1991 Other Oldsmobile Models Cooling fans won't turn on.

BRIANSNYDER

MEMBER
1991 OLDSMOBILE
6 CYL
FWD
AUTOMATIC
200,000 MILES

I have a 91 olds 98 regency. The radiator cooling fans won't turn on at all. I have rerplaced the tempeture sensor and temp swith and still they haven't turned. As you know this causes my engine tempeture to rise when I, m in stop and go traffic or sitting at an idle. I need to know what other things could be wrong and where they're located. Any help would be great. Is there any way I can test the fans themselves? Thanks

5 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Did you check both fuses no.4 40amp and fuse no.16 10amp-if these fuses are okay and you've replace CTS. Its coming from the computer relay control high/low or the fan relay itself.

Checking the fan. Right cooling fan motor connect a jumper wire from the battery positive post to the red and blue wire at the fan connector and black wire to the negative battery post. Fan comes On -its either the computer or the relay.

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Thursday, June 5th, 2008 AT 4:33 PM

BRIANSNYDER

MEMBER
4 POSTS

I checkeed the fuses first, all good. The fan works, thanks for telling me which wires are pos. And neg. So it must be the relay or a comp. Problem. I would like to know which relay controls the fan? There are 6 relays under the maxfuse/relay center panel under the hood. I checked the one directly under the 40 amp fuse, but it wasn't it. I am having trouble getting some of them off without cracking them. Is there any secret trick, and which one is the exact relay? Thanks a bunch for your help so far.

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Thursday, June 5th, 2008 AT 7:24 PM

RASMATAZ

MECHANIC
75,992 POSTS

See 8 and 9 fan Hi/Low relays below

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Friday, June 6th, 2008 AT 2:51 PM

BRIANSNYDER

MEMBER
4 POSTS

I checked the relay and its not it. I jumped the red main wire and the black/red wire at the relay and the fans turned on. I checked the brown wire with my multimeter and it has power with ignition on. Autozone. Com said it was either an open circuit or an ecm ground, but I have no idea where to look for those. Is there any way to ground the ecm again and where is the ecm located and the ground for it? You've been a ton of help so far. I might just wire the fan manualy, but I don't want to damage anything on the computer. I just think its wierd that if it is a bad ground there is no diagnostic light coming on. Thanks again.

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Saturday, June 7th, 2008 AT 9:25 PM

RASMATAZ

MECHANIC
75,992 POSTS

Troubleshoot the fan circuit see below-The computer grounds the relay-when it sees the coolant temperature sensors input signal requiring the fan to come On.