Help Diagnose Fan Issue on 2007 Elise (Low Speed works High Speed Does Not) - LotusTalk - The Lotus Cars Community
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post #1 of 2 (permalink) Old 08-22-2018, 03:25 PM Thread Starter
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Help Diagnose Fan Issue on 2007 Elise (Low Speed works High Speed Does Not)

Hi there, I will be taking my car to the Lotus service center in my area (Lotus/Aston Martin of New England), but I thought I'd ask for some help with things I might suggest that they take a look at, since both I, and they have had trouble diagnosing my exact problem -- the car has been in a few times for various issues surrounding the radiator fans.

2 years ago, I had the car in for a service and some paintwork as my driver's side door needed replacement after a truck backed into it in a parking lot. After I got the car back, on the way home, it came very close to overheating (flashing 225 temp) when I hit some stop-n-go traffic on an excruciatingly hot day in Boston. The traffic let up just as the temp gauge started flashing and I was able to get moving enough that the car cooled down on its own with airflow going over the radiator. I didn't know what the problem was at the time, but I took it back and they diagnosed a bad fan control module. As is fairly common, part of it had burned up/melted at the connector.

They ordered a new fan control module for me, but since the connector had burned up a bit, they had to get both another connector and also some additional bits of wiring harness from a donor car that they had in the shop to replace a melted section of wire.

After that, the fans would come on, as expected, except that I noticed shortly thereafter that only one of the fans was turning on. It turned on when the temp hit a certain point, and turned itself off once the temp came down, and it would also turn on shortly after I would turn on the air conditioner (but not immediately when turning it on.)

I took the car back in to the shop, and they couldn't pinpoint the issue. They were able to fire both fans from the computer that it was hooked up to, so they re-checked the connections to the fan control module, sent me on my way, and it appeared to be working again, at least temporarily, both fans appeared to be working.

Shortly thereafter again, I noticed that only one fan seemed to be engaging (I.e. could feel airflow on one side but not the other). I started doing some research on it, and I figured I would do what I could before taking it back again.

I replaced both fuses (I believe, 14 and 19 from memory.)

This seemed to solve at least one problem -- both fans now came on, and they both come on immediately when I turn on the air conditioner. I thought this had fixed the problem as I don't ever recall the fans working like this (I.e. in low-speed) and it seemed to help a lot around town, etc., and I thought the issue was sorted and it was just a faulty fuse (neither of the fuses I replaced were blown, I just installed fresh ones to start narrowing down possibilities.)

Fast forward to yesterday -- I was driving from Boston --> North Carolina/Tennessee to drive the Tail of the Dragon, everything was going great -- until I hit some standstill NYC traffic in 90+ degree heat while in line for the GW Bridge - and I realized that while the fans were operating in low-speed mode, they were not switching to high-speed mode and they could not keep up with keeping the car cool, with or without the AC turned on (it could do a better job with the AC turned off, of course) -- as I was waiting in line, it hit 225 again and started flashing -- and I had basically nowhere to go since I really needed to get on the GW bridge. However, car safety comes first - so I pulled off on 9A so that I could get the car moving again with some airflow and it went back down to 200 and under very quickly.

I ended up getting in line for the Holland tunnel now that the car was back down to around 200 - but it went right back up to 225 while in the stop-n-go tunnel traffic, and hit 225 and flashing (thankfully) right as I was exiting the tunnel and was able to get moving again for more airflow.

Please note, that in any other circumstances, I would have pulled over and let the car cool down for a while before I kept going -- but I was in NYC in rush-hour and it was literally just about impossible for me do do anything about the problem while I was in the car.

Finally, I pulled off at a service center to let the car cool down, and rather than continue my journey, I decided to return home a few hours later when traffic lightened up and temps cooled down. The drive home was uneventful and fine as the car cools itself totally fine when it's moving and not in stop-n-go traffic with high external temps.

So anyhow, I plan to take the car in this week. Any ideas on things I should ask them to look for?

1. Both fans operate in low speed mode, but they will not switch over to high speed mode
2. Fans will come on when AC is switched on
3. Fans will automatically turn themselves off when temps come down
4. Fan Control Module has been replaced
5. 14 & 19 Fuses have been replaced

I know that the fans are not turning on at high-speed, but should I also have things like the thermostat replaced just as a precaution?


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post #2 of 2 (permalink) Old 08-22-2018, 07:17 PM
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Join Date: Nov 2015
Location: massachusetts
Posts: 2,134
IIRC the fans work in series or parallel so low they are in series high they are in parallel thus if only one fan is working it is probably a bad fan
My car I only see high fan with ac in very hot weather
I am thinking with one fan working it allows the car to get hotter and want high fan when normally it wouldn’t

Also a bad fan could blow the switch pack relay

I cannot work it out in my head but I am thinking there is a way one connection could be missing that would cause one fan to run low and not have high fan
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