I have a strange issue with my new fan kit from MSA. When I drive in traffic, the temperature gauge reads normal for the car, with the needle in the E on the TEMP scale. When I drive on the highway, the needle creeps up almost to the P on the TEMP scale. I think that what is happening is that the fans don't spin fast enough to allow air to pass through them at highway speeds, and are effectively blocking the airflow. As an experiment, I unplugged the left side fan, and it stayed cooler on the highway, with the needle barely reaching the M on the TEMP scale. When I got back in traffic, the needle crept up towards the P, though. I plugged the left fan back in, and the temp went back into the E range, until I got back on the highway, when it went back towards the P again. I think the fan freewheels when it is unplugged, allowing more air to flow through it at highway speeds, but when I'm in stop/go traffic only having one fan running isn't enough. An alternative theory is that on the highway with both fans running, it somehow blows air in just the right way to heat up the sender for the temp gauge, which gives me a false high temp reading. I called MSA, and they basically said they've never heard of my problem before, and have no idea.

Attached is a picture showing how the two fans and shroud compare to the stock fan. A quick review is that directions are not step by step, but I figured out how to get it working easy enough. It's also not plug and play by any means, as you will have to completely fab up the wiring harness. They give you enough connectors to do it, but you'll need your own wires and flexible conduit if you want that. It does not compare at all to the quality and craftsmanship of Dave's headlight relay kits. Other than that, I will say this is a nice enough kit. The nice custom shroud isn't something most people could make themselves, although the rest of it can be bought off the shelf at Autozone.

If I can get the strange near overheating behavior figured out, I'll writeup how to install this thing, complete with pics. Does anyone have any ideas, or am I on track with the airflow issue? If it's an airflow issue, maybe I've just got a bad set of fans that can't spin fast enough? I know they get enough power, being wired right to the battery (but triggered by a relay).

Some additional info is that I did not have overheating problems before I put on the fan kit. I put it on because I wanted to improve the flow across the AC condenser. My old mechanical fan clutch wasn't engaging fully, either. Plus, I didn't have a shroud. I figured could get a new clutch and a shroud and hope it helped my AC cool better, or go with this kit. Since installing the kit, my AC blows nice and cold. Now I'm worried about overheating the engine though...

Thanks,

Matt

Edited September 15, 201113 yr by ConchZ

These are likely permanent magnet motors which means they act as generators when pushed. A short circuit or load across them will make them hard to turn. The battery and alternator become this load if the roadspeed is sufficient to push the fans faster than the supplied electric power.

If the two motors are in parallel then one will shunt the other when there is no power applied. Your test of unplugging one seems to prove this out. This would be most probable if one fan is wired in reverse polarity compared to the other. Is it possible that one fan is running backwards (pushing air toward the front of the car)?

As you point out, you've added more resistance to flow through the radiator when you went to electric fans. This can cause air to take the path of least resistance and go around the rad rather than through it at highway speeds. How does your fan support look? I noticed in your photos that the air duct on the carb side of the engine is missing. This is a great path for air to go around the rad.

As a quick and easy test, you might try temporarily taping up any holes you have on the rad support and see if the problem improves. You are trying to get every little bit of air that comes in the grill to go through the rad rather than around it.

Edited September 15, 201113 yr by steve91tt

I have the same kit and haven't had any of these problems. My temp gauge gets to just a degree to the right past straight up. Your fans shouldn't be running on the highway. Mine only do if stopped in traffic for a short while. On occasion, mine will get closer to hot if the the car has been sitting a while. I think I have a rogue air bubble.

Thanks guys, those are all good ideas, and maybe Beermanpete has led me to a possible answer.

If the two motors are in parallel then one will shunt the other when there is no power applied. Your test of unplugging one seems to prove this out. This would be most probable if one fan is wired in reverse polarity compared to the other. Is it possible that one fan is running backwards (pushing air toward the front of the car)?

They are both blowing the same way.

These are likely permanent magnet motors which means they act as generators when pushed. A short circuit or load across them will make them hard to turn. The battery and alternator become this load if the roadspeed is sufficient to push the fans faster than the supplied electric power

I agree that this is why the fans can become a blockage to airflow on the highway. I just think they should be designed to spin fast enough under power to avoid this happening. Perhaps I'm not getting enough power to them from the relay? I'll have to dig out the volt meter when I get home. It's possible I have a weak connection somewhere in my homemade wire harness.

I noticed in your photos that the air duct on the carb side of the engine is missing. This is a great path for air to go around the rad.

As a quick and easy test, you might try temporarily taping up any holes you have on the rad support and see if the problem improves. You are trying to get every little bit of air that comes in the grill to go through the rad rather than around it.

I guess those were old pictures, because I put an air duct on a couple of years ago. The radiator support does have the usual amount of holes in it, although the biggest ones are partially filled already by AC piping and wire conduit. If the cooling capacity is so borderline that these holes are critical, then this electric fan setup isn't going to be good enough on extremely hot days and/or very long drives.

Your fans shouldn't be running on the highway.

I don't know how they turn off on the highway. The only switches they have is the one connected to the AC and the one connected to a thermal probe pushed into the radiator. I guess that ideally there would be enough airflow on the highway to cool the radiator below the threshold of the thermal probe, and they would turn off. That isn't working for me, because my temp goes up when I get on the highway.

Again, thanks for the input. It helps to talk these things through with other folks.

I doubt the fans will run fast enough to keep up with a 70 MPH wind.

Does the problem occur when the AC is on, off, or both? When the AC is off the fans should be off and therefore be able to freewheel.

If the fans need to freewheel while the power is applied, a diode in series with each fan would do that (at the expense of a volt or so).

I doubt the fans will run fast enough to keep up with a 70 MPH wind.

Does the problem occur when the AC is on, off, or both? When the AC is off the fans should be off and therefore be able to freewheel.

If the fans need to freewheel while the power is applied, a diode in series with each fan would do that (at the expense of a volt or so).

The problem happens when the AC is on or off. I think the fans stay on because by the time I get on the highway, the temp is warm enough to trigger their switch. Once they are running, they can't freewheel, and they block air on the highway, and the temp never falls far enough to turn off their switch. I have been reading a bit about diodes with electric fans, and agree that you need one. I see that they are often included inside the relay, to protect the relay from power spikes that happen when the fan freewheels. Interestingly, the relay in my kit was different than the relay that MSA normally includes. Usually, the relay has a metal mounting bracket, and mine did not. I suspect it also does not have this diode.

Here's a question. I have noticed that my amp meter moves farther towards the positive the faster I go. It's always done this of course, but it now seems to go a bit farther than it used to go. Would this be a result of the fans trying to freewheel, generating electricity as they do so?

A quick update. I did install a freewheeling diode on the postive side of the fans, with a branch from it that takes it to ground, per some instructions on electric fan installation I found elsewhere. This seems to have cured the problem. However, by the time I did this, the hot days had ended, so I'm not sure. Will likely not know until next summer. I hope I have sovled the mystery, because these fans definitely help your AC cool better.