Youngs92

iTrader: (1)

I'm in need of assistance. 1992 Camaro RS 305 TBI converted to 1988 TPI Vin F. According to the GM manual for V8 Vin E, my stock fan setup was controlled by three switches: A/C pressure switch (where is this?), Coolant fan switch, and A/C control head. Swapping over to the 88 Vin F setup, the ECM appears to control the fans solely, but through the fan temp sensor and A/C pressure switch. Does this seem right?

Recently, I've been burning through fan relays, causing my fans to shut off and the car to overheat. Having dissected the relays, I found melting of the relay between connections D and F. The fan fuse hasn't burned out, so it would seem the issue is on the signal side. How would I diagnose if the problem is with my ECM or one of the switches? Thanks in advance.

formula1LE

iTrader: (3)

Are you using stock fans? Used or new? What is their amp draw?

Youngs92

iTrader: (1)

I'm using the stock dual fan setup. Not sure about amp draw but I should see signs on the relay if the brining out was caused by the fan motors right?

formula1LE

iTrader: (3)

Well, if the fans consistently draw close to the max fuse rating due to age, I imagine its possible the relay contact material is overheating to the point where they partially fuse to each other. I suspect there must be an unusually high inrush current which could be because of old fan motors. As they age and wear, they require more amperage to do the same amount of work. The sudden on/off can create spikes which are the most damaging to the relay contact material. Do you have an inductive amp probe by chance? I'd be curious to know what the inrush is when a fan(s) kicks on.

RamIt

Excuse me in advance as I am somewhat ignorant about fuel injected thirdgens.
The tpi was a dual fan setup with separate triggers and separate relays.
The tbi cars were single fans with single relays right?

In the conversion did they convert to the dual relays or are you powering both fans from the old single relay?

Youngs92

iTrader: (1)

I believe both fans are running off the same single fan relay that was on the TBI setup. They have run like that for nearly 7 years without issues though. I will try to snag a probe from work. How would I go about measuring the amperage on those fans?

MoJoe

iTrader: (5)

One fan = one relay. Two fans = two relays. One relay for each fan. Sounds like you are pulling two fans worth of current (2x25a) through one relay rated for 30-40a.

Perhaps the original relay was better quality than the current replacements explains why they are burning out more frequently.

Youngs92

iTrader: (1)

Makes sense. Is there a simple way to wire the second relay in? Would it be best to order a dual fan harness and splice that in?

Also, if the fans were overloading the relay, I should see burning or melting on the fan motor side of the relay right? I'm not seeing that at the moment. I know I should have a second relay but I'm thinking that may be unrelated to how the relay is currently failing

formula1LE

iTrader: (3)

Keep in mind those original style cooling fans are an archaic design in terms of efficiency-if they draw anything close to 25A each I'd upgrade to a more modern fan setup. Not to mention the terrible shroud design. For example, an RF24 Motorcraft T-Bird fan draws on average 14-16 amps on low speed and 22-24 on high speed. And, those fans pull approx. 4200 CFM on high speed which is a hurricane compared to the TBI fans.

Nevertheless, you should have an inline fuse somewhere that should blow if the amperage gets exceedingly high. My guess is that the motor bearings are getting trashed which is making them fight the rotation.