Cooling fans don't stay on - keep cycling too soon I think.

[Timebender]

This seems to be a more recent development - since I put in a fanzilla and then took it out recently, as well as a new thermostat. Before the Fanzilla, the fans came on fine at 220 and stayed on for a while until the temp dropped below the 220 line.
After the Fanzilla was removed, and I went back to the fan relay - roughly a new one that was put a year and half ago, and the jumper for the fan fail, the fans now cycle on and then off when it hits 220, but only stay on for 5 minutes or so, then go off for about 5 minutes, then back on, and the temperature slowly climbs north of 220. I did bleed the system to make sure there's no air, and the otterstat is also fairly new - that and the relay were installed at the beginning of last year.

So I replaced the circuit breakers today, but still the same thing. 220 and they come on briefly, shut off, then come back on.

Any ideas?

I'm waiting for the coolant line to cool off before testing the otterstat.

[Bitsyncmaster]

The otterstat is designed to turn the fans on slightly above the opening of the thermostat. It may be your thermostat is opening at to high a temperature. I think it should open about 190 deg. F. Just not sure how accurate your dash temp gauge may be.

With the car just at idle, you should be able to feel the cooling hose on the drivers side heat up suddenly when the thermostat opens. Then watch the gauge climb a little and hear the fans turn on. Then you see the temp gauge drop a little and the fans turn off.

[Timebender]

The thermostat is set to open at 180 - I do think my gauge though isn't accurate. But after a while I do feel the water in the hose heat up to the otterstat, but even then the fans don't come on for a while - literally around 10 minutes once my gauge shows about 220 (which might be off 10 degrees). Then they come on, and it stays there, and in the past they'd stay on to keep it there. Now they shut off intermittently and the gauge climbs more.

I've bled the system, new circuit breakers, etc. I'll check the otterstat today when i get a chance, but I did go ahead and order one that starts at a lower temp from John.

[David T]

Regardless of what relay you use, the fans are turned on and off by the otterstat switch unless the circuit breaker is popping and resetting which it shouldn't if you have the uprated one installed. The thermostat is supposed to be 180 degrees and you must have the system bled of air. The temp gauge is not all that accurate especially if the motor was overheated or the electrical connections are dirty or loose. Use a non-contact infra-red temp gauge to check temp or a thermometer stuck into the header tank directly. The fans should start up above 180 but below 220. Once you start driving they don't come on over about 30 MPH unless you are running the A/C. If you have a Fanzilla you should use it. Get a meter on the output of the circuit breaker or just a light bulb and make sure the circuit breaker is not tripping.

[Ron]

FWIW- The manual A:01:01 calls for a 185-192F thermostat. i90F & 191F are easy to find.
(I believe they want it warmer than common 180F for the O2 sensor/Lambda sys....)

[Timebender]

Thanks guys. I got a new circuit breaker locally, 40 amp, at an RV place and it went right in the same spot. One thing for those who don't know my car (by now) is it has a Chevy 350 small block. However it had not been having issues until the old thermostat stopped working and was closed shut. I don't think that could've affected the otterstat, but I'll test it and see if the fans stay on until I disconnect the jumper.

And I'll put the fanzilla back in - though I did notice my passenger fan is running slower than the driver one - the driver one you can feel pulling air, the other one you can see spinning but not fast enough to do any help. And that caused the fuse in the fanzilla to pop on the right side.

So may need a new fan and could be a bad otterstat too. Also I'll see if one of my buddies has the temp sensor I can borrow.

[Timebender]

I'm going to guess it's my passenger side fan causing the issue. I jumped the otterstat and both fans came on as expected though I as I had mentioned previously, that one was running slow. About 3 minutes into running, the circuit breaker tripped and they shut off. It was hot as well as the wires to it, so my guess is the slow fan is drawing way too many amps (correct me if my electrical knowledge is wrong) thus the heat and the cb shutting off.

Now to get it up in the air to check the connections, and even maybe replace it.

Greg

[Timebender]

Update: I disconnected the passenger fan where it's connected at the fan fail socket, and thus the bigger fan (why they put a smaller on one the passenger side I don't know), not only ran faster, but kept the car running at just above the 220 mark, which is when my fans come on (at 220). Being that the otterstat connects the circuit at 180-ish, my guess is my temp sender in the 350 is not in sync with the gauge, or I need a new one. In either case, the fan came on and kept running for until I shut the engine off. Also, the circuit breaker stayed cool to the touch.

Now to get it on a rack somewhere and put in a new fan on the passenger side, as that should keep the car running even a bit cooler, especially on 95-105% degree days.

Thanks for everyone's help too!

Greg

[Bitsyncmaster]

Do you have OEM DeLorean fans?

[Timebender]

Do you have OEM DeLorean fans?

I don't think so as this has a much larger radiator. One is kinda big with a shroud on the driver side, and the passenger side could be the same size but doesn't have a shroud.

I checked the temperature with a laser/IR sensor and it reads mostly 160 when the temp gauge hits 220 (and the fan came on). As the gauge climbed slightly above 220, the sensor was showing 175-180 pointed at the top of the engine, and about 170 pointed at the thermostat outlet.

So, overall not to bad, and my gauge is way off... the good thing is the engine is designed to run much hotter being a 350sbc. The one time it got much hotter (almost at the 2nd red mark on the gauge) when the fans weren't coming on due to a bad thermostat, worst thing that happened was the car puked a good portion of coolant when i shut off the engine.

[DMCMW Dave]

I've run across a few cars where the gauge reads consistently 20-30 degrees hotter than reality. Scary until you spend enough time with an IR thermometer to convince yourself of the new "normal". Ideally you'd replace the gauge but most people won't spend the money.

[Timebender]

I plan on getting a new binnacle sometime down the road- so that will be a perfect time to replace the temp gauge (can it be calibrated?) and fuel gauge too as it's never accurate, even with a new sender (and all that was tested).

[DMCMW Dave]

I plan on getting a new binnacle sometime down the road- so that will be a perfect time to replace the temp gauge (can it be calibrated?) and fuel gauge too as it's never accurate, even with a new sender (and all that was tested).

There is a calibration shunt resistor on the back of each gauge. Factory calibrated but I'm sure if you are creative you could mess with it. You should not have to, the calibration is to overcome variations in the meter, not in the car.

I know, for sure that when the resistor fails on the gas gauge, it still works but is off by about 50%. Having a bunch of old ones around is an advantage though.

[Bitsyncmaster]

It could be the sender and or bad connection affecting gauge accuracy. I would think you could buy a new sender and run some tests by connecting the new sender to the car and putting that sender in some boiling water to see what the gauge reads.