikeF

Randall,

Unfortunately, my two best sources for parts are both closed today. Looks like I'm stuck until Wednesday.

I do have another questions though...if I set up the ground lead with ~5ohms of resistance (I'm assuming the exact value isn't critical...pls confirm) it seems this would only work if the ballast resistor is operating within spec. Is this so? For lack of parts access today, I will try this. If this works, I may only try replacing the temp sensor and/or relay as the oil cooler ballast resistor is such a PITA to access.

I will re-measure the voltage between 5 and 7 with the low speed fan running via jumper wire and report back my voltage reading.
Also, since it seems these ballast resistors are troublesome by nature, is it worth replacing them even if they are working OK now?

Regarding the resistance measurement...my meter was definately set for K-ohms and the reading said 2.5 r. Even if I do the math using 2.5r the result still seems too low.

And yes, one other question...if I reattach the wire to the temp sensor, can I splice a switch into one of those leads? It seems this way, the fan will run on slow speed all the time (with #6 ground in place), and when I throw the switch, it would disconnect the sensor and the fan would go to high speed. I'm not so worried about the switch being located on my dashboard as it would get used rarely...I think I'd just use a standard switch and mount it underneath the dash. Any thoughts?

Randall G.

Hi Mike,

I believe a 5 ohm resistor will work fine for the slow-speed jumper. Where you might get in trouble is if you used too large a value, and the voltage at terminal #6 was too high for the relay to reposition. I don't know the exact value it's suppose to reposition at, so that's why I tried to mimic the factory value as close as possible. Oh, and I didn't want just a straight wire to ground ... shorts to ground make me nervous .

&gt;it seems this would only work if the ballast resistor is operating within spec

Absolutely! The slow-speed jumper merely tricks the relay into thinking it has received a start-signal from the CCU. All other components must be operating correctly. This includes the relay. Thus, if the slow-speed jumper works for you, the relay must be okay.

&gt;Also, since it seems these ballast resistors are troublesome by nature, is it worth replacing them even if they are working OK now?

Both of mine are fine, and I've made no effort to replace. Two reasons--they're so difficult to get to, and at $45 each, the cost is not trivial.

Generally speaking, it seems 993s--especially '95' models--are more prone to resistor failure. Perhaps a change in supplier? Don't know ...

&gt;Regarding the resistance measurement...my meter was definately set for K-ohms and the reading said 2.5 r. Even if I do the math using 2.5r the result still seems too low.

I'm not sure what the "r" means on your meter. Would that signify a resistance reading in ohms? Anyway, let's see how your voltage test comes back ... I'm guessing you'll come back at around 4.2V, which is positive proof the resistor is working. Of course, that's besides the fact that your fan operated without stopping when jumpered.

&gt;if I reattach the wire to the temp sensor, can I splice a switch into one of those leads?

Yes, you can. If possible, you'll want to find the wire that goes to terminal #2 of the oil temperature sensor plug. Terminal #2 attaches to wire G12.

Instead of splicing at the sensor, you may want to pull the CCU, and splice back there in wire G12.

&gt;It seems this way, the fan will run on slow speed all the time (with #6 ground in place), and when I throw the switch, it would disconnect the sensor and the fan would go to high speed.

Exactly! That said, I'm of the opinion (based on my experience to date) that a fast-speed switch is unneeded if you have the fan running continuously in slow-speed. Perhaps in your hotter climate--or if you track the car--a fast-speed switch would be helpful?

BTW, the slow-speed jumper at terminal #6 can become a fast-speed jumper if you switch it to terminal #1. Might be helpful on track days, and saves having to pull the mudguard to get at the sensor.

Talk to you soon!

MikeF

Randall,

It seems our numbers just aren't working out. I measured the voltage between 5 and 7 with the jumper between 3 and 5 to run the low speed fan. The result I got was 34mV which is .034V. Just to confirm stability of my ballast resistor, I let the fan stay running in low speed for another 5+ minutes. No problem.

Rgds,